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Thyroid Disease Manager : Diagnosis and Treatment of Graves

Diagnosis of the classic form of Graves disease is easy and depends on the recognition of the cardinal features of the disease and confirmation by tests such as TSH and FTI. The differential diagnosis includes other types of thyrotoxicosis, such as that occurring in a nodular gland, accompanying certain tumors of the thyroid, or thyrotoxicosis factitia, and nontoxic goiter. Types of hypermetabolism that imitate symptoms of thyrotoxicosis must also enter the differential diagnosis. Examples are certain cases of pheochromocytoma, polycythemia, lymphoma, and the leukemias. Pulmonary disease, infection, parkinsonism, pregnancy, or nephritis may stimulate certain features of thyrotoxicosis. Treatment of Graves disease cannot yet be aimed at the cause because it is still unknown. One seeks to control thyrotoxicosis when that seems to be the major indication, or the ophthalmopathy when that aspect of the disease appears to be more urgent. The available forms of treatment, including surgery, drugs, and 131-I therapy, are reviewed. There is a difference of opinion as to which of these modalities is best, but to a large degree guidelines governing choice of therapy can be drawn. Antithyroid drugs are widely used for treatment on a long- term basis. About one-third of the patients undergoing long-term antithyroid therapy achieve permanent euthyroidism. Drugs are the preferred initial therapy in children and young adults. Subtotal thyroidectomy is a satisfactory form of therapy, if an excellent surgeon is available, but is less used in 2016. The combined use of antithyroid drugs and iodine makes it possible to prepare patients adequately before surgery, and operative mortality is approaching the vanishing point. Many young adults, are treated by surgery if antithyroid drug treatment fails. Currently, most endocrinologists consider RAI to be the best treatment for adults, and consider the associated hypothyroidism to be a minor problem. Evidence to date after well over five decades of experience indicates that the risk of late thyroid carcinoma must be near zero. The authors advise this therapy in most patients over age 40, and believe that it is not contraindicated above the age of about 15. Dosage is calculated on the basis of 131-I uptake and gland size. Most patients are cured by one treatment. Hypothyroidism.occurs with a fairly constant frequency for many years after therapy and may be unavoidable if cure of the disease is to be achieved by 131-I.. Many therapists accept this as an anticipated outcome of treatment. Thyrotoxicosis in children is best handled initially by antithyroid drug therapy. If this therapy does not result in a cure, surgery may be performed. Treatment with 131-I is accepted as an alternative form of treatment by some physicians, especially as age increase toward 15 years. Neonatal thyrotoxicosis is a rarity. Antithyroid drugs, propranolol and iodide may be required for several weeks until maternally-derived antibodies have been metabolized. The physician applying any of these forms of therapy to the control of thyrotoxicosis should also pay heed to the patients emotional needs, as well as to his or her requirements for rest, nutrition, and specific antithyroid medication. Consult our FREE web-book http://WWW.ENDOTEXT.ORG for complete coverage on this and related topics.

We note that there are currently available 2 very extensive Guidelines on Diagnosis and Treatment of Graves DiseaseThe 2016 ATA guideline (270 pages), and the AACE 2011 version on Hyperthyroidism and other Causes of Thyrotoxicosis (65 pages) Both are well worth reviewing.

The diagnosis of Graves disease is usually easily made. The combination of eye signs, goiter, and any of the characteristic symptoms and signs of hyperthyroidism forms a picture that can hardly escape recognition (Fig -1). It is only in the atypical cases, or with coexisting disease, or in mild or early disease, that the diagnosis may be in doubt. The symptoms and signs have been described in detail in the section on manifestations of Graves disease. For convenience, the classic findings from the history and physical examination are grouped together in Table 1a and 1b.These occur with sufficient regularity that clinical diagnosis can be reasonably accurate. Scoring the presence or absence and severity of particular symptoms and signs can provide a clinical diagnostic index almost as reliable a diagnostic measure as laboratory tests(1).

Occasionally diagnosis is not at all obvious.In patients severely ill with other disease, in elderly patients with apathetic hyperthyroidism, or when the presenting symptom is unusual, such as muscle weakness, or psychosis, the diagnosis depends on clinical alertness and laboratory tests.

The diagnosis of Graves Disease does not only depend on thyrotoxicosis. Ophthalmopathy, or pretibial myxedema may occasionally occur without goiter and thyrotoxicosis, or even with spontaneous hypothyroidism. While proper classification can be debated, these patients seem to represent one end of the spectrum of Graves Disease. Thus we are usually making two coincident diagnoses:1)- Is the patient hyperthyroid? and 2)- Is the cause of the problem Graves disease ?.

Family history of any thyroid disease, especially Graves disease

TSH and FT4 assay-Once the question of thyrotoxicosis has been raised, laboratory data are required to verify the diagnosis, help estimate the severity of the condition, and assist in planning therapy. A single test such as the TSH or estimate of FT4 (free T4) may be enough, but in view of the sources of error in all determinations, most clinicians prefer to assess two more or less independent measures of thyroid function. For this purpose, an assessment of FT4 and sensitive TSH are suitable. As an initial single test, a sensitive TSH assay may be most cost-effective and specific. TSH should be 0 .1 U/ml in significant thyrotoxicosis, although values of .1 .3 are seen in patients with mild illness, especially with smoldering toxic multinodular goiter in older patients(1.1). TSH can be low in some elderly patients without evidence of thyroid disease. TSH can be normal or elevated only if there are spurious test results from heterophile antibodies or other cause, or the thyrotoxicosis is TSH-driven, as in a pituitary TSH-secreting adenoma or pituitary resistance to thyroid hormone. Measurement of FT4 or FTI (Free thyroxine index)is also usually diagnostic.The degree of elevation of the FT4 above normal provides an estimate of the severity of the disease. During replacement therapy with thyroxine the range of both FTI and fT4 values tend to be about 20% above the normal range, possibly because only T4, rather than T4 and T3 from the thyroid, is providing the initial supply of hormone. Thus many patients will have an fT4 or FTI above normal when appropriately replaced and while TSH is in the normal range. Except for this, elevations of fT4 not due to thyrotoxicosis are unusual, and causes are given in Table 3.

Of course the Total T4 level may normally be as high as 16 or 20 g/dl in pregnancy, and can be elevated without thyrotoxicosis in patients with familial hyperthyroxinemia due to abnormal albumin, the presence of hereditary excess TBG, the presence of antibodies binding T4 , the thyroid hormone resistance syndrome, and other conditions listed in Table 3. The T4 level may be normal in thyrotoxic patients who have depressed serum levels of T4 -binding protein or because of severe illness, even though they are toxic. Thus, thyrotoxicosis may exist when the total T4 level is in the normal range. However measurement of FT4, FT3 (Free T3), or FTI (Free Thyroxine Index) usually obviates this source of error and is the best test. In the presence of typical symptoms, one measurement of suppressed TSH or elevated fT4 is sufficient to make a definite diagnosis, although it does not identify a cause. If the fT4 is normal, repetition is in order to rule out error, along with a second test such as serum FT3. And it should be noted that in much of Europe FT3 is the preferred test, rather than FT4, and serves very well.

A variety of methods for FT4 determination have become available, including commercial kits. Although these methods are usually reliable, assays using different kits do not always agree among themselves or with the determination of FT4 by dialysis. Usually T4 and T3 levels are both elevated in thyrotoxicosis, as is the FTI (Free Thyroxin Index), or an index constructed using the serum T3 and rT3U levels, and the newer measures of FT3.

T3 and FT3 ASSAY-The serumT3 level determined by RIA is almost always elevated in thyrotoxicosis and is a useful but not commonly needed secondary test. Usually the serum T3 test is interpreted directly without use of a correction for protein binding, since alterations of TBG affect T3 to a lesser extent than T4. Any confusion caused by alterations in binding proteins can be avoided by use of a FT3 assay or T3 index calculated as for the FTI. Generally the FT3 assay is as diagnostically effective as the FT4. In patients with severe illness and thyrotoxicosis, especially those with liver disease or malnutrition or who are taking steroids or propranolol, the serum T3 level may not be elevated, since peripheral deiodination of T4 to T3 is suppressed (T4 toxicosis). A normal T3 level has also been observed in thyrotoxicosis combined with diabetic ketoacidosis. Whether or not these patients actually have tissue hypermetabolism at the time their serum T3 is normal is not entirely certain. In these patients the rT3 level may be elevated. If the complicating illness subsides, the normal pattern of elevated T4 , FTI, and T3 levels may return(5,6). Elevated T4 levels with normal serum T3 levels are also found in patients with thyrotoxicosis produced by iodine ingestion(7).

T3 Toxicosis Since 1957, when the first patient with T3 thyrotoxicosis was identified, a number of patients have been detected who had clinical thyrotoxicosis, normal serum levels of T4 and TBG, and elevated concentrations of T3 and FT3[8]. Hollander et al [9] found that approximately 4% of patients with thyrotoxicosis in the New York area fit this category. These patients often have mild disease but otherwise have been indistinguishable clinically from others with thyrotoxicosis. Some have had the diffuse thyroid hyperplasia of Graves disease, others toxic nodular goiter, and still others thyrotoxicosis with hyperfunctioning adenomas. Interestingly, in Chile, a country with generalized iodine deficiency, 12.5% of thyrotoxic subjects fulfilled the criteria for T3 thyrotoxicosis [10]. Asymptomatic hypertriiodothyronemia is an occasional finding several months before the development of thyrotoxicosis with elevated T4 levels [11]. Since T4 is normally metabolized to T3, and the latter hormone is predominantly the hormone bound to nuclear receptors, it makes sense that elevation of T3 alone is already indicative of thyrotoxicosis.

Thyroid Isotope uptake-In patients with thyrotoxicosis the RAIU (Radioactive Iodine Uptake) at 24 hours is characteristically above normal. In the United States, which has had an increasing iodine supply in recent years, the upper limit of normal is now about 25% of the administered dose. This value is higher in areas of iodine deficiency and endemic goiter. The uptake value at a shorter time interval, for example 6 hours, is as valid a test and may be more useful in the infrequent cases having such a rapid isotope turnover that uptake has fallen to normal by 24 hours. If there is reason to suspect that thyroid isotope turnover is rapid, it is wise to do both a 6- and a 24-hour RAIU determination during the initial laboratory study. As noted below, rapid turnover of 131-I can seriously reduce the effectiveness of 131-I therapy. Similar studies can be done with 123-I and also technetium. Because of convenience, and since serum assays of thyroid hormones and TSH are reliable and readily available, the RAIU is now infrequently determined unless 131-I therapy is planned.. It is however useful in patients who are mildly thyrotoxic for factitia thyrotoxicosis, subacute thyroiditis and painless thyroiditis in whom RAIU is low, thus confirming thyrotoxicosis in the absence of elevated RAIU. This may include patients with brief symptom duration, small goiter, or lacking eye signs, absent family history, or negative antibody test result. Obviously other causes of a low RAIU test need to be considered and excluded. Tests measuring suppressibility of RAIU are of historical interest(13-15)

Thyroid IsotopeScanning-Isotope scanning of the thyroid has a limited role in the diagnosis of thyrotoxicosis. It is useful in patients in whom the thyroid is difficult to feel or in whom nodules (single or multiple) are present that require evaluation, or rarely to prove the function of ectopic thyroid tissue. Nodules may be incidental, or may be the source of thyrotoxicosis (toxic adenoma), or may contribute to the thyrotoxicosis that also arises from the rest of the gland. Scanning should usually be done with 123-I in this situation, in order to combine it with an RAIU measurement.

Thyroid Ultrasound- US exam of the thyroid is sometimes of value in diagnosis. For example, if a possible nodule is detected on physical exam. It also may confirm hypoechogenicity or intense vascularity of Graves disease if a color Doppler flow exam is done.

Antithyroid Antibodies Determination of antibody titers provides supporting evidence for Graves disease. More than 95% of patients have positive assays for TPO (thyroperoxidase or microsomal antigen), and about 50% have positive anti-thyroglobulin antibody assays. In thyroiditis the prevalence of positive TG antibody assays is higher. Positive assays prove that autoimmunity is present, and patients with causes of thyrotoxicosis other than Graves disease usually have negative assays. During therapy with antithyroid drugs the titers characteristically go down, and this change persists during remission. Titers tend to become more elevated after RAI treatment.

Antibodies to TSH-Receptor-Thyrotrophin receptor antibody (TRAb) assays have become readily available, and a positive result strongly supports the diagnosis of Graves disease(15.1). Determination of TRAb is not required for the diagnosis, but the implied specificity of a positive test provides security in diagnosis, and for this reason the assay is now widely used. The assay is valuable as another supporting fact in establishing the cause of exophthalmos, in the absence of thyrotoxicosis. High maternal levels suggest possible fetal or neonatal thyrotoxicosis. TRAb assays measure any antibody that binds to the TSH-R. Assays for Thyroid Stimulating Antibodies (TSAb,TSI) are less available, but are more specific for the diagnosis. Using current tests, both are positive in about 90% of patients with Graves disease who are thyrotoxic. Second generation assays becoming available use monoclonal anti-TSH-R antibodies and biosynthetic TSH-R in coated tube assays, are reported to reach 99% specificity and sensitivity(15.2,15.3,3). Although rarely required, serial assays are of interest in following a patients course during antithyroid drug therapy, and a decrease predicts probable remission(15.4).

Other Assays Rarely Used-General availability of assays that can reliably measure suppressed TSH has made this the gold standard to which other tests must be compared, and has effectively eliminated the need for most previously used ancillary tests. There are only rare causes of confusion in the TSH assay. Severe illness, dopamine and steroids, and hypopituitarism, can cause low TSH, but suppression below 0.1 /ml is uncommon and below 0.05 /ml is exceptional, except in thyrotoxicosis. Thyrotoxicosis is associated with normal or high TSH in patients with TSH producing pituitary tumors and selective pituitary resistance to thyroid hormone. If TSH, FT4, TRAb, and other tests noted above do not establish the diagnosis, it may be wise to do nothing further except to observe the course of events. In patients with significant thyroid hyperfunction, the symptoms and signs will become clearer, and the laboratory measurements will fall into line. Measurement of BMR, T3 suppression of RAIU, TRH testing, and clinical response to KI are of historical interest.

Graves disease must be differentiated from other conditions causing thyrotoxicosis. (Table -4).

Thyrotoxicosis factitia-Thyrotoxicosis may be caused by taking T4 or its analogs, most commonly due to administration of excessive replacement hormone by the patients physician. Hormone may be taken surreptitiously by the patient for weight loss or psychologic reasons. The typical findings are a normal or small thyroid gland, a low131-I uptake, a low serum TG, and, of course, a striking lack of response to antithyroid drug therapy. The problem can easily be confused with painless thyroiditis, but in thyrotoxicosis factitia, the gland is typically small.

Toxic nodular goiter is usually distinguished by careful physical examination and a history of goiter for many years before symptoms of hyperthyroidism developed. The thyrotoxicosis comes on insidiously, and often, in the older people usually afflicted, symptoms may be mild, or suggest another problem such as heart disease. The thyroid scan may be diagnostic, showing areas of increased and decreased isotope uptake. The results of assays for antithyroid antibodies, including TRAb, are usually negative. TMNG is typically produced by activating somatic mutations in TSH-R in one or more nodules, allowing them to enlarge and become functional even in the absence of TSH stimulation. (Interestingly, cats are well known to develop hyperthyroidism, with thyroid autonomy, often due to TSH-R gene mutations as seen in humans.(16))

Hyperfunctioning solitary adenoma is suggested on the physical finding of a palpable nodule in a otherwise normal gland, and is proved by a scintiscan demonstrating preferential radioisotope accumulation in the nodule. This type of adenoma must be differentiated from congenital absence of one of the lobes of the thyroid. Toxic nodules typically present in adults with gradually developing hyperthyroidism and a nodule > 3 cm in size. These nodules are usually caused by activating somatic mutations in the TSH-R, which endows them with mildly increased function, compared to normal tissue, even in the absence of TSH. These nodules are usually, but not always, monoclonal(17). In adults toxic nodules are very rarely malignant. Rarely, functioning thyroid carcinomas produce thyrotoxicosis. The diagnosis is made by the history, absence of the normal thyroid, and usually widespread functioning metastasis in lung or bones. Invasion of the gland by lymphoma has produced thyrotoxicosis, presumably due to thyroid destruction (18).

Thyrotoxicosis associated with subacute thyroiditis is usually mild and transient, and the patient lacks the physical findings of long-standing thyrotoxicosis. If thyrotoxicosis is found in conjunction with a painful goiter and low or absent 131-I uptake, this diagnosis is likely. Usually the erythrocyte sedimentation rate (ESR) and CRP are greatly elevated, and the leukocyte count may also be increased. Occasionally the goiter is non-tender. Antibody titers are low or negative. Many patients have the HLA-B35 antigen, indicating a genetic predisposition to the disease. The rare TSH secreting pituitary adenoma will be missed unless one measures the plasma TSH level, or until the enlargement is sufficient to produce deficiencies in other hormones, pressure symptoms, or expansion of the sella turcica(19). These patients have thyrotoxicosis with inappropriately elevated TSH levels and may/or may not secrete more TSH after TRH stimulation. The characteristic finding is a normal or elevated TSH, and an elevated TSH alpha subunit level in blood, measured by special RIA. TRAbs are not present. Exophthalmos, and antibodies of Graves disease are absent. Family history is sometimes positive for a similar condition. Demonstration of a suppressed TSH level excludes these rare cases.

The category of patients with thyrotoxicosis and inappropriately elevated TSH levels also includes the rare persons with pituitary T3 resistance as a part of the Resistance to Thyroid Hormone syndrome caused by TH Receptor mutations. The syndrome of Pituitary Thyroid Hormone Resistance is usually marked by mild thyrotoxicosis, mildly elevated TSH levels, absence of pituitary tumor, a generous response to TRH, no excess TSH alpha subunit secretion [19,20, 21],and by TSH suppression if large doses of T3 are administered. Final diagnosis depends on laboratory demonstration of a mutation in the TR gene, if possible. Hyperthyroidism caused by excess TRH secretion is a theoretical but unproven possibiity.

Administration of large amounts of iodide in medicines, for roentgenographic examinations, or in foods can occasionally precipitate thyrotoxicosis in patients with multinodular goiter or functioning adenomas. This history is important to consider since the illness may be self-limiting. Induction of thyrotoxicosis has also been observed in apparently normal individuals following prolonged exposure to organic iodide containing compounds such as antiseptic soaps and amiodarone. Amiodarone is of special importance since the clinical problem often is the presentation of thyrotoxicosis in a patient with serious cardiac disease including dysrythmia. Amodarone can induce thyrotoxicosis in patients without known prior thyroid disease, or with multinodular goiter. The illness appears to come in two forms. In one the RAIU may be low or normal. In the second variety , which appears to be more of a thyroiditis-like syndrome, the RAIU is very suppressed, and IL-6 may be elevated. In either case TSH is suppressed, FTI may be normal or elevated, but T3 is elevated if the patient is toxic. Antibodies are usually negative.

An increasingly recognized form of thyrotoxicosis is the syndrome described variously as painless thyroiditis, transient thyrotoxicosis, or hyperthyroiditis. Its hallmarks are self-limited thyrotoxicosis, small painless goiter, and low or zero RAIU(22,23). The patients usually have no eye signs, a negative family history, and often positive antibody titers. This condition is due to autoimmune thyroid disease, and is considered a variant of Hashimotos Thyroiditis. It occurs sporadically, usually in young adults. It frequently occurs 3 12 weeks after delivery, sometimes representing the effects of immunologic rebound from the immunosuppressive effects of pregnancy in patients with Hashimotos thyroiditis or prior Graves Disease, and is called Post Partum Thyroiditis(22-25). The course typically includes development of a painless goiter, mild to moderate thyrotoxicosis, no eye signs, remission of symptoms in 3 -20 weeks, and often a period of hypothyroidism before return to euthyroid function. The cycle may be repeated several times. Histologic examination shows chronic thyroiditis, but it is not typical of Hashimotos disease or subacute thyroiditis and may revert to normal after the attack(26). In most patients, the thyrotoxic episode occurs in the absence of circulating TSAb. This finding suggests that the pathogenesis is quite distinct from that in Graves disease. The thyrotoxicosis is caused by an inflammation-induced discharge of preformed hormone due to the thyroiditis. The T4/T3 ratio is higher than in typical Graves disease,and thyroid iodine stores are depleted. Since the thyrotoxicosis is due to an inflammatory process, therapy with antithyroid drugs or potassium iodide is usually to no avail, and RAI treatment of course cannot be given when RAIU is suppressed. Propranolol is usually helpful for symptoms. Glucocorticoids may be of help if the process often transient and mild requires some form of therapy. Propylthiouracil and/or ipodate can be used to decrease T4 to T3 conversion and will ameliorate the illness. Repeated episodes may be handled by surgery or by RAI therapy during a remission. Occasionally painless post-partum thyroiditis is followed by typical Graves Disease(27-29.1).

Hyperemisis gravidarum is frequently associated with elevated serum T4 , FTI, and variably elevated T3, and suppressed TSH. The abnormalities in thyroid function are caused by high levels of hCG. This molecule, or a closely related form, share enough homology with TSH so that it has about 1/1000 the thyroid stimulating activity of TSH, and can produce thyroid stimulation or thyrotoxicosis(29.12-29.14). It is typically self limited without specific treatment, disappears with termination of pregnancy, but may occasionally require anti-thyroid treatment temporarily or throughout pregnancy(29.3). Patients with minimal signs and symptoms, small or no goiter, and elevation of FTI up to 50 % above normal probably do not require treatment. Rarely those with goiter, moderate or severe clinical evidence of thyrotoxicosis, highly elevated T4 and T3 and suppressed TSH are best treated with antithyroid drugs. If antibodies are positive or eye signs are present, the picture is usually interpreted as a form of Graves disease. Familial severe hyperemesis gravidarum with fetal loss has been reported with an activating germline mutation in the TSH-R, which made it specifically more sensitive to activation by hCG(.29.2,29.3). Hyperthyroidism can be induced by hyperplacentosis, which is characterized by increased placental weight and circulating hCG levels higher than those in normal pregnancy(29.4). After hysterotomy, hCG levels declined in the one case reported and hyperthyroidism was corrected.

Congenital hyperthyroidism caused by a germ-line activating mutation in the TSH-R has recently been recognized . The mutations are usually single aminoacid transitions in the extracellular loops or transmembrane segments of the receptor trans-membrane domain. The diagnosis may be difficult to recognize in the absence of a family history. However the patients lack eye signs, and have negative assays for antibodies(29.2, 29.3)

Hydatidiform moles, choriocarcinomas, and rarely seminomas secrete vast amounts of hCG. hCG, with an alpha subunit identical to TSH , and beta subunit related to TSH , that binds to and activates the thyroid TSH receptor with about 1/1,000th the efficiency of TSH itself (Fig.-3)(30-33). Current evidence indicates that very elevated levels of native hCG or perhaps desialated hCG, cause the thyroid stimulation. Many patients have goiter or elevated thyroid hormone levels or both, but little evidence of thyrotoxicosis, whereas others are clearly thyrotoxic. Diagnosis rests on recognizing the tumor (typically during or after pregnancy) and measurement of hCG. Therapy is directed at the tumor.

Hyperthyroidism also is seen as one manifestation of autoimmune thyroid disease induced by interferon-alpha treatment of chronic hepatitis C. It can be self limiting, or severe enough to require cessation of IFN, or in some cases continue on after INF is stopped(33.1).

Hyperthyroidism also occurs during immune reconstitution seen after effective anti-viral therapy of patients with HIV(33.2), has occurred during recovery of low lymphocyte levels induced by therapy with CAMPATH in patients with Multiple sclerosis, has occurred after cessation of immune-suppressive treatment in patients with T1DM.

It should be remembered that thyrotoxicosis is today not only a clinical but also a laboratory diagnosis. Consistent elevation of the fT4 , and the T3 level, and suppressed TSH, or only suppression of TSH, can indicate that thyrotoxicosis is present even in the absence of clear-cut signs or symptoms These elevations themselves are a sufficient indication for therapy, especially in elderly patients with coincident cardiac disease(33a,b). Antithyroid drug treatment of patients with subclinical hyperthyroidism was found to result in a decrease in heart rate, decrease in number of atrial and ventricular premature beats, a reduction of the left ventricular mass index, and left ventricular posterior wall thickness, as well as a reduction in diastolic peak flow velocity. These changes are considered an argument for early treatment of subclinical hyperthyroidism. Subclinical hyperthyroidism may disappear or evolve into Graves hyperthyroidism, or when caused by MNG, persist for long periods unchanged. Individuals of any age with consistent suppression of TSH should be fully evaluated to determine if evidence of hyperthyroidism is present, or there is coincident disease that might be aggrevated by hyperthyroidism. SCH with TSH of 0.2-0.3.5 may not need treatment. Individuals with TSH at or below 0.1uU/ml most likely will require treatment by one of the methods described below.

Apathetic hyperthyroidism designates a thyrotoxic condition characterized by fatigue, apathy, listlessness, dull eyes, extreme weakness, often congestive heart failure, and low-grade fever.[ 34, 35] Often such patients have small goiters, modest tachycardia, occasionally cool and even dry skin, and few eye signs. The syndrome may, in some patients, represent an extreme degree of fatigue induced by long-standing thyrotoxicosis. Once the diagnosis is considered, standard laboratory tests should confirm or deny the presence of thyrotoxicosis even in the absence of classical symptoms and signs.

Other diagnostic problems Two common diagnostic problems involve (1) the question of hyperthyroidism in patients with goiter of another cause, and (2) mild neuroses such as anxiety, fatigue states, and neurasthenia. Most patients with goiter receive a battery of examinations to survey their thyroid function at some time. Usually these tests are done more for routine assessment than because there is serious concern over the possibility of thyrotoxicosis. In the absence of significant symptoms or signs of hyperthyroidism and ophthalmologic problems, a normal FTI or TSH determination is sufficiently reassuring to the physician and the patient. Of course, the most satisfactory conclusion of such a study is the identification of an alternate cause for enlargement of the thyroid. Some patients complain of fatigue and palpitations, weight loss, nervousness, irritability, and insomnia. These patients may demonstrate brisk reflex activity, tachycardia (especially during examinations), perspiration, and tremulousness. In the abscence of thyrotoxicosis, the hands are more often cool and damp rather than warm and erythematous. Serum TSH assay should be diagnostic.

Mild and temporary elevation of the FTI may occur if there is a transient depression of TBG production for example, when estrogen administration is omitted. This problem is occasionally seen in hospital practice, usually involving a middle-aged woman receiving estrogen medication that is discontinued when the patient is hospitalized. Estrogen withdrawal leads to decreased TBG levels and a transiently elevated FTI. After two to three weeks, both the T4 level and the FTI return to normal ( Table -3). In the differential diagnosis of heart disease, the possibility of thyrotoxicosis must always be considered. Some cases of thyrotoxicosis are missed because the symptoms are so conspicuously cardiac that the thyroid background is not perceived. This is especially true in patients with atrial fibrillation. Many disorders may on occasion show some of the features of hyperthyroidism or Graves disease. In malignant disease, especially lymphoma, weight loss, low grade fever, and weakness are often present. Parkinsonism in its milder forms may initially suggest thyroid disease. So also do the flushed countenance, bounding pulse, thyroid hypertrophy, and dyspnea of pregnancy. Patients with chronic pulmonary disease may have prominent eyes, tremor, tachycardia, weakness, and even goiter from therapeutic use of iodine. One should remember the weakness, fatigue, and jaundice of hepatitis and the puffy eyes of trichinosis and nephritis. Cirrhotic patients frequently have prominent eyes and lid lag, and the alcoholic patient with tremor, prominent eyes, and flushed face may be initially suspected of having thyrotoxicosis. Distinguishing between Graves disease with extreme myopathy and myopathies of other origin can be clinically difficult. The term chronic thyrotoxic myopathy is used to designate a condition characterized by weakness, fatigability, muscular atrophy, and weight loss usually associated with severe thyrotoxicosis. Occasionally fasciculations are seen. The electromyogram result may be abnormal. If the condition is truly of hyperthyroid origin, the thyroid function tests are abnormal and the muscular disorder is reversed when the thyrotoxicosis is relieved. Usually a consideration of the total clinical picture and assessment of TSH and FTI are sufficient to distinguish thyrotoxicosis from polymyositis, myasthenia gravis, or progressive muscular atrophy. True myasthenia gravis may coexist with Graves disease, in which case the myasthenia responds to neostigmine therapy. (The muscle weakness of hyperthyroidism may be slightly improved by neostigmine, but never relieved.) Occasionally electromyograms, muscle biopsy, neostigmine tests, and ACH-receptor antibody assays must be used to settle the problem.

No treatment is ideal and thus indicated in all patients ( 35.1).Three forms of primary therapy for Graves disease are in common use today: (1) destruction of the thyroid by 131-I; (2) blocking of hormone synthesis by antithyroid drugs; and (3) partial or total surgical ablation of the thyroid. Iodine alone as a form of treatment was widely used in the past, but is not used today because its benefits may be transient or incomplete and because more dependable methods became available. Iodine is primarily used now in conjunction with antithyroid drugs to prepare patients for surgical thyroidectomy when that plan of therapy has been chosen. There is, however, some revival of interest in use of iodine treatment as described subsequently. Roentgen irradiation was also used in the past, but is not currently [36]. Suppression of the autoimmune response is being attempted, and currently new treatments blocking the action of Thyroid Stimulating Immunoglobulins are being investigated.

Selection of therapy depends on a multiplicity of considerations [36.1]. Availability of a competent surgeon, for example, undue emotional concern about the hazards of 131-I irradiation, or the probability of adherence to a strict medical regimen might govern ones decision regarding one program of treatment as opposed to another. More than 90% of patients are satistactorly treated cumulating the effects of these treatment.(36.2) Fig. 2

Antithyroid drug therapy offers the opportunity to avoid induced damage to the thyroid (and parathyroids or recurrent nerves), as well as exposure to radiation and operation. In recent studies patients with thyroids under 40 gm weight, with low TRAb levels, and age over 40, were most likely to enter remission (in up to 80%) (36.3, 36.31). The difficulties are the requirement of adhering to a medical schedule for many months or years, frequent visits to the physician, occasional adverse reactions, and, most importantly, a disappointingly low permanent remission rate. Therapy with antithyroid drugs is used as the initial modality in most patients under age 18, in many adults through age 40, and in most pregnant women(36.31). Remission is most likely in young patients, with small thyroids, and mild disease. ATDs may be preferred in elderly patients, those with serious co-morbidities and who have been previously operated upon.

Iodine-131 therapy is quick, easy, moderatly expensive, avoids surgery, and is without significant risk in adults and probably teenagers. The larger doses required to give prompt and certain control generally induce hypothyroidism, and low doses are associated with a frequent requirement for retreatment or ancillary medical management over one to two years. 131-I is used as the primary therapy in most persons over age 40 and in most adults above age 21 if antithyroid drugs fail to control the disease. Treatment of children with 131-I is less common, as discussed later. It can be used in the elderly and those with co-morbidities with precautions.

Surgery, which was the main therapy until 1950, has been to a large extent replaced by 131-I treatment. As the high frequency of 131-I induced hypothyroidism became apparent, some revival of interest in thyroidectomy occurred. The major advantage of surgery is that definitive management is often obtained over an 8- to 12-week period, including preoperative medical control, and many patients are euthyroid after operation. Its well-known disadvantages include expense, surgery itself, and the risks of recurrent nerve and parathyroid damage, hypothyroidism, and recurrence. Nevertheless, if a skillful surgeon is available, surgical management may be used as the primary or secondary therapy in many young adults, as the secondary therapy in children poorly controlled on antithyroid drugs, in pregnant women requiring excessive doses of antithyroid drugs, in patients with significant exophthalmos, and in patients with coincident suspicious thyroid nodules. Early total thyroidectomy has been recommended for treating older, chronically ill patients with thyrotoxic storm if high-dose thionamide treatment, iopanoic acid, and glucocorticoids fail to improve the patients condition within 12 24 hours (36.4).

Two recent surveys reporting trends in therapeutic choices made by thyroidologists have been published [37]. In Europe, most physicians tended to treat children and adults first with antithyroid drugs, and adults secondarily with 131-I or less frequently surgery. Surgery was selected as primary therapy for patients with large goiters. 131-I was selected as the primary treatment in older patients. Most therapists attempted to restore euthyroidism by use of 131-I or surgery. In the United States, 131-I is the initial modality of therapy selected by members of the American Thyroid Association for management of uncomplicated Graves disease in an adult woman [38]. Two-thirds of these clinicians attempt to give 131-I in a dosage calculated to produce euthyroidism, and one-third plan for thyroid ablation.

Introduction-In many thyroid clinics 131-I therapy is now used for most patients with Graves disease who are beyond the adolescent years. It is used in most patients who have had prior thyroid surgery, because the incidence of complications, such as hypoparathyroidism and recurrent nerve palsy, is especially high in this group if a second thyroidectomy is performed. Likewise, it is the therapy of choice for any patient who is a poor risk for surgery because of complicating disease. Surgery may be preferred in patients with significant ophthalmopathy, often combined with prednisone prophylaxis.

Treatment of children-The question of an age limit below which RAI should not be used frequently arises. With lengthening experience these limits have been lowered. Several studies with average follow-up periods of 12 15 years attest to the safety of 131-I therapy in adults [ 39- 41]. In two excellent studies treated persons showed no tendency to develop thyroid cancer, leukemia, or reproductive abnormalities, and their children had no increase in congenital defects or evidence of thyroid damage [ 42- 44]. Franklyn and co workers recently reported on a population based study of 7417 patients treated with 131-I for thyrotoxicosis in England [44.1]. They found an overall decrease in incidence of cancer mortality, but a specific increase in mortality from cancer of the small bowel (7 fold) and of the thyroid (3.25) fold. The absolute risk remains very low, and it is not possible to determine whether the association is related to the basic disease, or to radioiodine treatment. Although there is much less data on long term results in children, there is a increased use of this treatment in teenagers age 15-18, as discussed below. The epidemic of thyroid cancer apparently induced by radioactive iodine isotopes in infants and children living around Chernobyl suggests caution in use of 131-I in younger children. Since the possibility of a general induction of cancer by 131-I is of central concern, it is interesting to calculate the risk in children using the data presented by Rivkees et al (44.2) who are proponents of use of RAI for therapy in young children..The risk of death from any cancer due specifically to radiation exposure is noted by these authors to be 0.16%/rem for children, and the whole body radiation exposure from RAI treatment at age 10 to be 1.45 rem/mCi administered. Rivkees et al advise treatment with doses of RAI greater then 160 uCi/gram thyroid, to achieve a thyroidal radiation dose of at least 150Gy (about 15000 rads). Assuming a reasonable RAIU of 50% and gland size of 40 gm, the administered dose would thus be 40(gm) x 160uCi/gm x 2 (to account for 50% uptake) =12.8 mCi. Thus the long term cancer death risk would be 12.8 (mCi) x 1.45 rem (per mCi) x 0.16% (per rem) = 3%. For a dose of 15mCi the theoretical incremental risk of a later radiation-induced cancer mortality would be 4% at age 5, 2% at age 10, and 1% at age 15. Whether or not accepting a specific 2-4% risk of death from any cancer because of this treatment is of course a matter of judgment by the physician and family. However, this would seem to many persons to constitute a significant risk that might be avoided. We note that this is a thoretical risk, based on known effects of ioniing radiation to induce malignancies, but not so far proven in this setting.

Low 131-I uptake-Certain other findings may dictate the choice of therapy. Occasionally, the 131-I uptake is significantly blocked by prior iodine administration. The effect of iodide dissipates in a few days after stopping exposure, but it may take 3-12 weeks for the effect of amiodarone or IV contrast dyes to be lost. One may either wait for a few days to weeks until another 131-I tracer indicates that the uptake is in a treatable range or use an alternative therapeutic approach such as antithyroid drugs. Coincident nodule(s)-Sometimes a patient with thyrotoxicosis harbors a thyroid gland with a configuration suggesting the presence of a malignant neoplasm. These patients probably should have surgical exploration. While FNA may exclude malignancy, the safety of leaving a highly irradiated nodule in place for many years is not established. Currently few patients who will have RAI therapy are subjected to ultrasonagraphy or scintiscaning. However Stocker et al. found that 12% of Graves patients had cold defects on scan, and among these half were referred for surgery. Six of 22, representing 2% of all Graves patients, 15% of patients with cold nodules, 25% of patients with palpable nodules, and 27% of those going to surgery, had papillary cancer in the location corresponding to the cold defect. Of these patients, one had metastasis to bone and two required multiple treatments with radioiodine. They argue for evaluating patients with a thyroid scintigram and further diagnostic evaluation of cold defects(44.3). Certainly any patient with GD in whom a thyroid nodule is detected, deserves consideration for surgical treatment

Ophthalmopathy-131-I therapy causes an increase in titers of TSH-R Abs, and anti-TG or TPO antibodies, which reflects an activation of autoimmunity. It probably is due to release of thyroid antigens by cell damage, and possibly destruction of intrathyroidal T cells. Many thyroidologists are convinced that 131-I therapy can lead to exacerbation of infiltrative ophthalmopathy, perhaps because of this immunologic response. Tallstedt and associates published data indicating that 131-I therapy causes exacerbation of ophthalmopathy in nearly 25% of patients, while surgery is followed by this response in about half as many.The same group conducted a second randomized trial (44.3) with a follow-up of 4 yr. Patients with a recent diagnosis of Graves hyperthyroidism were randomized to treatment with iodine-131 (163 patients) or 18 months of medical treatment (150 patients). Early substitution with L-T4 was given in both groups.: Worsening or development of eye problems was significantly more common in the iodine-131 treatment group (63 patients; 38.7%) compared with the medical treatment group (32 patients; 21.3%) (P

There are two basically different goals in 131-I dose selection. The traditional approach has been to attempt to give the thyroid 1) sufficient radiation to return the patient to euthyroidism, but not induce hypothyroidism. An alternative approach is to intend to 2) induce hypothyroidism, or euthyroidism and avoid any possible return of hyperthyroidism.

BackgroundThe dosage initially was worked out by a trial-and-error method and by successive approximations. By 1950, the standard dose was 160 uCi 131-I per gram of estimated thyroid weight. Of course, estimating the weight of the thyroid gland by examination of the neck is an inexact procedure, but can now be made more accurate by use of ultrasound. Also, marked variation in radiation sensitivity no doubt exists and cannot be estimated at all. It was gratifying that in practice this dosage scheme worked well enough. In the early 1960s, it was recognized that a complication of RAI therapy was a high incidence of hypothyroidism. This reached 20 40% in the first year after therapy and increased about 2.5% per year, so that by 10 years 50 80% of patients had low function [45,46]. In an effort to reduce the incidence of late hypothyroidism, Hagen and colleagues reduced the quantity of 131-I to 0.08 mCi per gram of estimated gland weight [48]. No increase was reported in the number of patients requiring retreatment, and there was a substantial reduction in the incidence of hypothyroidism. Most of these patients were maintained on potassium iodide for several months after therapy, in order to ameliorate the thyrotoxicosis while the radioiodine had its effect [ 49, 50]. Patients previously treated with 131-I are sensitive to and generally easily controlled by KI. However KI often precipitates hypothyroidism in these patients, which may revert to hyperthyroidism when the KI is discontinued.

Over the years some effort was made to refine the calculation. Account was taken of uptake, half-life of the radioisotope in the thyroid, concentration per gram, and so on, but it is evident that the result in a given instance depends on factors that cannot be estimated precisely [47,]. One factor must be the tendency of the thyroid to return to normal if a dose of radiation is given that is large enough to make the gland approach, for a time, a normal functional state. In many patients, cure is associated with partial or total thyroid ablation. Although we, and many endocrinologists, attempt to scale the dose to the particular patient, some therapists believe it is futile, advocate giving up this attempt, and provide a standard dose giving up to 10000 rads to the thyroid(47.1). Leslie et al reported a comparison of fixed dose treatment and treatment adjusted for 24 hour RAIU, using low or high doses, and found no difference in outcome in either rate of control or induction of hypothyroidism on comparison of the methods. They favor the use of a fixed dose treatment with a single high or low dose (47.2).

Many attempts have been made to improve the therapeutic program by giving the RAI in smaller doses. Reinwein et al [51]. studied 334 patients several years after they had been treated with serial doses of less than 50 uCi 131-I per gram of estimated thyroid weight. One-third of these patients had increased levels of TSH, although they were clinically euthyroid. Only 3% were reported to be clinically hypothyroid.

Dosage adjustmentsmade to induce euthyroidism usually include a factor inc reassing with gland size, a standard dose in microCuries per gram, and a correction to account for 131-I uptake [52]. ALow Dose Protocol was designed to compensate for the apparent radiosensitivity of small glands and resistance of larger glands [53]. Using this approach, after one year, 10% of patients were hypothyroid, 60% are euthyroid, and 30% remained intrinsically toxic [53], although euthyroid by virtue of antithyroid drug treatment. At ten year follow-up, 40% were euthyroid and 60% hypothyroid. A problem with low-dose therapy is that about 25% of patients require a second treatment and 5% require a third. Although this approach reduces early hypothyroidism, it does so at a cost in time, money and patient convenience (Fig. 2). To answer these problems, patients can be re-treated, if need be, within six months, and propranolol and antithyroid drugs can be given between 131-I doses if needed. Unfortunately, experience shows that even low-dose 131-Itherapy is followed by a progressive development of hypothyroidism in up to 40 50% of patients ten years after therapy[ 54- 57].

Thyroid rads, avg.

Impressed by the need to retreat nearly a third of patients, a Moderate Dose Protocol was developed Table -6). This is a fairly conventional program with a mean dose of about 9 mCi. The 131-I dosage is related to gland weight and RAIU, and is increased as gland weight increases. The calculation used is as follows:

uCi given = (estimated thyroid weight in grams) X (uCi/g for appropriate weight from Table 6) / (fractional RAIU at 24 hours) (For readers who may find difficult the conversion of older units in Curies, rads, and rems to newer units of measurement, see Table -7.)

Thyroid rads, avg.

Probably it is wise to do uptakes and treatment using either capsules or liquid isotope for both events. Rini et al have reported that RAIU done with isotope in a capsule appears to give significantly lower values (25 30% lower) than when the isotope is administered in liquid form, and this can significantly influence the determination of the dosage given for therapy(57.1). Berg et al report using a relatively similar protocol (absorbed doses of 100-120 Gy) and that 93% of their patients required replacement therapy after 1-5 years [57.2]. Many studies have presented methods for more accurately delivering a specific radiation dose to the thyroid, and report curing up to 90% of patients, with low incidence of recurrence or hypothyroidism(57.3, 57.4). Franklyn and co-workers analyzed their data on treatment of 813 hyperthyroid patients with radioactive iodide and corroborate many of the previously recognized factors involved in response. Lower dose (in this case 5 mCi), male gender, goiters of medium or large size and severe hyperthyroidism were factors that were associated with failure to cure after one treatment. They suggest using higher fixed initial doses of radioiodine for treating such patients (58.2), as do Leslie et al(58.4). Santos et al (58.4) compared fixed doses of 10 and 15mCi and found no difference in outcome at 12 months post treatment. These authors suggest a standard 10mCi dose, with the larger dose reserved for larger glands.

Planned thyroid partial or complete ablation-All attempts to induce euthyroidism by a calculated moderate dose protocol end up with some patients hypothyroid, and others with persistent hyperthyroidism requiring further treatment. At this time many physicians giving 131-I therapy make no attempt to achieve euthyroidism, and instead use a dose sufficient to largely destroy the thyroid, followed by L- T4 replacement therapy [58]. For example, a dose is given that will result in 7-20 mCi retained at 24 hrs, which is intended to induce hypothyroidism, accepting that in some (or many) patients this will ablate the thyroid completely. A dose of 30 Mci was found to offer a slightly higher cure rate, not surprisingly, at one year than 15 Mci (95 vs 74% (58.1), They argue that this is realistic and preferable since it offers 1) near certainty of prompt control, 2) avoids any chance of persistent or recurrent disease, 3)there is no benefit in having residual thyroid tissue, and 4) hypothyroidism is inevitable in most patients given RAI. Probably many patients given this treatment do in fact have some residual thyroid tissue that is either heavily damaged or reduced in amount so that it can not produce normal amounts of hormone. So far there is no evidence, in adults, that this residual radiated tissue will develop malignant change. There is no certainty at this time that one approach is better than the other. It may be worth remembering that over 50% of patients given calculated moderate dose therapy remain euthyroid after ten years and can easily be surveyed at yearly intervals for hypothyroidism. When giving large doses of 131-I it is prudent to calculate the rads delivered to the gland (as above), which can reach 40-50,000rads. Such large doses of radiation can cause clinically significant radiation thyroiditis, and occasionally damage surrounding structures. And lastly, a speculation. Practitioners comment that the incidence of serious ophthalmopathy seems to be less that in former decades. Prompt diagnosis and therapy might contribute to such a change. Another factor could be the more common ablation of the thyroid during therapy for Graves disease, since this should over time reduce exposure of patients immune system to thyroid antigens.

Lithium with RAI therapy- Although rarely used, RAI combined with lithium is safe and more effective than RAI alone in the cure of hyperthyroidism due to Graves disease, probably because it it causes greater retention of RAI within the thyroid gland.. Bogazzi et al (58.5)reported a study combining lithium with RAI therapy. MMI treatment was withdrawn 5 days prior to treatment, Two hundred ninety-eight patients were treated with RAI plus lithium (900 mg/d for 12 d starting 5 days prior to 131-I treatment) and 353 with RAI alone. RAI dosage was 260mCi/g estimated thyroid weight, corrected for RAIU (done on lithium).. All patients receive prednisone 0.5mg/kg/day, beginning on day 7 after RAI, tapering over 2 months. Patients treated with RAI plus lithium had a higher cure rate (91.0%) than those treated with RAI alone (85.0%, P = 0.030). In addition, patients treated with RAI plus lithium were cured more rapidly (median 60 d) than those treated with RAI alone (median 90 d, P = 0.000). Treatment with lithium inhibited the serum FT4 increase seen after methimazole withdrawal and RAI therapy.

Pretreatment with antithyroid drugsPatients are often treated directly after diagnosis, without prior therapy with antithyroid drugs. This is safe and common in patients with mild hyperthyroidsm and especially those without eye problems. However often physicians give antithyroid drugs before 131-I treatment in order to deplete the gland of stored hormone and to restore the FTI to normal before 131-I therapy. This offers several benefits. The possibility of 131-I induced exacerbation of thyrotoxicosis is reduced, the patient recovers toward normal health, and there is time to reflect on the desired therapy and review any concerns about the use of radioisotope for therapy. If the patient has been on antithyroid drug, it is discontinued two days before RAIU and therapy. Patients can be treated while on antithyroid drug, but this reduces the dose retained, reduces the post-therapy increment in hormone levels, and reduces the cure rate, so seems illogical(58.6) . When antithyroid drugs are discontinued the patients disease may exacerbate, and this must be carefully followed. Beta blockers can be given in this interim, but there is no reason for a prolonged interval between stopping antithyroid drug, and 131-I therapy, unless there is uncertainty about the need for the treatment. Pretreatment with antithyroid drug does not appear in most studies to reduce the efficacy of 131-I treatment. [59] but the debate about the effect of antithyroid drug pretreatment on the efficacy of radioactive iodine therapy continues. In recent studies in which patients were on or off antithyroid therapy, which was discontinued four days, or 1-2 days before treatment, there was no effect on the efficacy of treatment at a one year endpoint (59.1,59.2, 59,3). In another study Bonnema et al found that PTU pretreatment , stopped 4 days prior to 131-I, reduced the efficacy of 131-I(59.6).

Pretreatment is usually optional but is logical in patients with large glands and severe hyperthyroidism. Antithyroid drug therapy does reduce the pretreatment levels of hormone and reduces the rise in thyroid hormone level that may occur after radioactive iodide treatment. This certainly could have a protective effect in individuals who have coincident serious illness such as coronary artery disease, or perhaps individuals who have very large thyroid glands (59.3). It is indicated in two circumstances. In patients with severe heart disease, an 131-I- induced exacerbation of thyrotoxicosis could be serious or fatal. Pretreatment may reduce exacerbation of eye disease (see below), and it does reduce the post-RAI increase in antibody titers(59.1,59.31). The treatment dose of 131-I is best given as soon as possible after the diagnostic RAIU in order to reduce the period in which thyrotoxicosis may exacerbate without treatment, and since any intake of iodine (from diet or medicines or tests) would alter uptake of the treatment dose (59.4), and 2 days seems sufficient.

Post 131-I treatment managementMany patients remain on beta-blockers but require no other treatment after 131-I therapy. Antithyroid drugs can be reinstituted after 5 ( or preferably 7 ) days, with minimal effect on retention of the treatment dose of 131-I.

Alternatively, one may prescribe antithyroid drug (typically 10 mg methimazole q8h) beginning one day after administration of 131-I and add KI (2 drops q8h) after the second dose of methimazole. KI is continued for two weeks, and antithyroid drug as needed. This promotes a rapid return to euthyroidism, but by preventing recirculation of 131-I it can lower the effectiveness of the treatment. This method has been employed in a large number of patients, and is especially useful in patients requiring rapid control- for example, with CHF. A typical response is shown in Fig -3. It also has provided the largest proportion of patients remaining euthyroid at 10 years after therapy, in comparison to other treatment protocols. Glinoer and Verelst also report successful use of this strategy [59.1]. As noted, antithyroid drugs may be given starting 7-10 days after RAI without significantly lowering the radiation dose delivered to the gland.

Treatment using 125-I was tried as an alternative to 131-I, because it might offer certain advantages [60]. 125-I is primarily a gamma ray emitter, but secondary low-energy electrons are produced that penetrate only a few microns, in contrast to the high-energy beta rays of 131-I. Thus, it might theoretically be possible to treat the cytoplasm of the thyroid cell with relatively little damage to the nucleus. Appropriate calculations indicated that the radiation dose to the nucleus could be perhaps one-third that to the cytoplasm, whereas this difference would not exist for 131-I. Extensive therapeutic trials have nonetheless failed to disclose any advantage thus far for 125I. Larger doses 10-20 mCi are required, increasing whole body radiation considerably [ 61, 62].

Doses of 131-I up to 33 mCi can be given to an outpatient basis, and this level is rarely exceeded in treatment of Graves disease. However patients must be given advice (written if possible) on precautions to be followed to prevent unneccessary or excessive exposure of other individuals by radiaactivity administered to the patient. For maximum safety, patients who have received 20 mCi should avoid extended time in public places for 1 day, maximize distance (6 feet) from children and pregnant women for 2 days, may return to work after 1 day, sleep in a separate (6-feet separation) bed from adults for 8 days, sleep in a separate bed from pregnant partners, infant, or child for 20 days, and avoid contact with body fluids (saliva, urine) for at least one week. Lower therapeutic doses require proportionally more moderate precautions. The basic NRC rule is that patients may be released from hospital when (1) the 131I measured dose rate is 7mrem/hr at 1m, or (2) when the expected total dose another person would receive is unlikely to exceed 500mrem (5mSv). Written precaution instructions are required If 100mrem (1mSv) may be exceeded in any person. This topic is well covered in articles by Sisson et al ( andLiu et al (62.1).

If adequate treatment has been given, the T4 level falls progressively, beginning in one to three weeks.. Labeled thyroid hormones, iodotyrosines, and iodoproteins appear in the circulation [63,63.1]. TG is released, starting immediately after therapy. Another iodoprotein, which seems to be an iodinated albumin, is also found in plasma. This compound is similar or identical to a quantitatively insignificant secretion product of the normal gland. It comprises up to 15% or more of the circulating serum 131-I in thyrotoxic patients [64]. It is heavily labeled after 131-I therapy, and its proportional secretion is probably increased by the radiation. Iodotyrosine present in the serum may represent leakage from the thyroid gland, or may be derived from peripheral metabolism of TG or iodoalbumin released from the thyroid.

The return to the euthyroid state usually requires at least two months, and often the declining function of the gland proceeds gradually over six months to a year. For this reason, it is logical to avoid retreating a patient before six months have elapsed unless there is no evidence of control of the disease. While awaiting the response to131-I the symptoms may be controlled by propranolol, antithyroid drugs, or iodide. Hypothyroidism develops transiently in 10 20% of patients, but thyroid function returns to normal in most of these patients in a period ranging from three to six months. These patients rarely become toxic again. Others develop permanent hypothyroidism and require replacement therapy. It is advantageous to give the thyroid adequate time to recover function spontaneously before starting permanent replacement therapy. This can be difficult for the patient unless partial T4 replacement is given. Unfortunately, one of the common side effects of treating hyperthyroidism is weight gain, averaging about 20 lbs through four years after treatment (64.1).

Patients may develop transient increases in FTI and T3 at 2-4 months after treatment [63.1], sometimes associated with enlargement of the thyroid. This may represent an inflammatory or immune response to the irradiationinduced thyroid damage, and the course may change rapidly with a dramatic drop to hypothyroidism in the 4-5th month.

Hypothyroidism may ultimately be inescapable after any amount of radiation that is sufficient to reduce the function of the hyperplastic thyroid to normal [65]. Many apparently euthyroid patients (as many as half) have elevated serum levels of TSH long after 131-I therapy, with normal plasma hormone levels [66]. An elevated TSH level with a low normal T4level is an indicator of changes progressing toward hypothyroidism [67]. The hypothyroidism is doubtless also related to the continued autoimmune attack on thyroid cells. Hypofunction is a common end stage of Graves disease independent of 131-I use; it occurs spontaneously as first noted in 1895(!) [68] and in patients treated only with antithyroid drugs [69]. Just as after surgery, the development of hypothyroidism is correlated positively with the presence of antithyroid antibodies.

During the rapid development of postradiation hypothyroidism, the typical symptoms of depressed metabolism are evident, but two rather unusual features also occur. The patients may have marked aching and stiffness of joints and muscles. They may also develop severe centrally located and persistent headache. The headache responds rapidly to thyroid hormone therapy. Hair loss can also be dramatic at this time.

In patients developing hypothyroidism rapidly, the plasma T4 level and FTI accurately reflect the metabolic state. However, it should be noted that the TSH response may be suppressed for weeks or months by prior thyrotoxicosis; thus, the TSH level may not accurately reflect hypothyroidism in these persons and should not be used in preference to the FTI or FT4.

If permanent hypothyroidism develops, the patient is given replacement hormone therapy and is impressed with the necessity of taking the medication for the remainder of his or her life. Thyroid hormone replacement is not obligatory for those who develop only temporary hypothyroidism, although it is possible that patients in this group should receive replacement hormone, for their glands have been severely damaged and they are likely to develop hypothyroidism at a later date. Perhaps these thyroids, under prolonged TSH stimulation, may tend to develop adenomatous or malignant changes, but this has not been observed. Many middle-aged women gain weight excessively after radioactive iodide treatment of hyperthyroidism. Usually such patients are on what is presumed to be appropriate T4 replacement therapy. Tigas et al note that such weight gain is less common after ablative therapy for thyroid cancer, in which case larger doses of thyroxine are generally prescribed. Thus they question whether the excessive weight gain after radioactive iodide treatment of Graves disease is due to the fact that insufficient thyroid hormone is being provided, even though TSH is within the normal range. They suggest that restoration of serum TSH to the reference range by T4 alone may not constitute adequate hormone replacement [ 69a}. We noted above that the correct reference range for TT4 and FT4, when the patient is on replacement T4, should be 20% higher than normal.

Permanent replacement therapy (regardless of the degree of thyroid destruction) for children who receive 131-I has a better theoretical basis. In these cases, it is advisable to prevent TSH stimulation of the thyroid and so mitigate any possible tendency toward carcinoma formation.

Exacerbation of thyrotoxicosis-During the period immediately after therapy, there may be a transient elevation of the T4 or T3 level [70], but usually the T4 level falls progressively toward normal. Among treated hyperthyroid patients with Graves disease, only rare exacerbations of the disease are seen. These patients may have cardiac problems such as worsening angina pectoris, congestive heart failure, or disturbances of rhythm such as atrial fibrillation or even ventricular tachycardia. Radiation-induced thyroid storm and even death have unfortunately been reported [71- 73]. These untoward events argue for pretreatment of selected patients who have other serious illness, especially cardiac disease, with antithyroid drugs prior to 131-I therapy.

The immediate side effects of 131-I therapy are typically minimal. As noted above, transient exacerbation of thyrotoxicosis can occur, and apparent thyroid storm has been induced within a day (or days) after 131-I therapy. A few patients develop mild pain and tenderness over the thyroid and, rarely, dysphagia. Some patients develop temporary hair loss, but this condition occurs two to three months after therapy rather than at two to three weeks, as occurs after ordinary radiation epilation. Hair loss also occurs after surgical therapy, so that it is a metabolic rather than a radiation effect. If the loss of hair is due to the change in metabolic status, it generally recovers in a few weeks or months. However hair thinning, patchy alopecia, and total alopecia, are all associated with Graves Disease, probably as another auto-immune processes. In this situation the prognosis for recovery is less certain, and occasionally some other therapy for the hair loss (such as steroids) is indicated. Permanent hypoparathyroidism has been reported very rarely as a complication of RAI therapy for heart disease and thyrotoxicosis[ 74- 76]. Patients treated for hyperthyroidism with 131-I received approximately 39 microGy/MBq administered (about 0.144rad/mCi) of combined beta and gamma radiation to the testes. This is reported to cause no significant changes in FSH. Nevertheless, testosterone declines transiently for several months, but there is no variation in sperm motility or % abnormal forms (76.1). Long term studies of patients after RAI treatment by Franklyn et al (76.2) show a slight increase in mortality which appears to be related to cardiovascular disease, possibly related to periods of hypothyroidism.

Worsening of ophthalmopathy after RAIIn contrast to the experience with antithyroid drugs or surgery, antithyroid antibodies including TSAb levels increase after RAI [ 77, 78]. (Fig. 11-4, above). Coincident with this condition, exophthalmos may be worsened [79].(Fig. 11-5, below). This change is most likely an immunologic reaction to discharged thyroid antigens.The relationship of radiation therapy to exacerbation of exophthalmos has beem questioned], but much recent data indicates that there is a definite correlation[ 79, 80, 80.1, 80.2, 80.3]. Many therapists consider bad eyes to be a relative contraindication to RAI. Induction of hypothyroidism, with elevation of TSH, may contribute to worsening of ophthalmopathy. This offers support for early induction of T4 replacement (80.3). Pretreatment with antithyroid drugs has been used empirically in an attempt to prevent this complication. Its benefit, if any, may be related to an immunosuppressive effect of PTU, described below. Treatment with methimazole before and for three months after I-131 therapy has been shown to help prevent the treatment-induced rise in TSH-R antibodies which is otherwise seen[81].

Prophylaxis with prednisone after 131-I helps prevent exacerbation of exophthalmos, and this approach is now the standard approach in patients who have significant exophthalmos at the time of treatment [ 82, 82.1]. (Fig. 6, below) The recommended dose is 30 mg/day for one month, tapering then over 2-3 months. Of course prednisone or other measures can be instituted at the time of any worsening of ophthalmopathy. In this instance doses of 30-60 mg/day are employed, and usually are required over several months. While treatment with prednisone helps prevent eye problems, it does not appear to reduce the effectiveness of RAI in controlling the hyperthyroidism(82.2). Thyroidectomy, with total removal of the gland, should be considered for patients with serious active eye disease. Operative removal of the thyroid is followed by gradual diminution is TSH-R antibodies.(82.3 ), and as shown by Tallstedt is associated with a lower incidence of worsening eye problems than is initial RAI treatment. Several studies document better outcomes of ophthalmopathy in patients with GD who have total thyroidectomy vs those treated by other means(82.4, 82.5, 82.6).

Failure of 131-I to cure thyrotoxicosis occurs occasionally even after 2 or 3 treatments, and rarely 4 or 5 therapies are given. The reason for this failure is usually not clear. The radiation effect may occur slowly. A large store of hormone in a large gland may be one cause of a slow response. Occasional glands having an extremely rapid turnover of 131-I requiring such high doses of the isotope that surgery is preferable to continued 131-I therapy and its attendant whole body radiation. If a patient fails to respond to one or two doses of 131-I, it is important to consider that rapid turnover may reduce the effective radiation dose. Turnover can easily be estimated by measuring RAIU at 4, 12, 24, and 48 hours, or longer. The usual combined physical and biological half-time of 131-I retention is about 6 days. This may be reduced to 1 or 2 days in some cases, especially in patients who have had prior therapy or subtotal thyroidectomy. If this rapid release of 131-I is found, and 131-I therapy is desired, the total dose given must be increased to compensate for rapid release. A rough guide to this increment is as follows:

Increased dose = usual dose X ( (usual half time of 6 days) / (observed half time of X days) )

Most successfully treated glands return to a normal or cosmetically satisfactory size. Some large glands remain large, and in that sense may constitute a treatment failure. In such a situation secondary thyroidectomy could be done, but it is rarely required in practice.

Long term care- Patients who have been treated with RAI should continue under the care of a physician who is interested in their thyroid problem for the remainder of their lives. The first follow-up visit should be made six to eight weeks after therapy. By this time, it will often be found that the patient has already experienced considerable improvement and has begun to gain weight. The frequency of subsequent visits will depend on the progress of the patient. Symptoms of hypothyroidism, if they develop, are usually not encountered until after two to four months, but one of the unfortunate facts of RAI therapy is that hypothyroidism may occur almost any time after the initial response.

In the early days of RAI treatment for Graves disease, only patients over 45 years of age were selected for treatment because of the fear of ill effects of radiation. This age limit was gradually lowered, and some clinics, after experience extending over nearly 40 years, have now abandoned most age limitation. The major fear has been concern for induction of neoplasia, as well as the possibility that 131-I might induce undesirable mutations in the germ cells that would appear in later generations.

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Thyroid Disease Manager : Diagnosis and Treatment of Graves

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National Human Genome Research Institute

NHGRI-ASHG fellowships fulfill critical need in science policy and education

For several years, NHGRI and the American Society of Human Genetics (ASHG) have provided a pathway for scientists who want to pursue careers in science policy or education. The Genetics and Public Policy Fellowship and the Genetics and Education Fellowship offer effective experiences in the public, private and non-profit arenas to those with graduate education in genetics. These fellowships help build the skills required to inform science policy and education. Our 2016-2017 fellows share what they’ve accomplished.

Geared to students grade 9-12 worldwide, the American Society of Human Genetics (ASHG) DNA Day Essay Contest celebrates National DNA Day by asking students to examine, question and reflect on important concepts in genetics. This year’s question asks students to describe a disease or condition researchers are attempting to treat and how gene therapy might repair the underlying cause of the disease or condition. Deadline: March 10, 2017, at 5 p.m. U.S. Eastern Time. See: DNA Day Essay Contest

Your family health history can identify whether you are at a higher risk for some diseases. But people don’t necessarily know their entire family’s health history. A new study shows that asking multiple family members for family health histories can improve the accuracy of both the family’s health history and personalized risk assessments. NHGRI intramural researchers published the study in the American Journal of Preventive Medicine on January 4, 2016.

On June 5-7, 2017, the conference Genomics and Society: Expanding the ELSI Universe will gather ethical, legal and social implications researchers to reflect on current research and discuss future directions. With keynote speakers, plenary panels, workshops, and a wide range of paper, panel, and poster presentations, the Congress will provide an opportunity for scholars to reflect on current research and envision future directions for ELSI research. For more information and to register:

Through a simple blood test, physicians will soon be able to map the fetus’ entire collection of genes (the whole genome) using fetal DNA that floats in the mother’s blood. But a survey of 1,000 physicians says that ethical guidelines must be developed first. Researchers with the National Human Genome Research Institute published their findings in the December 6th issue of the journal Prenatal Diagnosis.

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National Human Genome Research Institute

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Steroid – Wikipedia

This article is about the family of polycyclic chemical compounds. For the drugs, also used as performance-enhancing substances, see Anabolic steroid. For the scientific journal, see Steroids (journal).

A steroid is an organic compound with four rings arranged in a specific configuration. Examples include the dietary lipid cholesterol, the sex hormones estradiol and testosterone[2]:1019 and the anti-inflammatory drug dexamethasone.[3] Steroids have two principal biological functions: certain steroids (such as cholesterol) are important components of cell membranes which alter membrane fluidity, and many steroids are signaling molecules which activate steroid hormone receptors.

The steroid core structure is composed of seventeen carbon atoms, bonded in four “fused” rings: three six-member cyclohexane rings (rings A, B and C in the first illustration) and one five-member cyclopentane ring (the D ring). Steroids vary by the functional groups attached to this four-ring core and by the oxidation state of the rings. Sterols are forms of steroids with a hydroxyl group at position three and a skeleton derived from cholestane.[1]:1785f[4] They can also vary more markedly by changes to the ring structure (for example, ring scissions which produce secosteroids such as vitamin D3).

Hundreds of steroids are found in plants, animals and fungi. All steroids are manufactured in cells from the sterols lanosterol (animals and fungi) or cycloartenol (plants). Lanosterol and cycloartenol are derived from the cyclization of the triterpene squalene.[5]

Space-filling representation

Ball-and-stick representation

Gonane, also known as steran or cyclopentaperhydrophenanthrene, the simplest steroid and the nucleus of all steroids and sterols,[6][7] is composed of seventeen carbon atoms in carbon-carbon bonds forming four fused rings in a three-dimensional shape. The three cyclohexane rings (A, B, and C in the first illustration) form the skeleton of a perhydro derivative of phenanthrene. The D ring has a cyclopentane structure. When the two methyl groups and eight carbon side chains (at C-17, as shown for cholesterol) are present, the steroid is said to have a cholestane framework. The two common 5 and 5 stereoisomeric forms of steroids exist because of differences in the side of the largely planar ring system where the hydrogen (H) atom at carbon-5 is attached, which results in a change in steroid A-ring conformation.

Examples of steroid structures are:

In addition to the ring scissions (cleavages), expansions and contractions (cleavage and reclosing to a larger or smaller rings)all variations in the carbon-carbon bond frameworksteroids can also vary:

For instance, sterols such as cholesterol and lanosterol have an hydroxyl group attached at position C-3, while testosterone and progesterone have a carbonyl (oxo substituent) at C-3; of these, lanosterol alone has two methyl groups at C-4 and cholesterol (with a C-5 to C-6 double bond) differs from testosterone and progesterone (which have a C-4 to C-5 double bond).

The following are some common categories of steroids. In eukaryotes, steroids are found in fungi, animals, and plants. Fungal steroids include the ergosterols.

Animal steroids include compounds of vertebrate and insect origin, the latter including ecdysteroids such as ecdysterone (controlling molting in some species). Vertebrate examples include the steroid hormones and cholesterol; the latter is a structural component of cell membranes which helps determine the fluidity of cell membranes and is a principal constituent of plaque (implicated in atherosclerosis). Steroid hormones include:

Plant steroids include steroidal alkaloids found in Solanaceae,[8] the phytosterols, and the brassinosteroids (which include several plant hormones). In prokaryotes, biosynthetic pathways exist for the tetracyclic steroid framework (e.g. in mycobacteria)[9] where its origin from eukaryotes is conjectured[10] and the more-common pentacyclic triterpinoid hopanoid framework.[11]

Steroids can be classified based on their chemical composition.[12] One example of how MeSH performs this classification is available at the Wikipedia MeSH catalog. Examples of this classification include:

The gonane (steroid nucleus) is the parent 17-carbon tetracyclic hydrocarbon molecule with no alkyl sidechains.[13]

Secosteroids (Latin seco, “to cut”) are a subclass of steroidal compounds resulting, biosynthetically or conceptually, from scission (cleavage) of parent steroid rings (generally one of the four). Major secosteroid subclasses are defined by the steroid carbon atoms where this scission has taken place. For instance, the prototypical secosteroid cholecalciferol, vitamin D3 (shown), is in the 9,10-secosteroid subclass and derives from the cleavage of carbon atoms C-9 and C-10 of the steroid B-ring; 5,6-secosteroids and 13,14-steroids are similar.[14]

Norsteroids (nor-, L. norma; “normal” in chemistry, indicating carbon removal)[15] and homosteroids (homo-, Greek homos; “same”, indicating carbon addition) are structural subclasses of steroids formed from biosynthetic steps. The former involves enzymic ring expansion-contraction reactions, and the latter is accomplished (biomimetically) or (more frequently) through ring closures of acyclic precursors with more (or fewer) ring atoms than the parent steroid framework.[16]

Combinations of these ring alterations are known in nature. For instance, ewes who graze on corn lily ingest cyclopamine (shown) and veratramine, two of a sub-family of steroids where the C- and D-rings are contracted and expanded respectively via a biosynthetic migration of the original C-13 atom. Ingestion of these C-nor-D-homosteroids results in birth defects in lambs: cyclopia from cyclopamine and leg deformity from veratramine.[17] A further C-nor-D-homosteroid (nakiterpiosin) is excreted by Okinawan cyanobacteriosponges Terpios hoshinota leading to coral mortality from black coral disease.[18] Nakiterpiosin-type steroids are active against the signaling pathway involving the smoothened and hedgehog proteins, a pathway which is hyperactive in a number of cancers.

Steroids and their metabolites often function as signalling molecules (the most notable examples are steroid hormones), and steroids and phospholipids are components of cell membranes. Steroids such as cholesterol decrease membrane fluidity.[19] Similar to lipids, steroids are highly concentrated energy stores. However, they are not typically sources of energy; in mammals, they are normally metabolized and excreted.

Steroids play critical roles in a number of disorders, including malignancies like Prostate Cancer, where steroid production inside and outside the tumour promotes cancer cell aggressiveness.[20]

Two classes of drugs target the mevalonate pathway: statins (used to reduce elevated cholesterol levels) and bisphosphonates (used to treat a number of bone-degenerative diseases).

The hundreds of steroids found in animals, fungi, and plants are made from lanosterol (in animals and fungi; see examples above) or cycloartenol (in plants). Lanosterol and cycloartenol derive from cyclization of the triterpenoid squalene.[5]

Steroid biosynthesis is an anabolic pathway which produces steroids from simple precursors. A unique biosynthetic pathway is followed in animals (compared to many other organisms), making the pathway a common target for antibiotics and other anti-infection drugs. Steroid metabolism in humans is also the target of cholesterol-lowering drugs, such as statins.

In humans and other animals the biosynthesis of steroids follows the mevalonate pathway, which uses acetyl-CoA as building blocks for dimethylallyl pyrophosphate (DMAPP) and isopentenyl pyrophosphate (IPP).[21][bettersourceneeded] In subsequent steps DMAPP and IPP join to form geranyl pyrophosphate (GPP), which synthesizes the steroid lanosterol. Modifications of lanosterol into other steroids are classified as steroidogenesis transformations.

The mevalonate pathway (also called HMG-CoA reductase pathway) begins with acetyl-CoA and ends with dimethylallyl pyrophosphate (DMAPP) and isopentenyl pyrophosphate (IPP).

DMAPP and IPP donate isoprene units, which are assembled and modified to form terpenes and isoprenoids[22] (a large class of lipids, which include the carotenoids and form the largest class of plant natural products.[23] Here, the isoprene units are joined to make squalene and folded into a set of rings to make lanosterol.[24]

Lanosterol can then be converted into other steroids, such as cholesterol and ergosterol.[24][25]

Steroidogenesis is the biological process by which steroids are generated from cholesterol and changed into other steroids.[27] The pathways of steroidogenesis differ among species. The major classes of steroid hormones, with prominent members and examples of related functions, are:

Human steroidogenesis occurs in a number of locations:

In plants and bacteria, the non-mevalonate pathway uses pyruvate and glyceraldehyde 3-phosphate as substrates.[22][30]

During diseases pathways otherwise not significant in healthy humans can become utilized. For example, in one form of congenital adrenal hyperplasia an deficiency in the 21-hydroxylase enzymatic pathway leads to an excess of 17-Hydroxyprogesterone (17-OHP) this pathological excess of 17-OHP in turn may be converted to dihydrotestosterone (DHT, a potent androgen) through among others 17,20 Lyase (a member of the cytochrome P450 family of enzymes), 5-Reductase and 3-Hydroxysteroid dehydrogenase.[31]

Steroids are primarily oxidized by cytochrome P450 oxidase enzymes, such as CYP3A4. These reactions introduce oxygen into the steroid ring, allowing the cholesterol to be broken up by other enzymes into bile acids.[32] These acids can then be eliminated by secretion from the liver in bile.[33] The expression of the oxidase gene can be upregulated by the steroid sensor PXR when there is a high blood concentration of steroids.[34] Steroid hormones, lacking the side chain of cholesterol and bile acids, are typically hydroxylated at various ring positions or oxidized at the 17 position, conjugated with sulfate or glucuronic acid and excreted in the urine.[35]

Steroid isolation, depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more[36] or the isolation of “analytical quantities” of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram.[37][pageneeded] The methods of isolation to achieve the two scales of product are distinct, but include extraction, precipitation, adsorption, chromatography, and crystallization. In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS, are chosen to be “orthogonal”achieving their separations based on distinct modes of interaction between substance and isolating matrixto detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography.[2]:1019Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity.[37]

Microbial catabolism of phytosterol side chains yields C-19 steroids, C-22 steroids, and 17-ketosteroids (i.e. precursors to adrenocortical hormones and contraceptives).[38][39][40][41] The addition and modification of functional groups is key when producing the wide variety of medications available within this chemical classification. These modifications are performed using conventional organic synthesis and/or biotransformation techniques.[42][43]

The semisynthesis of steroids often begins from precursors such as cholesterol,[41]phytosterols,[40] or sapogenins.[44] The efforts of Syntex, a company involved in the Mexican barbasco trade, used Dioscorea mexicana to produce the sapogenin diosgenin in the early days of the synthetic steroid pharmaceutical industry.[36]

Some steroidal hormones are economically obtained only by total synthesis from petrochemicals (e.g. 13-alkyl steroids).[41] For example, the pharmaceutical Norgestrel begins from Methoxy-1-tetralone, a petrochemical derived from phenol.

A number of Nobel Prizes have been awarded for steroid research, including:

Steroid signaling



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Steroid – Wikipedia

Recommendation and review posted by Bethany Smith

Medicine – Wikipedia

Medicine (British English i; American English i) is the science and practice of the diagnosis, treatment, and prevention of disease.[1][2] The word medicine is derived from Latin medicus, meaning “a physician”.[3][4] Medicine encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness. Contemporary medicine applies biomedical sciences, biomedical research, genetics, and medical technology to diagnose, treat, and prevent injury and disease, typically through pharmaceuticals or surgery, but also through therapies as diverse as psychotherapy, external splints and traction, medical devices, biologics, and ionizing radiation, amongst others.[5]

Medicine has existed for thousands of years, during most of which it was an art (an area of skill and knowledge) frequently having connections to the religious and philosophical beliefs of local culture. For example, a medicine man would apply herbs and say prayers for healing, or an ancient philosopher and physician would apply bloodletting according to the theories of humorism. In recent centuries, since the advent of modern science, most medicine has become a combination of art and science (both basic and applied, under the umbrella of medical science). While stitching technique for sutures is an art learned through practice, the knowledge of what happens at the cellular and molecular level in the tissues being stitched arises through science.

Prescientific forms of medicine are now known as traditional medicine and folk medicine. They remain commonly used with or instead of scientific medicine and are thus called alternative medicine. For example, evidence on the effectiveness of acupuncture is “variable and inconsistent” for any condition,[6] but is generally safe when done by an appropriately trained practitioner.[7] In contrast, treatments outside the bounds of safety and efficacy are termed quackery.

Medical availability and clinical practice varies across the world due to regional differences in culture and technology. Modern scientific medicine is highly developed in the Western world, while in developing countries such as parts of Africa or Asia, the population may rely more heavily on traditional medicine with limited evidence and efficacy and no required formal training for practitioners.[8] Even in the developed world however, evidence-based medicine is not universally used in clinical practice; for example, a 2007 survey of literature reviews found that about 49% of the interventions lacked sufficient evidence to support either benefit or harm.[9]

In modern clinical practice, doctors personally assess patients in order to diagnose, treat, and prevent disease using clinical judgment. The doctor-patient relationship typically begins an interaction with an examination of the patient’s medical history and medical record, followed by a medical interview[10] and a physical examination. Basic diagnostic medical devices (e.g. stethoscope, tongue depressor) are typically used. After examination for signs and interviewing for symptoms, the doctor may order medical tests (e.g. blood tests), take a biopsy, or prescribe pharmaceutical drugs or other therapies. Differential diagnosis methods help to rule out conditions based on the information provided. During the encounter, properly informing the patient of all relevant facts is an important part of the relationship and the development of trust. The medical encounter is then documented in the medical record, which is a legal document in many jurisdictions.[11] Follow-ups may be shorter but follow the same general procedure, and specialists follow a similar process. The diagnosis and treatment may take only a few minutes or a few weeks depending upon the complexity of the issue.

The components of the medical interview[10] and encounter are:

The physical examination is the examination of the patient for medical signs of disease, which are objective and observable, in contrast to symptoms which are volunteered by the patient and not necessarily objectively observable.[12] The healthcare provider uses the senses of sight, hearing, touch, and sometimes smell (e.g., in infection, uremia, diabetic ketoacidosis). Four actions are the basis of physical examination: inspection, palpation (feel), percussion (tap to determine resonance characteristics), and auscultation (listen), generally in that order although auscultation occurs prior to percussion and palpation for abdominal assessments.[13]

The clinical examination involves the study of:

It is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above.

The treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a specialist, or watchful observation. Follow-up may be advised. Depending upon the health insurance plan and the managed care system, various forms of “utilization review”, such as prior authorization of tests, may place barriers on accessing expensive services.[14]

The medical decision-making (MDM) process involves analysis and synthesis of all the above data to come up with a list of possible diagnoses (the differential diagnoses), along with an idea of what needs to be done to obtain a definitive diagnosis that would explain the patient’s problem.

On subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, and lab or imaging results or specialist consultations.

Contemporary medicine is in general conducted within health care systems. Legal, credentialing and financing frameworks are established by individual governments, augmented on occasion by international organizations, such as churches. The characteristics of any given health care system have significant impact on the way medical care is provided.

From ancient times, Christian emphasis on practical charity gave rise to the development of systematic nursing and hospitals and the Catholic Church today remains the largest non-government provider of medical services in the world.[15] Advanced industrial countries (with the exception of the United States)[16][17] and many developing countries provide medical services through a system of universal health care that aims to guarantee care for all through a single-payer health care system, or compulsory private or co-operative health insurance. This is intended to ensure that the entire population has access to medical care on the basis of need rather than ability to pay. Delivery may be via private medical practices or by state-owned hospitals and clinics, or by charities, most commonly by a combination of all three.

Most tribal societies provide no guarantee of healthcare for the population as a whole. In such societies, healthcare is available to those that can afford to pay for it or have self-insured it (either directly or as part of an employment contract) or who may be covered by care financed by the government or tribe directly.

Transparency of information is another factor defining a delivery system. Access to information on conditions, treatments, quality, and pricing greatly affects the choice by patients/consumers and, therefore, the incentives of medical professionals. While the US healthcare system has come under fire for lack of openness,[18] new legislation may encourage greater openness. There is a perceived tension between the need for transparency on the one hand and such issues as patient confidentiality and the possible exploitation of information for commercial gain on the other.

Provision of medical care is classified into primary, secondary, and tertiary care categories.

Primary care medical services are provided by physicians, physician assistants, nurse practitioners, or other health professionals who have first contact with a patient seeking medical treatment or care. These occur in physician offices, clinics, nursing homes, schools, home visits, and other places close to patients. About 90% of medical visits can be treated by the primary care provider. These include treatment of acute and chronic illnesses, preventive care and health education for all ages and both sexes.

Secondary care medical services are provided by medical specialists in their offices or clinics or at local community hospitals for a patient referred by a primary care provider who first diagnosed or treated the patient. Referrals are made for those patients who required the expertise or procedures performed by specialists. These include both ambulatory care and inpatient services, emergency rooms, intensive care medicine, surgery services, physical therapy, labor and delivery, endoscopy units, diagnostic laboratory and medical imaging services, hospice centers, etc. Some primary care providers may also take care of hospitalized patients and deliver babies in a secondary care setting.

Tertiary care medical services are provided by specialist hospitals or regional centers equipped with diagnostic and treatment facilities not generally available at local hospitals. These include trauma centers, burn treatment centers, advanced neonatology unit services, organ transplants, high-risk pregnancy, radiation oncology, etc.

Modern medical care also depends on information still delivered in many health care settings on paper records, but increasingly nowadays by electronic means.

In low-income countries, modern healthcare is often too expensive for the average person. International healthcare policy researchers have advocated that “user fees” be removed in these areas to ensure access, although even after removal, significant costs and barriers remain.[19]

Working together as an interdisciplinary team, many highly trained health professionals besides medical practitioners are involved in the delivery of modern health care. Examples include: nurses, emergency medical technicians and paramedics, laboratory scientists, pharmacists, podiatrists, physiotherapists, respiratory therapists, speech therapists, occupational therapists, radiographers, dietitians, and bioengineers, surgeons, surgeon’s assistant, surgical technologist.

The scope and sciences underpinning human medicine overlap many other fields. Dentistry, while considered by some a separate discipline from medicine, is a medical field.

A patient admitted to the hospital is usually under the care of a specific team based on their main presenting problem, e.g., the Cardiology team, who then may interact with other specialties, e.g., surgical, radiology, to help diagnose or treat the main problem or any subsequent complications/developments.

Physicians have many specializations and subspecializations into certain branches of medicine, which are listed below. There are variations from country to country regarding which specialties certain subspecialties are in.

The main branches of medicine are:

In the broadest meaning of “medicine”, there are many different specialties. In the UK, most specialities have their own body or college, which have its own entrance examination. These are collectively known as the Royal Colleges, although not all currently use the term “Royal”. The development of a speciality is often driven by new technology (such as the development of effective anaesthetics) or ways of working (such as emergency departments); the new specialty leads to the formation of a unifying body of doctors and the prestige of administering their own examination.

Within medical circles, specialities usually fit into one of two broad categories: “Medicine” and “Surgery.” “Medicine” refers to the practice of non-operative medicine, and most of its subspecialties require preliminary training in Internal Medicine. In the UK, this was traditionally evidenced by passing the examination for the Membership of the Royal College of Physicians (MRCP) or the equivalent college in Scotland or Ireland. “Surgery” refers to the practice of operative medicine, and most subspecialties in this area require preliminary training in General Surgery, which in the UK leads to membership of the Royal College of Surgeons of England (MRCS). At present, some specialties of medicine do not fit easily into either of these categories, such as radiology, pathology, or anesthesia. Most of these have branched from one or other of the two camps above; for example anaesthesia developed first as a faculty of the Royal College of Surgeons (for which MRCS/FRCS would have been required) before becoming the Royal College of Anaesthetists and membership of the college is attained by sitting for the examination of the Fellowship of the Royal College of Anesthetists (FRCA).

Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, to help improve bodily function or appearance or to repair unwanted ruptured areas (for example, a perforated ear drum). Surgeons must also manage pre-operative, post-operative, and potential surgical candidates on the hospital wards. Surgery has many sub-specialties, including general surgery, ophthalmic surgery, cardiovascular surgery, colorectal surgery, neurosurgery, oral and maxillofacial surgery, oncologic surgery, orthopedic surgery, otolaryngology, plastic surgery, podiatric surgery, transplant surgery, trauma surgery, urology, vascular surgery, and pediatric surgery. In some centers, anesthesiology is part of the division of surgery (for historical and logistical reasons), although it is not a surgical discipline. Other medical specialties may employ surgical procedures, such as ophthalmology and dermatology, but are not considered surgical sub-specialties per se.

Surgical training in the U.S. requires a minimum of five years of residency after medical school. Sub-specialties of surgery often require seven or more years. In addition, fellowships can last an additional one to three years. Because post-residency fellowships can be competitive, many trainees devote two additional years to research. Thus in some cases surgical training will not finish until more than a decade after medical school. Furthermore, surgical training can be very difficult and time-consuming.

Internal medicine is the medical specialty dealing with the prevention, diagnosis, and treatment of adult diseases. According to some sources, an emphasis on internal structures is implied.[20] In North America, specialists in internal medicine are commonly called “internists.” Elsewhere, especially in Commonwealth nations, such specialists are often called physicians.[21] These terms, internist or physician (in the narrow sense, common outside North America), generally exclude practitioners of gynecology and obstetrics, pathology, psychiatry, and especially surgery and its subspecialities.

Because their patients are often seriously ill or require complex investigations, internists do much of their work in hospitals. Formerly, many internists were not subspecialized; such general physicians would see any complex nonsurgical problem; this style of practice has become much less common. In modern urban practice, most internists are subspecialists: that is, they generally limit their medical practice to problems of one organ system or to one particular area of medical knowledge. For example, gastroenterologists and nephrologists specialize respectively in diseases of the gut and the kidneys.[22]

In the Commonwealth of Nations and some other countries, specialist pediatricians and geriatricians are also described as specialist physicians (or internists) who have subspecialized by age of patient rather than by organ system. Elsewhere, especially in North America, general pediatrics is often a form of Primary care.

There are many subspecialities (or subdisciplines) of internal medicine:

Training in internal medicine (as opposed to surgical training), varies considerably across the world: see the articles on Medical education and Physician for more details. In North America, it requires at least three years of residency training after medical school, which can then be followed by a one- to three-year fellowship in the subspecialties listed above. In general, resident work hours in medicine are less than those in surgery, averaging about 60 hours per week in the USA. This difference does not apply in the UK where all doctors are now required by law to work less than 48 hours per week on average.

The followings are some major medical specialties that do not directly fit into any of the above-mentioned groups.

Some interdisciplinary sub-specialties of medicine include:

Medical education and training varies around the world. It typically involves entry level education at a university medical school, followed by a period of supervised practice or internship, and/or residency. This can be followed by postgraduate vocational training. A variety of teaching methods have been employed in medical education, still itself a focus of active research. In Canada and the United States of America, a Doctor of Medicine degree, often abbreviated M.D., or a Doctor of Osteopathic Medicine degree, often abbreviated as D.O. and unique to the United States, must be completed in and delivered from a recognized university.

Since knowledge, techniques, and medical technology continue to evolve at a rapid rate, many regulatory authorities require continuing medical education. Medical practitioners upgrade their knowledge in various ways, including medical journals, seminars, conferences, and online programs.

In most countries, it is a legal requirement for a medical doctor to be licensed or registered. In general, this entails a medical degree from a university and accreditation by a medical board or an equivalent national organization, which may ask the applicant to pass exams. This restricts the considerable legal authority of the medical profession to physicians that are trained and qualified by national standards. It is also intended as an assurance to patients and as a safeguard against charlatans that practice inadequate medicine for personal gain. While the laws generally require medical doctors to be trained in “evidence based”, Western, or Hippocratic Medicine, they are not intended to discourage different paradigms of health.

In the European Union, the profession of doctor of medicine is regulated. A profession is said to be regulated when access and exercise is subject to the possession of a specific professional qualification. The regulated professions database contains a list of regulated professions for doctor of medicine in the EU member states, EEA countries and Switzerland. This list is covered by the Directive 2005/36/EC.

Doctors who are negligent or intentionally harmful in their care of patients can face charges of medical malpractice and be subject to civil, criminal, or professional sanctions.

Medical ethics is a system of moral principles that apply values and judgments to the practice of medicine. As a scholarly discipline, medical ethics encompasses its practical application in clinical settings as well as work on its history, philosophy, theology, and sociology. Six of the values that commonly apply to medical ethics discussions are:

Values such as these do not give answers as to how to handle a particular situation, but provide a useful framework for understanding conflicts. When moral values are in conflict, the result may be an ethical dilemma or crisis. Sometimes, no good solution to a dilemma in medical ethics exists, and occasionally, the values of the medical community (i.e., the hospital and its staff) conflict with the values of the individual patient, family, or larger non-medical community. Conflicts can also arise between health care providers, or among family members. For example, some argue that the principles of autonomy and beneficence clash when patients refuse blood transfusions, considering them life-saving; and truth-telling was not emphasized to a large extent before the HIV era.

Prehistoric medicine incorporated plants (herbalism), animal parts, and minerals. In many cases these materials were used ritually as magical substances by priests, shamans, or medicine men. Well-known spiritual systems include animism (the notion of inanimate objects having spirits), spiritualism (an appeal to gods or communion with ancestor spirits); shamanism (the vesting of an individual with mystic powers); and divination (magically obtaining the truth). The field of medical anthropology examines the ways in which culture and society are organized around or impacted by issues of health, health care and related issues.

Early records on medicine have been discovered from ancient Egyptian medicine, Babylonian Medicine, Ayurvedic medicine (in the Indian subcontinent), classical Chinese medicine (predecessor to the modern traditional Chinese Medicine), and ancient Greek medicine and Roman medicine.

In Egypt, Imhotep (3rd millennium BC) is the first physician in history known by name. The oldest Egyptian medical text is the Kahun Gynaecological Papyrus from around 2000 BCE, which describes gynaecological diseases. The Edwin Smith Papyrus dating back to 1600 BCE is an early work on surgery, while the Ebers Papyrus dating back to 1500 BCE is akin to a textbook on medicine.[24]

In China, archaeological evidence of medicine in Chinese dates back to the Bronze Age Shang Dynasty, based on seeds for herbalism and tools presumed to have been used for surgery.[25] The Huangdi Neijing, the progenitor of Chinese medicine, is a medical text written beginning in the 2nd century BCE and compiled in the 3rd century.[26]

In India, the surgeon Sushruta described numerous surgical operations, including the earliest forms of plastic surgery.[27][dubious discuss][28][29] Earliest records of dedicated hospitals come from Mihintale in Sri Lanka where evidence of dedicated medicinal treatment facilities for patients are found.[30][31]

In Greece, the Greek physician Hippocrates, the “father of western medicine”,[32][33] laid the foundation for a rational approach to medicine. Hippocrates introduced the Hippocratic Oath for physicians, which is still relevant and in use today, and was the first to categorize illnesses as acute, chronic, endemic and epidemic, and use terms such as, “exacerbation, relapse, resolution, crisis, paroxysm, peak, and convalescence”.[34][35] The Greek physician Galen was also one of the greatest surgeons of the ancient world and performed many audacious operations, including brain and eye surgeries. After the fall of the Western Roman Empire and the onset of the Early Middle Ages, the Greek tradition of medicine went into decline in Western Europe, although it continued uninterrupted in the Eastern Roman (Byzantine) Empire.

Most of our knowledge of ancient Hebrew medicine during the 1stmillenniumBC comes from the Torah, i.e.the Five Books of Moses, which contain various health related laws and rituals. The Hebrew contribution to the development of modern medicine started in the Byzantine Era, with the physician Asaph the Jew.[36]

After 750 CE, the Muslim world had the works of Hippocrates, Galen and Sushruta translated into Arabic, and Islamic physicians engaged in some significant medical research. Notable Islamic medical pioneers include the Persian polymath, Avicenna, who, along with Imhotep and Hippocrates, has also been called the “father of medicine”.[37] He wrote The Canon of Medicine, considered one of the most famous books in the history of medicine.[38] Others include Abulcasis,[39]Avenzoar,[40]Ibn al-Nafis,[41] and Averroes.[42]Rhazes[43] was one of the first to question the Greek theory of humorism, which nevertheless remained influential in both medieval Western and medieval Islamic medicine.[44]Al-Risalah al-Dhahabiah by Ali al-Ridha, the eighth Imam of Shia Muslims, is revered as the most precious Islamic literature in the Science of Medicine.[45] The Persian Bimaristan hospitals were an early example of public hospitals.[46][47]

In Europe, Charlemagne decreed that a hospital should be attached to each cathedral and monastery and the historian Geoffrey Blainey likened the activities of the Catholic Church in health care during the Middle Ages to an early version of a welfare state: “It conducted hospitals for the old and orphanages for the young; hospices for the sick of all ages; places for the lepers; and hostels or inns where pilgrims could buy a cheap bed and meal”. It supplied food to the population during famine and distributed food to the poor. This welfare system the church funded through collecting taxes on a large scale and possessing large farmlands and estates. The Benedictine order was noted for setting up hospitals and infirmaries in their monasteries, growing medical herbs and becoming the chief medical care givers of their districts, as at the great Abbey of Cluny. The Church also established a network of cathedral schools and universities where medicine was studied. The Schola Medica Salernitana in Salerno, looking to the learning of Greek and Arab physicians, grew to be the finest medical school in Medieval Europe.[48]

However, the fourteenth and fifteenth century Black Death devastated both the Middle East and Europe, and it has even been argued that Western Europe was generally more effective in recovering from the pandemic than the Middle East.[49] In the early modern period, important early figures in medicine and anatomy emerged in Europe, including Gabriele Falloppio and William Harvey.

The major shift in medical thinking was the gradual rejection, especially during the Black Death in the 14th and 15th centuries, of what may be called the ‘traditional authority’ approach to science and medicine. This was the notion that because some prominent person in the past said something must be so, then that was the way it was, and anything one observed to the contrary was an anomaly (which was paralleled by a similar shift in European society in general see Copernicus’s rejection of Ptolemy’s theories on astronomy). Physicians like Vesalius improved upon or disproved some of the theories from the past. The main tomes used both by medicine students and expert physicians were Materia Medica and Pharmacopoeia.

Andreas Vesalius was the author of De humani corporis fabrica, an important book on human anatomy.[50] Bacteria and microorganisms were first observed with a microscope by Antonie van Leeuwenhoek in 1676, initiating the scientific field microbiology.[51] Independently from Ibn al-Nafis, Michael Servetus rediscovered the pulmonary circulation, but this discovery did not reach the public because it was written down for the first time in the “Manuscript of Paris”[52] in 1546, and later published in the theological work for which he paid with his life in 1553. Later this was described by Renaldus Columbus and Andrea Cesalpino. Herman Boerhaave is sometimes referred to as a “father of physiology” due to his exemplary teaching in Leiden and textbook ‘Institutiones medicae’ (1708). Pierre Fauchard has been called “the father of modern dentistry”.[53]

Veterinary medicine was, for the first time, truly separated from human medicine in 1761, when the French veterinarian Claude Bourgelat founded the world’s first veterinary school in Lyon, France. Before this, medical doctors treated both humans and other animals.

Modern scientific biomedical research (where results are testable and reproducible) began to replace early Western traditions based on herbalism, the Greek “four humours” and other such pre-modern notions. The modern era really began with Edward Jenner’s discovery of the smallpox vaccine at the end of the 18th century (inspired by the method of inoculation earlier practiced in Asia), Robert Koch’s discoveries around 1880 of the transmission of disease by bacteria, and then the discovery of antibiotics around 1900.

The post-18th century modernity period brought more groundbreaking researchers from Europe. From Germany and Austria, doctors Rudolf Virchow, Wilhelm Conrad Rntgen, Karl Landsteiner and Otto Loewi made notable contributions. In the United Kingdom, Alexander Fleming, Joseph Lister, Francis Crick and Florence Nightingale are considered important. Spanish doctor Santiago Ramn y Cajal is considered the father of modern neuroscience.

From New Zealand and Australia came Maurice Wilkins, Howard Florey, and Frank Macfarlane Burnet.

In the United States, William Williams Keen, William Coley, James D. Watson, Italy (Salvador Luria), Switzerland (Alexandre Yersin), Japan (Kitasato Shibasabur), and France (Jean-Martin Charcot, Claude Bernard, Paul Broca) and others did significant work. Russian Nikolai Korotkov also did significant work, as did Sir William Osler and Harvey Cushing.

As science and technology developed, medicine became more reliant upon medications. Throughout history and in Europe right until the late 18th century, not only animal and plant products were used as medicine, but also human body parts and fluids.[54]Pharmacology developed in part from herbalism and some drugs are still derived from plants (atropine, ephedrine, warfarin, aspirin, digoxin, vinca alkaloids, taxol, hyoscine, etc.).[55]Vaccines were discovered by Edward Jenner and Louis Pasteur.

The first antibiotic was arsphenamine (Salvarsan) discovered by Paul Ehrlich in 1908 after he observed that bacteria took up toxic dyes that human cells did not. The first major class of antibiotics was the sulfa drugs, derived by German chemists originally from azo dyes.

Pharmacology has become increasingly sophisticated; modern biotechnology allows drugs targeted towards specific physiological processes to be developed, sometimes designed for compatibility with the body to reduce side-effects. Genomics and knowledge of human genetics is having some influence on medicine, as the causative genes of most monogenic genetic disorders have now been identified, and the development of techniques in molecular biology and genetics are influencing medical technology, practice and decision-making.

Evidence-based medicine is a contemporary movement to establish the most effective algorithms of practice (ways of doing things) through the use of systematic reviews and meta-analysis. The movement is facilitated by modern global information science, which allows as much of the available evidence as possible to be collected and analyzed according to standard protocols that are then disseminated to healthcare providers. The Cochrane Collaboration leads this movement. A 2001 review of 160 Cochrane systematic reviews revealed that, according to two readers, 21.3% of the reviews concluded insufficient evidence, 20% concluded evidence of no effect, and 22.5% concluded positive effect.[56]

Traditional medicine (also known as indigenous or folk medicine) comprises knowledge systems that developed over generations within various societies before the era of modern medicine. The World Health Organization (WHO) defines traditional medicine as “the sum total of the knowledge, skills, and practices based on the theories, beliefs, and experiences indigenous to different cultures, whether explicable or not, used in the maintenance of health as well as in the prevention, diagnosis, improvement or treatment of physical and mental illness.”[57]

In some Asian and African countries, up to 80% of the population relies on traditional medicine for their primary health care needs. When adopted outside of its traditional culture, traditional medicine is often called alternative medicine.[57] Practices known as traditional medicines include Ayurveda, Siddha medicine, Unani, ancient Iranian medicine, Irani, Islamic medicine, traditional Chinese medicine, traditional Korean medicine, acupuncture, Muti, If, and traditional African medicine.

The WHO notes however that “inappropriate use of traditional medicines or practices can have negative or dangerous effects” and that “further research is needed to ascertain the efficacy and safety” of several of the practices and medicinal plants used by traditional medicine systems.[57] The line between alternative medicine and quackery is a contentious subject.

Traditional medicine may include formalized aspects of folk medicine, that is to say longstanding remedies passed on and practised by lay people. Folk medicine consists of the healing practices and ideas of body physiology and health preservation known to some in a culture, transmitted informally as general knowledge, and practiced or applied by anyone in the culture having prior experience.[58] Folk medicine may also be referred to as traditional medicine, alternative medicine, indigenous medicine, or natural medicine. These terms are often considered interchangeable, even though some authors may prefer one or the other because of certain overtones they may be willing to highlight. In fact, out of these terms perhaps only indigenous medicine and traditional medicine have the same meaning as folk medicine, while the others should be understood rather in a modern or modernized context.[59]

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Medicine – Wikipedia

Recommendation and review posted by Bethany Smith

Donating Bone Marrow | Cancer.Net

Bone marrow is a soft, spongy material found in your large bones. It makes more than 200 billion new blood cells every day, including red blood cells, white blood cells, and platelets. But for people with bone marrow disease, including several types of cancer, the process doesnt work properly. Often, a bone marrow transplant is a persons best chance of survival and a possible cure. The good news is that donating bone marrow can be as easy and painless as giving blood.

A bone marrow transplant replaces diseased bone marrow with healthy tissue, usually stem cells found in the blood. Thats why bone marrow transplants are also called stem cell transplants. In an allogeneic transplantation (ALLO transplant), blood stem cells from the bone marrow are transplanted from a donor into the patient. The donor stem cells can come from either the blood that circulates throughout another persons body or from umbilical cord blood.

But theres a catch. Before a person receives an ALLO transplant, a matching donor must be found using human leukocyte antigen (HLA) typing. This special blood test analyzes HLAs, which are specific proteins on the surface of white blood cells and other cells that make each persons tissue type unique. HLA-matched bone marrow is less likely to cause a possible side effect of transplantation called graft vs. host disease (GVHD). GVHD is when immune cells in the transplanted tissue recognize the recipients body as foreign and attack it.

Only about 30% of people who need a transplant can find an HLA-matched donor in their immediate family. For the remaining 70% of people, doctors need to find HLA-matched bone marrow from other donors. In 2016, that equals about 14,000 people from very young children up to older adults in the United States who need to find a donor outside of their close family.

The National Marrow Donor Program (NMDP) has a registry of potential donors that might be the match a patient needs. Heres how the donation process works:

You register with the NMDP online or in person at a donor center. You can find a center by calling the toll-free number 1-800-MARROW2.

You collect cells from your cheek with a cotton swab or provide a small blood sample. This is done by following directions in a mail-in kit or at a donor center. The sample is analyzed to determine your HLA type, which is recorded in the NMDP national database.

If an HLA match is made with a patient in need, the NMDP contacts you. A donor center takes a new sample of your blood, which is sent to the patients transplant center to confirm the HLA match. Once doctors confirm the match, youd meet with a counselor from the NMDP to talk about the procedures, benefits, and risks of the donation process. You then decide whether youre comfortable with donating.

If you agree to donate bone marrow, youll likely do whats called a peripheral blood stem cell (PBSC) collection. Heres how it works:

For 5 days leading up to the donation, youll get a daily 5-minute injection of granulocyte colony-stimulating factor (G-CSF), a white blood cell growth hormone.

On day 5, a trained health care provider will place a needle in each of your arms. One needle will remove blood, and a machine circulates the blood and collects the stem cells. Your blood then is returned to your body through the second needle. The process takes about 3 hours and may be repeated on a second donation day. Side effects include headaches, bone soreness, and discomfort from the needles during the process.

Although less common, some donors may be asked to undergo a bone marrow harvest, during which doctors take bone marrow from the back of a donors hip bone during surgery. Donors usually go home the same day of the surgery and can return to normal activity within 1 week. Common side effects include nausea, headache, and fatigue, most often related to the anesthesia. Bruising or discomfort in the lower back is also common.

The end result? You could help cure someones disease.

Read the rest here:
Donating Bone Marrow | Cancer.Net

Recommendation and review posted by Bethany Smith

Bone Marrow Transplantation | Hematology and Oncology

What is a bone marrow transplant?

Bone marrow transplant (BMT) is a special therapy for patients with certain cancers or other diseases. A bone marrow transplant involves taking cells that are normally found in the bone marrow (stem cells), filtering those cells, and giving them back either to the donor (patient) or to another person. The goal of BMT is to transfuse healthy bone marrow cells into a person after their own unhealthy bone marrow has been treated to kill the abnormal cells.

Bone marrow transplant has been used successfully to treat diseases such as leukemias, lymphomas, aplastic anemia, immune deficiency disorders, and some solid tumor cancers since 1968.

What is bone marrow?

Bone marrow is the soft, spongy tissue found inside bones. It is the medium for development and storage of most of the body’s blood cells.

The blood cells that produce other blood cells are called stem cells. The most primitive of the stem cells is called the pluripotent stem cell, which is different than other blood cells with regards to the following properties:

It is the stem cells that are needed in bone marrow transplant.

Why is a bone marrow transplant needed?

The goal of a bone marrow transplant is to cure many diseases and types of cancer. When the doses of chemotherapy or radiation needed to cure a cancer are so high that a person’s bone marrow stem cells will be permanently damaged or destroyed by the treatment, a bone marrow transplant may be needed. Bone marrow transplants may also be needed if the bone marrow has been destroyed by a disease.

A bone marrow transplant can be used to:

The risks and benefits must be weighed in a thorough discussion with your doctor and specialists in bone marrow transplants prior to procedure.

What are some diseases that may benefit from bone marrow transplant?

The following diseases are the ones that most commonly benefit from bone marrow transplant:

However, patients experience diseases differently, and bone marrow transplant may not be appropriate for everyone who suffers from these diseases.

What are the different types of bone marrow transplants?

There are different types of bone marrow transplants depending on who the donor is. The different types of BMT include the following:

How are a donor and recipient matched?

Matching involves typing human leukocyte antigen (HLA) tissue. The antigens on the surface of these special white blood cells determine the genetic makeup of a person’s immune system. There are at least 100 HLA antigens; however, it is believed that there are a few major antigens that determine whether a donor and recipient match. The others are considered “minor” and their effect on a successful transplant is not as well-defined.

Medical research is still investigating the role all antigens play in the process of a bone marrow transplant. The more antigens that match, the better the engraftment of donated marrow. Engraftment of the stem cells occurs when the donated cells make their way to the marrow and begin producing new blood cells.

Most of the genes that “code” for the human immune system are on one chromosome. Since we only have two of each chromosome, one we received from each of our parents, a full sibling of a patient in need of a transplant has a one in four chance of having gotten the same set of chromosomes and being a “full match” for transplantation.

The bone marrow transplant team

The group of specialists involved in the care of patients going through transplant is often referred to as the transplant team. All individuals work together to provide the best chance for a successful transplant. The team consists of the following:

An extensive evaluation is completed by the bone marrow transplant team. The decision for you to undergo a bone marrow transplant will be based on many factors, including the following:

For a patient receiving the transplant, the following will occur in advance of the procedure:

Preparation for the donor

How are the stem cells collected?

A bone marrow transplant is done by transferring stem cells from one person to another. Stem cells can either be collected from the circulating cells in the blood (the peripheral system) or from the bone marrow.

If the donor is the person himself or herself, it is called an autologous bone marrow transplant. If an autologous transplant is planned, previously collected stem cells, from either peripheral (apheresis) or harvest, are counted, screened, and ready to infuse.

The bone marrow transplant procedure

The preparations for a bone marrow transplant vary depending on the type of transplant, the disease requiring transplant, and your tolerance for certain medications. Consider the following:

The days before transplant are counted as minus days. The day of transplant is considered day zero. Engraftment and recovery following the transplant are counted as plus days. For example, a patient may enter the hospital on day -8 for preparative regimen. The day of transplant is numbered zero. Days +1, +2, etc., will follow. There are specific events, complications, and risks associated with each day before, during, and after transplant. The days are numbered to help the patient and family understand where they are in terms of risks and discharge planning.

During infusion of bone marrow, the patient may experience the following:

After infusion, the patient may:

After leaving the hospital, the recovery process continues for several months or longer, during which time the patient cannot return to work or many previously enjoyed activities. The patient must also make frequent follow-up visits to the hospital or doctor’s office.

When does engraftment occur?

Engraftment of the stem cells occurs when the donated cells make their way to the marrow and begin producing new blood cells. Depending on the type of transplant and the disease being treated, engraftment usually occurs around day +15 or +30. Blood counts will be checked frequently during the days following transplant to evaluate initiation and progress of engraftment. Platelets are generally the last blood cell to recover.

Engraftment can be delayed because of infection, medications, low donated stem cell count, or graft failure. Although the new bone marrow may begin making cells in the first 30 days following transplant, it may take months, even years, for the entire immune system to fully recover.

What complications and side effects may occur following BMT?

Complications may vary, depending on the following:

The following are complications that may occur with a bone marrow transplant. However, each individual may experience symptoms differently. These complications may also occur alone, or in combination:

Long-term outlook for a bone marrow transplantation

Prognosis greatly depends on the following:

As with any procedure, in bone marrow transplant the prognosis and long-term survival can vary greatly from person to person. The number of transplants being done for an increasing number of diseases, as well as ongoing medical developments, have greatly improved the outcome for bone marrow transplant in children and adults. Continuous follow-up care is essential for the patient following a bone marrow transplant. New methods to improve treatment and to decrease complications and side effects of a bone marrow transplant are continually being discovered.

More here:
Bone Marrow Transplantation | Hematology and Oncology

Recommendation and review posted by sam

Cell Science & Therapy –

Index Copernicus Value: 5.12

NLMID: 101550241

The Journal of Cell Science & Therapy is an Open Access, peer-reviewed, academic journal with a wide range of fields within the discipline creates a platform for the authors to publish their comprehensive and most reliable source of information on the discoveries and current developments in the mode of original articles, review articles, case reports, short communications, etc, making them freely available through online without any restrictions or any other subscriptions to researchers worldwide.

The journal is using Editorial Manager System for quality in peer review process. Editorial Manager is an online manuscript submission, review and tracking systems. Review processing is performed by the editorial board members of Journal of Cell Science & Therapy or outside experts; at least two independent reviewers approval followed by editor approval is required for acceptance of any citable manuscript. Authors may submit manuscripts and track their progress through the system, hopefully to publication. Reviewers can download manuscripts and submit their opinions to the editor. Editors can manage the whole submission/review/revise/publish process.

Journal of Cell Science & Therapy is a peer reviewed scientific journal known for rapid dissemination of high-quality research. This Cell Science journal with highest impact factor offers an Open Access platform to the authors in academia and industry to publish their novel research. It serves the International Scientific Community with its standard research publications.

Cells are small compartments that hold the biological equipment necessary to keep an organism alive and successful. Living things may be unicellular or multicellular such as a human being. According to cell theory, cells are the fundamental unit of structure and function in all living organisms and come from preexisting cells, and that all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.

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The cytokines produced by expression from suitable cloning vectors containing the desired cytokine gene, can be expressed in yeast (Saccharomyces cerevisiae expression system), bacteria (Escherichia coli expression system), mammalian cells (BHK, CHO, COS, Namalwa), or insect cell systems. Cytokines are designed for demanding applications such as cell culture, differentiation studies, and functional assays mainly in the fields of immunology, neurology, and stem cell research.

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Hematology is the investigation of blood, the blood-framing organs, and blood diseases in which the specialists deal with the diagnosis, treatment and overall management of people with blood disorders ranging from anemia to blood cancer. Some of the diseases treated by haematologists include Iron deficiency anaemia, Sickle cell anemia, Polycythemia or excess production of red blood cells, Myelofibrosis, Leukemia, hemophilia, myelodysplastic syndromes, Malignant lymphomas, Blood transfusion and bone marrow stem cell transplantation

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Cell biology (cytology) is a branch of biology that studies cells their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division, death and cell function. Research in cell biology is closely related to genetics, biochemistry, molecular biology, immunology, and developmental biology.

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A hair follicle is part of the skin that grows hair by packing old cells together. Attached to the follicle is a sebaceous gland, a tiny sebum-producing gland found everywhere except on the palms, lips and soles of the feet. The follicle cells that extrude hairs from just below the surface of the skin are simply too hard to bring back to life, and even preventative therapies didnt seem to be able to do much to keep them alive. But research on inducing stem cells to grow into follicle cells could change that forever.

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Mesenchymal stem cells (MSCs), the major stem cells for cell therapy. From animal models to clinical trials, MSCs have afforded promise in the treatment of numerous diseases, mainly tissue injury and immune disorders. Cell sources for MSC administration in clinical applications, and provide an overview of mechanisms that are significant in MSC-mediated therapies. Although MSCs for cell therapy have been shown to be safe and effective, there are still challenges that need to be tackled before their wide application in the clinical research field.

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Ovation Cell Therapy Hair Treatment nourishes hair and scalp with proteins and amino acids that bind and absorb into the hair shaft for hair that is noticeably thicker, stronger, and longer. The Ovation Cell Therapy is the heart of the system and is often where the system draws occasional criticism for its claims to accelerate hair growth and reduce breakage and hair loss.

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Rejuvenation and regeneration are two key processes that define cell therapy. Cellular Therapy is a form of non-toxic, holistic medicine in which the entire organism is being treated. Cellular Therapies are an integral part of complimentary treatment regimens. They are extremely versatile and can be used for a wide range of disorders.

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The cells are most commonly immune-derived, with the goal of transferring immune functionality and characteristics along with the cells. Transferring autologous cells minimizes GVHD issues. The adaptive transfer of autologous tumor infiltrating lymphocytes (TIL) or genetically re-directed peripheral blood mononuclear cells has been used to treat patients with advanced solid tumors, including melanoma and colorectal carcinoma, as well as patients with CD19-expressing hematologic malignancies. As of 2015 the technique had expanded to treat cervical cancer, lymphoma, leukemia, bile duct cancer and neuroblastoma.

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Advance Cell & Gene Thearpy practical, experienced guidance in development, GMP/GTP manufacturing, and regulatory compliance, as well as comprehensive scientific and technical strategic analysis of business opportunities in cell therapy, gene therapy and tissue therapies.

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Cell Science & Therapy, Insights in Cell Science, Cell Biology: Research & Therapy, Cytology & Histology, Archives of Surgical Oncology, Annals of Cancer Research and Therapy, Cancer Biology and Therapy, Oncology and Stem Cell Therapy, Chinese Journal of Cancer Biotherapy, Current Cancer Therapy Reviews

Immunotherapy involves engineering patients own immune cells to recognize and attack their tumors. And although this approach, called adoptive cell transfer (ACT), has been restricted to small clinical trials so far, treatments using these engineered immune cells have generated some remarkable responses in patients with advanced cancer. .Adoptive T cell therapy for cancer is a form of transfusion therapy consisting of the infusion of various mature T cell subsets with the goal of eliminating a tumor and preventing its recurrence.

Related Journals of Immune Cell Therapy

Clinical & Cellular Immunology, Immunooncology, Molecular Immunology, Advances in Cancer Prevention, Cytotherapy, Journal of Acquired Immune Deficiency Syndromes, Advances in Neuroimmune Biology, Cancer Biology and Therapy, Cancer Immunology, Immunotherapy

Commercialization of the first cell-based therapeutics, including cartilage repair products; tissue-engineered skin; and the first personalized, cellular immunotherapy for cancer. Production, storage, and delivery of living cell-based pharmaceuticals presents several unique challenges. Novel, innovative technologies and strategies will be required to bring cell therapies to commercial success.

Related Journals of Cell Therapy Bioprocessing

Bioprocessing & Biotechniques, Cytology & Histology, Cell Biology: Research & Therapy , Molecular Biology, BioProcess International, Biotechnology and Bioprocess Engineering, Food and Bioprocess Technology, Industrial Bioprocessing

Cellular therapy products include cellular immunotherapies, and other types of both autologous and allogeneic cells for certain therapeutic indications, including adult and embryonic stem cells. Human gene therapy refers to products that introduce genetic material into a persons DNA to replace faulty or missing genetic material, thus treating a disease or abnormal medical condition.

Related Journals of Cell Therapy Products

Pharmacognosy & Natural Products, Natural Products Chemistry & Research, Stem Cell Research & Therapy, Cell Science & Therapy, Surgical Products, International Journal of Applied Research in Natural Products, Molecular Diagnosis and Therapy, Molecular Therapy, Molecular Therapy – Nucleic Acids

Journal of Cell Science and Therapy is associated with our international conference “6th World Congrss on Cell & Stem Cell Research” during Feb 29- March 2, 2016 Philadelphia, USA with a theme “Novel Therapies in Cell Science and Stem Cell Research. Stem Cell Therapy-2016 will encompass recent researches and findings in stem cell technologies, stem cell therapies and transplantations, current understanding of cell plasticity in cancer and other advancements in stem cell research and cell science.

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Breast CancerPatient Version – National Cancer Institute

The breast is made up of glands called lobules that can make milk and thin tubes called ducts that carry the milk from the lobules to the nipple. Breast tissue also contains fat and connective tissue, lymph nodes, and blood vessels.

The most common type of breast cancer is ductal carcinoma, which begins in the cells of the ducts. Breast cancer can also begin in the cells of the lobules and in other tissues in the breast. Ductal carcinoma in situ is a condition in which abnormal cells are found in the lining of the ducts but they haven’t spread outside the duct. Breast cancer that has spread from where it began in the ducts or lobules to surrounding tissue is called invasive breast cancer. In inflammatory breast cancer, the breast looks red and swollen and feels warm because the cancer cells block the lymph vessels in the skin.

In the U.S., breast cancer is the second most common cancer in women after skin cancer. It can occur in both men and women, but it is rare in men. Each year there are about 100 times more new cases of breast cancer in women than in men.

Key statistics about breast cancer from the SEER Cancer Statistics Review, 1975-2010.

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Gene Therapy Research – Dana-Farber/Boston Children’s …

Gene Therapy Phone: 617-632-5064

From the first attempt at modifying human DNA in the early 1980s to the first clinical trials based on genetic engineering of the mid 1990s to the first commercialization of a genetically engineered cell product in 2002 gene therapy has moved from being a pioneering research field to becoming one of the most technologically advanced and promising clinical realities for the treatment of a wide spectrum of diseases and tumors.

Founded in 2010, our Gene Therapy Program has been at the forefront of the fight against rare genetic disorders affecting children. The success of our gene therapy clinical trials is due to our programs unique combination of basic research and clinical care and our ability to translate what we learn at the laboratory bench to the bedside care of the patients we treat.

Through our research capabilities and partnerships, we strive to excel in every step of the gene therapy process. Our research includes:

We work closely with industrial and translational academic partners, such as the Translab and Cell Manipulation cores at Dana-Farber Cancer Institute, to:

Learn more

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Gene Therapy –

In amyotrophic lateral sclerosis (ALS), gene therapy may help if it can deliver a beneficial protein to salvage dying nerve cells. Gene therapy can be simply a means to boost on site production of a helpful factor, at places where nerve cells are in trouble. Researchers can disarm many types of viruses, and put in the genetic instructions to make therapeutic protein. The redesigned viruses are called vectors. They are simply carriers for therapeutic genes. Knowledge of the SOD1 mutations linked to some forms of ALS has produced a vast body of evidence, pointing to a general strategy for the disease that might be successfully implemented through gene therapy.

Gene therapy is the use of genetic instructions to produce a protein to treat a disorder or deficiency. It can aid in a disease even if the therapy is not directly targeting a gene defect that causes the disease. In amyotrophic lateral sclerosis (ALS), gene therapy may help if it can deliver a beneficial protein, to salvage dying nerve cells. The gene therapy simply is a means to boost on site production of a trophic (growth enhancing) factor, at places where nerve cells are in trouble.

Genes are the molecules in all cells of our bodies that carry the instructions to make all of the materials that comprise the body. In the 1950s, scientists determined that genes code precisely for proteins, with a sequence that specifies the order of the building blocks of proteins, the amino acids. Each gene corresponds to a protein. Each base in a gene codes for an amino acid. The order of bases in a gene produces the ordered chain of amino acids that produce a working protein.

At the turn of the current century, scientists determined, in rough draft form, the sequence of all of the human genes. By this time, they also knew how to create a gene construct, and move that construct into cells, to get the cells to make the corresponding protein.

In some diseases, researchers already know that a defective gene is not able to work. They have the potential means to cure the disease, by replacing the defective gene with a correct, working copy. In ALS, only a few percent of patients have a known gene defect. For the rest, it may be one undiscovered gene that is the problem, or it may be several. But gene therapy can still be designed to aid patients with ALS by providing supportive proteins for nerve cells.

Genes normally reside in the nucleus, the core of a cell, separated from the surrounding materials by a membrane. The chromosomes are the structures within the cell nucleus that contain the DNA that comprises the genes. It is very challenging to get a gene made in the lab to cross both the outer envelope of a cell, and the nuclear membrane as well, to reach the chromosomes.

Scientists studying viruses have discovered natures own solution to the problem of moving genes. Viruses are essentially genes that have evolved to hijack cells, instead of forming cells for themselves. So viruses have strategies to enter cells and take over the protein production process, to produce instead, the virus. Researchers have figured out how to use viruses as Trojan horses, to bring in genes that can then carry out genetic repairs, replacing defective DNA.

For many viruses, researchers can disarm the genes responsible for the damaging properties and put in, instead, genetic instructions to make therapeutic proteins. These viruses, redesigned by researchers, are called vectors. They are simply a means to smuggle in therapeutic genes.

Investigators must demonstrate that the viral vector is not going to revert back to an infectious form, or cause any side effects.

Genes normally are read out only when a protein is needed, and operate under feedback control. If adequate amounts of protein are already there, then the gene is turned off. Scientists have to be able to devise the proper switch elements to accompany a therapeutic gene, to make sure that a gene is expressed in proper amounts, and only in an intended target tissue.

To gauge adequate delivery of the vector, and sufficient levels of gene expression, researchers have to have animal models that reflect the key manifestations of a human disease. Despite preclinical work with animals, it is not always possible to extrapolate to patients.

A patients immune system may mount an attack on viral vectors (after all, that is what the immune system is primed to do), or on the newly introduced therapeutic gene product.

In ALS, a few percent of patients have a known defect in a gene. This genetic mistake, in the gene coding for the SOD1 protein, produces disease no different from any other form of ALS, inherited or not. Gene therapy might be designed for a particular SOD1 defect, but that therapy may or may not work for other ALS patients.

What is encouraging is that the knowledge of the SOD1 mutations has produced a vast body of evidence for what does go wrong in other cases of ALS. And that evidence is pointing to a general strategy that might be successfully implemented through gene therapy.

ALS research has produced the notion that the neighborhood surrounding the motor neurons can be nurturing or detrimental to these crucial cells affected in ALS. Even if a neuron carries a mutated SOD1 gene, that nerve cell can survive if neighboring support cells, the glia, have the normal gene (see section on Cell Targets).

Glial cells surround neurons. Some glial functions produce the hallmarks of damage in the nervous system, either inflammation or scarring. Other glial actions are protective, for instance, sweeping away excess excitatory signal molecules before they can do damage. Gene therapy in ALS may be able to target the glial cells as well as neurons, to produce positive effects.

Studies in animal models of ALS show increased survival after treatment with trophic factors (see section on trophic factors), small proteins that support the growth and metabolic activities of nerve cells, most recently with IGF-1 and also after vascular endothelial growth factor (VEGF). However, clinical trials of trophic factors in ALS patients have been disappointing. The challenge of delivering these proteins to the site of damage is likely the underlying cause of the failures in the clinic.

Gene therapy may be the way to provide a steady supply of trophic factors to neurons damaged in ALS, directly at the place where the damage exists. The ALS Association is supporting various avenues of research that seek to implement gene therapies to deliver trophic factors, and is encouraging entry into clinical trials as quickly as possible.

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7 Major Advancements 3D Printing Is Making in the Medical …

3D printing may seem a little unfathomable to some, especially when you apply biomedical engineering to 3D printing. In general, 3D printing involves taking a digital model or blueprint created via software, which is then printed in successive layers of materials like glass, metal, plastic, ceramic and assembled one layer at a time. Many major manufacturers use them to manufacture airplane parts or electrical appliances.

Some of the most incredible uses for 3D printing are developing within the medical field. Some of the following ways this futuristic technology is being developed for medical use might sound like a Michael Crichton novel, but are fast becoming reality.

Bioprinting is based on bio-ink, which is made of living cell structures. When a particular digital model is input, specific living tissue is printed and built up layer by cell layer. Bioprinting research is being developed to print different types of tissue, while 3D inkjet printing is being used to develop advanced medical devices and tools.

While an entire organ has yet to be successfully printed for practical surgical use, scientists and researchers have successfully printed kidney cells, sheets of cardiac tissue that beat like a real heart and the foundations of a human liver, among many other organ tissues. While printing out an entire human organ for transplant may still be at least a decade away, medical researchers and scientists are well on their way to making this a reality.

Stem cells have amazing regenerative properties already they can reproduce many different kinds of human tissue. Now, stem cells are being bioprinted in several university research labs, such as the Heriot-Watt University of Edinburgh. Stem cell printing was the precursor to printing other kinds of tissues, and could eventually lead to printing cells directly into parts of the body.

Imagine the uses that printing skin grafts could do for burn victims, skin cancer patients and other kinds of afflictions and diseases that affect the epidermis. Medical engineers in Germany have been developing skin cell bioprinting since 2010, and researcher James Yoo from Wake Forest Institute is developing skin graft printing that can be applied directly onto burn victims.

Hod Lipson, a Cornell engineer, prototyped tissue bioprinting for cartilage within the past few years. Though Lipson has yet to bioprint a meniscus that can withstand the kind of pressure and pounding that a real one can, he and other engineers are well on their way to understanding how to apply these properties. Additionally, the same group from Germany who bioprinted stem cells is also working toward the same results for bioprinting bone and others parts of the skeletal system.

Just six months ago, bioengineering students from the University of British Columbia won a prestigious award for their engineering and 3D printing of a new and extremely effective type of surgical smoke evacuator. Other surgical tools that have been 3D printed include forceps, hemostats, scalpel handles and clamps and best of all, they come out of the printer sterile and cost a tenth as much as the stainless steel equivalent.

In the same way that tissue and types of organ cells are being printed and studied, disease cells and cancer cells are also being bioprinted, in order to more effectively and systematically study how tumors grow and develop. Such medical engineering would allow for better drug testing, cancer cell analyzing and therapy development. With developments in 3D and bioprinting, it may even be a possibility within our lifetime that a cure for cancer is discovered.

Another German institute has created blood vessels using artificial biological cells, a 3D inkjet printer and a laser to mold them into shape. Likewise, researchers at the University of Rostock in Germany, Harvard Medical Institute and the University of Sydney are developing methods of heart repair, or types of a heart patch, made with 3D printed cells.

The human cell heart patches have gone through successful testing on rats, and have also included development of artificial cardiac tissues that successfully mimic the mechanical and biological properties of a real human heart.

There are plenty of other developments being made with 3D and bioprinting, but one of the biggest obstacles is finding software that is advanced or sophisticated enough to meet the challenge of creating the blueprint. While creating the blueprint for an ash tray, and subsequently producing it via 3D printing is a fairly simple and quick process, there is no equivalent for creating digital models of a liver or heart at this point.

However, with the quick developments and advancements researchers and biomedical engineers have made in a short few years, this obstacle will soon be one of many that are overcome on the way to successful complex bioprinting.

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You & Your Hormones | Endocrine conditions | Male hypogonadism

Male hypogonadism is the result of deficiency of the male sex hormone testosterone. It leads to loss of sex drive and function, delayed puberty, osteoporosis, and there can also be associated failure of the testes to produce sperm.

Testosterone deficiency syndrome; testosterone deficiency; primary hypogonadism; secondary hypogonadism; hypergonadotrophic hypogonadism; hypogonadotrophic hypogonadism.

Male hypogonadism describes a state of low levels of the male hormone testosterone in men. Testosterone is produced in the testes and is important for the formation of male characteristics such as deepening of the voice, development of facial and pubic hair and growth of the penis and testes during puberty. Gonadotrophin-releasing hormone made in the hypothalamus stimulates the pituitary gland to produce luteinising hormone and follicle stimulating hormone (gonadotrophins), which then act on the testes causing them to produce testosterone.Low levels of testosterone can occur due to disease of the testes or from conditions affecting the hypothalamus or pituitary gland. Men can be affected at any age and present with different symptoms depending on the timing of the disease in relation to the start of puberty.

Male hypogonadism can be divided into two groups.Classical hypogonadism is where the low levels of testosterone are caused by an underlying specific medical condition, for example Klinefelter’s syndrome, Kallmanns syndrome or a pituitary tumour.Late-onset hypogonadism is where the decline in testosterone levels is linked to general ageing and/or age-related diseases, particularly obesity.It is estimated that late-onset hypogonadism only affects a small number of men over the age of 40.

There are two types of classical male hypogonadism primary and secondary.Primary hypogonadism occurs when the low level of testosterone is due to conditions affecting the testes.Primary hypogonadism is also referred to as hypergonadotrophic hypogonadism, whereby the pituitary produces too much luteinising hormone and follicle stimulating hormone (gonadotrophins) to try and stimulate the testes to produce more testosterone. However, as the testes are impaired or missing, they are not able to respond to the increased levels of gonadotrophins and little or no testosterone is produced.

Examples of conditions affecting the testes, which lead to low levels of testosterone, include:

Secondary hypogonadism results from conditions affecting the function of the hypothalamus and/or pituitary gland.It is also known as hypogonadotrophic hypogonadism due to low levels of luteinising hormone and follicle stimulating hormone resulting in decreased testosterone production.Secondary hypogonadism often occurs as part of a wider syndrome of hypopituitarism.Examples of causes can include:

The signs and symptoms depend on the stage at which the patient presents with hypogonadism in relation to sexual maturity.If testosterone deficiency occurs before or during puberty, signs and symptoms are likely to include:

Around the time of puberty, boys with too little testosterone may also have less than normal strength and endurance, and their arms and legs may continue to grow out of proportion with the rest of their body.

In men who have already reached sexual maturity, symptoms are likely to include:

As some of these symptoms (e.g. tiredness, mood changes) can have multiple causes, diagnosis of male hypogonadism may sometimes get missed initially.

Male hypogonadism is more common in ageing men. The levels of testosterone in men start to fall after the age of 40. It has been estimated that 8.4% of men aged 50-79 years have testosterone deficiency.Male hypogonadism is also linked with type 2 diabetes: approximately 17% of men with type 2 diabetes are estimated to have low testosterone levels.

Male hypogonadism does not run in families.There are genetic causes of hypogonadism which include Klinefelters syndrome and Kallmanns syndrome; however, these conditions occur sporadically, they are not inherited from the parents.

A detailed medical history should be taken.In particular, it is important to find out if virilisation was complete at birth, whether the testes descended and to see if the patient went through puberty at the same time as his peers. The patient should be thoroughly examined and the presence and size of the testes recorded and whether they are correctly positioned in the scrotum.

Many of the symptoms of male hypogonadism are non-specific and can be caused by a range of conditions. Therefore, when diagnosing hypogonadism, it is important that biochemical tests are performed to assess the levels of testosterone in the blood to confirm diagnosis. Blood tests will be carried out to measure testosterone levels.The blood sample should be collected preferably at 9am (this is because levels of testosterone change throughout the day) and can be carried out as an outpatient appointment.If the result of the first test shows a low level of testosterone, the test should be repeated after two or three weeks to confirm the result. Other hormones are also tested along with the second blood sample. These hormones include luteinising hormone, follicle stimulating hormone and prolactin (produced by the pituitary gland).The results of these blood tests will help distinguish between primary (low testosterone and high gonadotrophins) and secondary (low testosterone and normal or low gonadotrophins) hypogonadism.

Depending on the findings of the above tests, other investigations may be carried out. These include: a bone densitometry test to assess the impact of testosterone deficiency on bone; semen analysis; genetic studies; and an ultrasound of the testes to check for nodules or growths.

Treatment of classical hypogonadism involves replacement of testosterone with the aim of raising the level of testosterone in the blood to normal levels.Exact treatment will vary between patients and be tailored to their individual needs.Different preparations of testosterone are available:

All these are outpatient treatments. All of these options should be discussed with a medical professional and the most appropriate treatment option chosen.During treatment with testosterone replacement, regular blood tests should be carried out to monitor testosterone levels and if necessary, the dose adjusted to ensure levels return to the normal range.Tablet forms of testosterone taken by mouth are not recommended due to a link with liver damage.

Testosterone should not be given if the patient has prostate cancer. Before starting treatment with testosterone, a blood test to measure a hormone produced by the prostate called PSA (prostate-specific antigen) is carried out (PSA levels are elevated in prostate cancer).The prostate may also be examined (via the back passage) to rule out prostate cancer.

For patients who have been diagnosed with late-onset hypogonadism, there is currently not enough evidence for us to know whether treatment with testosterone is safe and effective over the long-term.While there are some short-term studies that indicate it may benefit these patients over a short period of time, there is a need for longer-term clinical trials in this area, following a large number of patients, to assess the long-term impact of testosterone treatment on patients with late-onset hypogonadism. Areas that particularly require focus are assessing the effects of treatment on the likelihood of developing cardiovascular disease, prostate cancer and secondary polycythaemia (a condition where too many red blood cells are present in the blood).

If patients have any concerns about their health, they should contact their GP in the first instance.

There can be mild side-effects of testosterone replacement depending on the form used: injectable forms can cause pain and bruising at site of injection; the gel form can cause skin irritation; and the buccal form can cause gum irritation.

Treatment with testosterone can cause an increase in red blood cells (known as polycythaemia) which increases the risk of thrombosis.Regular blood tests should be carried out during treatment to check for an increase in red blood cells.Enlargement of the prostate is another serious side-effect that should be monitored.Prostate examination and a blood test for PSA should be performed every three months for the first year and then annually in men over the age of 40 years after starting treatment.If patients have any concerns about these possible side-effects, they should discuss them with their doctor.

Symptoms of male hypogonadism such as lack of sex drive, inadequate erections and infertility can lead to low self-esteem and cause depression. Professional counselling is available to help deal with these side-effects; patients should talk to their doctor for more information.Patients generally see an improvement in their sex drive and self-esteem following testosterone replacement therapy.

Male hypogonadism has been linked with an increased risk of developing heart disease (low testosterone can cause an increase in cholesterol levels). Studies have shown that testosterone levels can be lower in men with type 2 diabetes and in men with excess body weight.Lifestyle changes to reduce weight and increase exercise can raise testosterone levels in men with diabetes.

Testosterone levels in men decline naturally as they age.In the media, this is sometimes referred to as the male menopause (andropause).Low testosterone levels can also cause difficulty with concentration, memory loss and sleep difficulties.Current research suggests that this effect occurs in only a small group of ageing men.However, there is a lot of research in progress to find out more about the effects of testosterone in older men and also whether the use of testosterone replacement therapy would have any benefits.

Reviewed: December 2014

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Drosophila melanogaster – Wikipedia

Drosophila melanogaster is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting with Charles W. Woodworth’s proposal of the use of this species as a model organism, D. melanogaster continues to be widely used for biological research in studies of genetics, physiology, microbial pathogenesis, and life history evolution. It is typically used because it is an animal species that is easy to care for, has four pairs of chromosomes, breeds quickly, and lays many eggs.[2]D. melanogaster is a common pest in homes, restaurants, and other occupied places where food is served.[3]

Flies belonging to the family Tephritidae are also called “fruit flies”. This can cause confusion, especially in Australia and South Africa, where the Mediterranean fruit fly Ceratitis capitata is an economic pest.

Wildtype fruit flies are yellow-brown, with brick-red eyes and transverse black rings across the abdomen. They exhibit sexual dimorphism: females are about 2.5 millimeters (0.098in) long; males are slightly smaller with darker backs. Males are easily distinguished from females based on colour differences, with a distinct black patch at the abdomen, less noticeable in recently emerged flies (see fig.), and the sexcombs (a row of dark bristles on the tarsus of the first leg). Furthermore, males have a cluster of spiky hairs (claspers) surrounding the reproducing parts used to attach to the female during mating. There are extensive images at FlyBase.[4]

Egg of D. melanogaster

The D. melanogaster lifespan is about 30 days at 29C (84F).

The developmental period for D. melanogaster varies with temperature, as with many ectothermic species. The shortest development time (egg to adult), 7 days, is achieved at 28C (82F).[5][6] Development times increase at higher temperatures (11 days at 30C or 86F) due to heat stress. Under ideal conditions, the development time at 25C (77F) is 8.5 days,[5][6][7] at 18C (64F) it takes 19 days[5][6] and at 12C (54F) it takes over 50 days.[5][6] Under crowded conditions, development time increases,[8] while the emerging flies are smaller.[8][9] Females lay some 400 eggs (embryos), about five at a time, into rotting fruit or other suitable material such as decaying mushrooms and sap fluxes. The eggs, which are about 0.5mm long, hatch after 1215 hours (at 25C or 77F).[5][6] The resulting larvae grow for about 4 days (at 25C) while molting twice (into second- and third-instar larvae), at about 24 and 48 h after hatching.[5][6] During this time, they feed on the microorganisms that decompose the fruit, as well as on the sugar of the fruit itself. The mother puts feces on the egg sacs to establish the same microbial composition in the larvae’s guts which has worked positively for herself.[10] Then the larvae encapsulate in the puparium and undergo a four-day-long metamorphosis (at 25C), after which the adults eclose (emerge).[5][6]

Females become receptive to courting males at about 812 hours after emergence.[11] Specific neuron groups in females have been found to affect copulation behavior and mate choice. One such group in the abdominal nerve cord allows the female fly to pause her body movements to copulate.[12] Activation of these neurons induces the female to cease movement and orient herself towards the male to allow for mounting. If the group is inactivated, the female remains in motion and does not copulate. Various chemical signals such as male pheromones often are able to activate the group.[12]

The female fruit fly prefers a shorter duration when it comes to sex. Males, on the other hand, prefer it to last longer.[13] Males perform a sequence of five behavioral patterns to court females. First, males orient themselves while playing a courtship song by horizontally extending and vibrating their wings. Soon after, the male positions itself at the rear of the female’s abdomen in a low posture to tap and lick the female genitalia. Finally, the male curls its abdomen and attempts copulation. Females can reject males by moving away, kicking, and extruding their ovipositor.[14] Copulation lasts around 1520 minutes,[15] during which males transfer a few hundred, very long (1.76mm) sperm cells in seminal fluid to the female.[16] Females store the sperm in a tubular receptacle and in two mushroom-shaped spermathecae; sperm from multiple matings compete for fertilization. A last male precedence is believed to exist in which the last male to mate with a female sires about 80% of her offspring. This precedence was found to occur through both displacement and incapacitation.[17] The displacement is attributed to sperm handling by the female fly as multiple matings are conducted and is most significant during the first 12 days after copulation. Displacement from the seminal receptacle is more significant than displacement from the spermathecae.[17] Incapacitation of first male sperm by second male sperm becomes significant 27 days after copulation. The seminal fluid of the second male is believed to be responsible for this incapacitation mechanism (without removal of first male sperm) which takes effect before fertilization occurs.[17] The delay in effectiveness of the incapacitation mechanism is believed to be a protective mechanism that prevents a male fly from incapacitating its own sperm should it mate with the same female fly repetitively. Sensory neurons in the uterus of female D. melanogaster respond to a male protein, sex peptide, which is found in sperm.[12] This protein makes the female reluctant to copulate for about 10 days after insemination. The signal pathway leading to this change in behavior has been determined. The signal is sent to a brain region that is a homolog of the hypothalamus and the hypothalamus then controls sexual behavior and desire[12]

D. melanogaster is often used for life extension studies, such as to identify genes purported to increase lifespan when mutated.[18]

D. melanogaster females exhibit mate choice copying. When virgin females are shown other females copulating with a certain type of male, they tend to copulate more with this type of male afterwards than naive females (which have not observed the copulation of others). This behavior is sensitive to environmental conditions, and females copy less in bad weather conditions.[19]

D. melanogaster males exhibit a strong reproductive learning curve. That is, with sexual experience, these flies tend to modify their future mating behavior in multiple ways. These changes include increased selectivity for courting only intraspecifically, as well as decreased courtship times.

Sexually nave D. melanogaster males are known to spend significant time courting interspecifically, such as with D. simulans flies. Nave D. melanogaster will also attempt to court females that are not yet sexually mature, and other males. D. melanogaster males show little to no preference for D. melanogaster females over females of other species or even other male flies. However, after D. simulans or other flies incapable of copulation have rejected the males advances, D. melanogaster males are much less likely to spend time courting nonspecifically in the future. This apparent learned behavior modification seems to be evolutionarily significant, as it allows the males to avoid investing energy into futile sexual encounters.[20]

In addition, males with previous sexual experience will modify their courtship dance when attempting to mate with new females the experienced males spend less time courting and therefore have lower mating latencies, meaning that they are able to reproduce more quickly. This decreased mating latency leads to a greater mating efficiency for experienced males over nave males.[21] This modification also appears to have obvious evolutionary advantages, as increased mating efficiency is extremely important in the eyes of natural selection.

Both male and female D. melanogaster act polygamously (having multiple sexual partners at the same time).[22] In both males and females, polygamy results in a decrease in evening activity compared to virgin flies, more so in males than females.[22] Evening activity consists of the activities that the flies participate in other than mating and finding partners, such as finding food.[23] The reproductive success of males and females varies, due to the fact that a female only needs to mate once to reach maximum fertility.[23] Mating with multiple partners provides no advantage over mating with one partner, and therefore females exhibit no difference in evening activity between polygamous and monogamous individuals.[23] For males, however, mating with multiple partners increases their reproductive success by increasing the genetic diversity of their offspring.[23] This benefit of genetic diversity is an evolutionary advantage because it increases the chance that some of the offspring will have traits that increase their fitness in their environment.

The difference in evening activity between polygamous and monogamous male flies can be explained with courtship. For polygamous flies, their reproductive success increases by having offspring with multiple partners, and therefore they spend more time and energy on courting multiple females.[23] On the other hand, monogamous flies only court one female, and expend less energy doing so.[23] While it requires more energy for male flies to court multiple females, the overall reproductive benefits it produces has kept polygamy as the preferred sexual choice.[23]

It has been shown that the mechanism that affects courtship behavior in Drosophila is controlled by the oscillator neurons DN1s and LNDs.[24] Oscillation of the DN1 neurons was found to be effected by socio-sexual interactions, and is connected to mating-related decrease of evening activity.[24]

D. melanogaster was among the first organisms used for genetic analysis, and today it is one of the most widely used and genetically best-known of all eukaryotic organisms. All organisms use common genetic systems; therefore, comprehending processes such as transcription and replication in fruit flies helps in understanding these processes in other eukaryotes, including humans.[25]

Thomas Hunt Morgan began using fruit flies in experimental studies of heredity at Columbia University in 1910 in a laboratory known as the Fly Room. The Fly Room was cramped with eight desks, each occupied by students and their experiments. They started off experiments using milk bottles to rear the fruit flies and handheld lenses for observing their traits. The lenses were later replaced by microscopes, which enhanced their observations. Morgan and his students eventually elucidated many basic principles of heredity, including sex-linked inheritance, epistasis, multiple alleles, and gene mapping.[25]

D. melanogaster is one of the most studied organisms in biological research, particularly in genetics and developmental biology. The several reasons include:

Genetic markers are commonly used in Drosophila research, for example within balancer chromosomes or P-element inserts, and most phenotypes are easily identifiable either with the naked eye or under a microscope. In the list of example common markers below, the allele symbol is followed by the name of the gene affected and a description of its phenotype. (Note: Recessive alleles are in lower case, while dominant alleles are capitalised.)

Drosophila genes are traditionally named after the phenotype they cause when mutated. For example, the absence of a particular gene in Drosophila will result in a mutant embryo that does not develop a heart. Scientists have thus called this gene tinman, named after the Oz character of the same name.[27] This system of nomenclature results in a wider range of gene names than in other organisms.

The genome of D. melanogaster (sequenced in 2000, and curated at the FlyBase database[26]) contains four pairs of chromosomes: an X/Y pair, and three autosomes labeled 2, 3, and 4. The fourth chromosome is so tiny, it is often ignored, aside from its important eyeless gene. The D. melanogaster sequenced genome of 139.5 million base pairs has been annotated[28] and contains around 15,682 genes according to Ensemble release 73. More than 60% of the genome appears to be functional non-protein-coding DNA[29] involved in gene expression control. Determination of sex in Drosophila occurs by the X:A ratio of X chromosomes to autosomes, not because of the presence of a Y chromosome as in human sex determination. Although the Y chromosome is entirely heterochromatic, it contains at least 16 genes, many of which are thought to have male-related functions.[30]

A March 2000 study by National Human Genome Research Institute comparing the fruit fly and human genome estimated that about 60% of genes are conserved between the two species.[31] About 75% of known human disease genes have a recognizable match in the genome of fruit flies,[32] and 50% of fly protein sequences have mammalian homologs. An online database called Homophila is available to search for human disease gene homologues in flies and vice versa.[33]Drosophila is being used as a genetic model for several human diseases including the neurodegenerative disorders Parkinson’s, Huntington’s, spinocerebellar ataxia and Alzheimer’s disease. The fly is also being used to study mechanisms underlying aging and oxidative stress, immunity, diabetes, and cancer, as well as drug abuse.

Embryogenesis in Drosophila has been extensively studied, as its small size, short generation time, and large brood size makes it ideal for genetic studies. It is also unique among model organisms in that cleavage occurs in a syncytium.

During oogenesis, cytoplasmic bridges called “ring canals” connect the forming oocyte to nurse cells. Nutrients and developmental control molecules move from the nurse cells into the oocyte. In the figure to the left, the forming oocyte can be seen to be covered by follicular support cells.

After fertilization of the oocyte, the early embryo (or syncytial embryo) undergoes rapid DNA replication and 13 nuclear divisions until about 5000 to 6000 nuclei accumulate in the unseparated cytoplasm of the embryo. By the end of the eighth division, most nuclei have migrated to the surface, surrounding the yolk sac (leaving behind only a few nuclei, which will become the yolk nuclei). After the 10th division, the pole cells form at the posterior end of the embryo, segregating the germ line from the syncytium. Finally, after the 13th division, cell membranes slowly invaginate, dividing the syncytium into individual somatic cells. Once this process is completed, gastrulation starts.[34]

Nuclear division in the early Drosophila embryo happens so quickly, no proper checkpoints exist, so mistakes may be made in division of the DNA. To get around this problem, the nuclei that have made a mistake detach from their centrosomes and fall into the centre of the embryo (yolk sac), which will not form part of the fly.

The gene network (transcriptional and protein interactions) governing the early development of the fruit fly embryo is one of the best understood gene networks to date, especially the patterning along the anteroposterior (AP) and dorsoventral (DV) axes (See under morphogenesis).[34]

The embryo undergoes well-characterized morphogenetic movements during gastrulation and early development, including germ-band extension, formation of several furrows, ventral invagination of the mesoderm, and posterior and anterior invagination of endoderm (gut), as well as extensive body segmentation until finally hatching from the surrounding cuticle into a first-instar larva.

During larval development, tissues known as imaginal discs grow inside the larva. Imaginal discs develop to form most structures of the adult body, such as the head, legs, wings, thorax, and genitalia. Cells of the imaginal disks are set aside during embryogenesis and continue to grow and divide during the larval stagesunlike most other cells of the larva, which have differentiated to perform specialized functions and grow without further cell division. At metamorphosis, the larva forms a pupa, inside which the larval tissues are reabsorbed and the imaginal tissues undergo extensive morphogenetic movements to form adult structures.

Drosophila flies have both X and Y chromosomes, as well as autosomes. Unlike humans, the Y chromosome does not confer maleness; rather, it encodes genes necessary for making sperm. Sex is instead determined by the ratio of X chromosomes to autosomes. Furthermore, each cell “decides” whether to be male or female independently of the rest of the organism, resulting in the occasional occurrence of gynandromorphs.

Three major genes are involved in determination of Drosophila sex. These are sex-lethal, sisterless, and deadpan. Deadpan is an autosomal gene which inhibits sex-lethal, while sisterless is carried on the X chromosome and inhibits the action of deadpan. An AAX cell has twice as much deadpan as sisterless, so sex-lethal will be inhibited, creating a male. However, an AAXX cell will produce enough sisterless to inhibit the action of deadpan, allowing the sex-lethal gene to be transcribed to create a female.

Later, control by deadpan and sisterless disappears and what becomes important is the form of the sex-lethal gene. A secondary promoter causes transcription in both males and females. Analysis of the cDNA has shown that different forms are expressed in males and females. Sex-lethal has been shown to affect the splicing of its own mRNA. In males, the third exon is included which encodes a stop codon, causing a truncated form to be produced. In the female version, the presence of sex-lethal causes this exon to be missed out; the other seven amino acids are produced as a full peptide chain, again giving a difference between males and females.[35]

Presence or absence of functional sex-lethal proteins now go on to affect the transcription of another protein known as doublesex. In the absence of sex-lethal, doublesex will have the fourth exon removed and be translated up to and including exon 6 (DSX-M[ale]), while in its presence the fourth exon which encodes a stop codon will produce a truncated version of the protein (DSX-F[emale]). DSX-F causes transcription of Yolk proteins 1 and 2 in somatic cells, which will be pumped into the oocyte on its production.

Unlike mammals, Drosophila flies only have innate immunity and lack an adaptive immune response. The D. melanogaster immune system can be divided into two responses: humoral and cell-mediated. The former is a systemic response mediated through the Toll and imd pathways, which are parallel systems for detecting microbes. The Toll pathway in Drosophila is known as the homologue of Toll-like pathways in mammals. Spatzle, a known ligand for the Toll pathway in flies, is produced in response to Gram-positive bacteria, parasites, and fungal infection. Upon infection, pro-Spatzle will be cleaved by protease SPE (Spatzle processing enzyme) to become active Spatzle, which then binds to the Toll receptor located on the cell surface (Fat body, hemocytes) and dimerise for activation of downstream NF-B signaling pathways. The imd pathway, though, is triggered by Gram-negative bacteria through soluble and surface receptors (PGRP-LE and LC, respectively). D. melanogaster has a “fat body”, which is thought to be homologous to the human liver. It is the primary secretory organ and produces antimicrobial peptides. These peptides are secreted into the hemolymph and bind infectious bacteria, killing them by forming pores in their cell walls. Years ago[when?] many drug companies wanted to purify these peptides and use them as antibiotics. Other than the fat body, hemocytes, the blood cells in Drosophila, are known as the homologue of mammalian monocyte/macrophages, possessing a significant role in immune responses. It is known from the literature that in response to immune challenge, hemocytes are able to secrete cytokines, for example Spatzle, to activate downstream signaling pathways in the fat body. However, the mechanism still remains unclear.

In 1971, Ron Konopka and Seymour Benzer published “Clock mutants of Drosophila melanogaster”, a paper describing the first mutations that affected an animal’s behavior. Wild-type flies show an activity rhythm with a frequency of about a day (24 hours). They found mutants with faster and slower rhythms, as well as broken rhythmsflies that move and rest in random spurts. Work over the following 30 years has shown that these mutations (and others like them) affect a group of genes and their products that comprise a biochemical or biological clock. This clock is found in a wide range of fly cells, but the clock-bearing cells that control activity are several dozen neurons in the fly’s central brain.

Since then, Benzer and others have used behavioral screens to isolate genes involved in vision, olfaction, audition, learning/memory, courtship, pain, and other processes, such as longevity.

The first learning and memory mutants (dunce, rutabaga, etc.) were isolated by William “Chip” Quinn while in Benzer’s lab, and were eventually shown to encode components of an intracellular signaling pathway involving cyclic AMP, protein kinase A, and a transcription factor known as CREB. These molecules were shown to be also involved in synaptic plasticity in Aplysia and mammals.[citation needed]

Male flies sing to the females during courtship using their wings to generate sound, and some of the genetics of sexual behavior have been characterized. In particular, the fruitless gene has several different splice forms, and male flies expressing female splice forms have female-like behavior and vice versa. The TRP channels nompC, nanchung, and inactive are expressed in sound-sensitive Johnston’s organ neurons and participate in the transduction of sound.[36][37]

Furthermore, Drosophila has been used in neuropharmacological research, including studies of cocaine and alcohol consumption. Models for Parkinson’s disease also exist for flies.[38]

Stereo images of the fly eye

The compound eye of the fruit fly contains 760 unit eyes or ommatidia, and are one of the most advanced among insects. Each ommatidium contains eight photoreceptor cells (R1-8), support cells, pigment cells, and a cornea. Wild-type flies have reddish pigment cells, which serve to absorb excess blue light so the fly is not blinded by ambient light.

Each photoreceptor cell consists of two main sections, the cell body and the rhabdomere. The cell body contains the nucleus, while the 100-m-long rhabdomere is made up of toothbrush-like stacks of membrane called microvilli. Each microvillus is 12 m in length and about 60 nm in diameter.[39] The membrane of the rhabdomere is packed with about 100 million rhodopsin molecules, the visual protein that absorbs light. The rest of the visual proteins are also tightly packed into the microvillar space, leaving little room for cytoplasm.

The photoreceptors in Drosophila express a variety of rhodopsin isoforms. The R1-R6 photoreceptor cells express rhodopsin1 (Rh1), which absorbs blue light (480nm). The R7 and R8 cells express a combination of either Rh3 or Rh4, which absorb UV light (345nm and 375nm), and Rh5 or Rh6, which absorb blue (437nm) and green (508nm) light, respectively. Each rhodopsin molecule consists of an opsin protein covalently linked to a carotenoid chromophore, 11-cis-3-hydroxyretinal.[40]

As in vertebrate vision, visual transduction in invertebrates occurs via a G protein-coupled pathway. However, in vertebrates, the G protein is transducin, while the G protein in invertebrates is Gq (dgq in Drosophila). When rhodopsin (Rh) absorbs a photon of light its chromophore, 11-cis-3-hydroxyretinal, is isomerized to all-trans-3-hydroxyretinal. Rh undergoes a conformational change into its active form, metarhodopsin. Metarhodopsin activates Gq, which in turn activates a phospholipase C (PLC) known as NorpA.[41]

PLC hydrolyzes phosphatidylinositol (4,5)-bisphosphate (PIP2), a phospholipid found in the cell membrane, into soluble inositol triphosphate (IP3) and diacylglycerol (DAG), which stays in the cell membrane. DAG or a derivative of DAG causes a calcium-selective ion channel known as transient receptor potential (TRP) to open and calcium and sodium flows into the cell. IP3 is thought to bind to IP3 receptors in the subrhabdomeric cisternae, an extension of the endoplasmic reticulum, and cause release of calcium, but this process does not seem to be essential for normal vision.[41]

Calcium binds to proteins such as calmodulin (CaM) and an eye-specific protein kinase C (PKC) known as InaC. These proteins interact with other proteins and have been shown to be necessary for shut off of the light response. In addition, proteins called arrestins bind metarhodopsin and prevent it from activating more Gq. A sodium-calcium exchanger known as CalX pumps the calcium out of the cell. It uses the inward sodium gradient to export calcium at a stoichiometry of 3 Na+/ 1 Ca++.[42]

TRP, InaC, and PLC form a signaling complex by binding a scaffolding protein called InaD. InaD contains five binding domains called PDZ domain proteins, which specifically bind the C termini of target proteins. Disruption of the complex by mutations in either the PDZ domains or the target proteins reduces the efficiency of signaling. For example, disruption of the interaction between InaC, the protein kinase C, and InaD results in a delay in inactivation of the light response.

Unlike vertebrate metarhodopsin, invertebrate metarhodopsin can be converted back into rhodopsin by absorbing a photon of orange light (580nm).

About two-thirds of the Drosophila brain is dedicated to visual processing.[43] Although the spatial resolution of their vision is significantly worse than that of humans, their temporal resolution is around 10 times better.

The wings of a fly are capable of beating up to 220 times per second.[citation needed] Flies fly via straight sequences of movement interspersed by rapid turns called saccades.[44] During these turns, a fly is able to rotate 90 in less than 50 milliseconds.[44]

Characteristics of Drosophila flight may be dominated by the viscosity of the air, rather than the inertia of the fly body, but the opposite case with inertia as the dominant force may occur.[44] However, subsequent work showed that while the viscous effects on the insect body during flight may be negligible, the aerodynamic forces on the wings themselves actually cause fruit flies’ turns to be damped viscously.[45]

Drosophila is commonly considered a pest due to its tendency to infest habitations and establishments where fruit is found; the flies may collect in homes, restaurants, stores, and other locations.[3] Removal of an infestation can be difficult, as larvae may continue to hatch in nearby fruit even as the adult population is eliminated.

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World Stem Cell Summit

Cellular Dynamics

Cellular Dynamics International (CDI), a FUJIFILM company, is a leading developer and manufacturer of human cells used in drug discovery, toxicity testing, stem cell banking, and cell therapy development. The Company partners with innovators from around the world to combine biologically relevant human cells with the newest technologies to drive advancements in medicine and healthier living. CDIs technology offers the potential to create induced pluripotent stem cells (iPSCs) from anyone, starting with a standard blood draw, and followed by the powerful capability to develop into virtually any cell type in the human body. Our proprietary manufacturing system produces billions of cells daily, resulting in inventoried iCell products and donor-specific MyCell Products in the quantity, quality, purity, and reproducibility required for drug and cell therapy development. Founded in 2004 by Dr. James Thomson, a pioneer in human pluripotent stem cell research, Cellular Dynamics is based in Madison, Wisconsin, with a second facility in Novato, California. For more information, please visit, and follow us on Twitter @CellDynamics. FUJIFILM Holdings Corporation, Tokyo, Japan brings continuous innovation and leading-edge products to a broad spectrum of industries, including: healthcare, with medical systems, pharmaceuticals and cosmetics; graphic systems; highly functional materials, such as flat panel display materials; optical devices, such as broadcast and cinema lenses; digital imaging; and document products. These are based on a vast portfolio of chemical, mechanical, optical, electronic, software and production technologies. In the year ended March 31, 2015, the company had global revenues of $20.8 billion, at an exchange rate of 120 yen to the dollar. Fujifilm is committed to environmental stewardship and good corporate citizenship. For more information, please visit:

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Cancer Genetics Risk Assessment and Counseling (PDQ …


[Note: Many of the medical and scientific terms used in this summary are found in the NCI Dictionary of Genetics Terms. When a linked term is clicked, the definition will appear in a separate window.]

[Note: A concerted effort is being made within the genetics community to shift terminology used to describe genetic variation. The shift is to use the term variant rather than the term mutation to describe a difference that exists between the person or group being studied and the reference sequence. Variants can then be further classified as benign (harmless), likely benign, of uncertain significance, likely pathogenic, or pathogenic (disease causing). Throughout this summary, we will use the term pathogenic variant to describe a disease-causing mutation. Refer to the Cancer Genetics Overview summary for more information about variant classification.]

This summary describes current approaches to assessing and counseling people about their chance of having an inherited susceptibility to cancer. Genetic counseling is defined by the National Society of Genetic Counselors as the process of helping people understand and adapt to the medical, psychological, and familial implications of genetic contributions to disease. Several reviews present overviews of the cancer risk assessment, counseling, and genetic testing process.[1,2]

Individuals are considered to be candidates for cancer risk assessment if they have a personal and/or family history (maternal or paternal lineage) with features suggestive of hereditary cancer.[1] These features vary by type of cancer and specific hereditary syndrome. Criteria have been published to help identify individuals who may benefit from genetic counseling.[1,3] The PDQ cancer genetics information summaries on breast, ovarian, endometrial, colorectal, prostate, kidney, and skin cancers and endocrine and neuroendocrine neoplasias describe the clinical features of hereditary syndromes associated with these conditions.

The following are features that suggest hereditary cancer:

As part of the process of genetic education and counseling, genetic testing may be considered when the following factors are present:

It is important that individuals who are candidates for genetic testing undergo genetic education and counseling before testing to facilitate informed decision making and adaptation to the risk or condition.[1] Genetic education and counseling allows individuals to consider the various medical uncertainties, diagnosis, or medical management based on varied test results, and the risks, benefits, and limitations of genetic testing.

Comprehensive cancer risk assessment is a consultative service that includes clinical assessment, genetic testing when appropriate, and risk management recommendations delivered in the context of one or more genetic counseling sessions. Pretest genetic counseling is an important part of the risk assessment process and helps patients understand their genetic testing options and potential outcomes. Posttest genetic counseling helps patients understand their test results, including the medical implications for themselves and their relatives.

Several professional organizations emphasize the importance of genetic counseling in the cancer risk assessment and genetic testing process. Examples of these organizations include the following:

A list of organizations that have published clinical practices guidelines related to genetic counseling, risk assessment, genetic testing, and/or management for hereditary breast and ovarian cancers is available in the PDQ summary on Genetics of Breast and Gynecologic Cancers.

Genetic counseling informs the consultand about potential cancer risks and the benefits and limitations of genetic testing and offers an opportunity to consider the potential medical, psychological, familial, and social implications of genetic information.[8,15] Descriptions of genetic counseling and the specialized practice of cancer risk assessment counseling are detailed below.

Genetic counseling has been defined by the American Society of Human Genetics as a communication process that deals with the human problems associated with the occurrence, or risk of occurrence, of a genetic disorder in a family.” The process involves an attempt by one or more appropriately trained persons to help the individual or family do the following:

In 2006, the National Society of Genetic Counselors further refined the definition of genetic counseling to include the process of helping people understand and adapt to the medical, psychological, and familial implications of genetic contributions to disease, including integration of the following:

Central to the philosophy and practice of genetic counseling are the principles of voluntary utilization of services, informed decision making, attention to psychosocial and affective dimensions of coping with genetic risk, and protection of patient confidentiality and privacy. This is facilitated through a combination of rapport building and information gathering; establishing or verifying diagnoses; risk assessment and calculation of quantitative occurrence/recurrence risks; education and informed consent processes; psychosocial assessment, support, and counseling appropriate to a familys culture and ethnicity; and other relevant background characteristics.[17,18] The psychosocial assessment is especially important in the genetic counseling process because individuals most vulnerable to adverse effects of genetic information may include those who have had difficulty dealing with stressful life events in the past.[19] Variables that may influence psychosocial adjustment to genetic information include individual and familial factors; cultural factors; and health system factors such as the type of test, disease status, and risk information.[19] Findings from a psychosocial assessment can be used to help guide the direction of the counseling session.[9] An important objective of genetic counseling is to provide an opportunity for shared decision making when the medical benefits of one course of action are not demonstrated to be superior to another. The relationship between the availability of effective medical treatment for carriers of pathogenic variants and the clinical validity of a given test affects the degree to which personal choice or physician recommendation is supported in counseling at-risk individuals.[20] Uptake of genetic counseling services among those referred varies based on the cancer syndrome and the clinical setting. Efforts to decrease barriers to service utilization are ongoing (e.g., a patient navigator telephone call may increase utilization of these services).[21] Readers interested in the nature and history of genetic counseling are referred to a number of comprehensive reviews.[22-27]

Cancer risk assessment counseling has emerged as a specialized practice that requires knowledge of genetics, oncology, and individual and family counseling skills that may be provided by health care providers with this interdisciplinary training.[28] Some centers providing cancer risk assessment services involve a multidisciplinary team, which may include a genetic counselor; a genetics advanced practice nurse; a medical geneticist or a physician, such as an oncologist, surgeon, or internist; and a mental health professional. The Cancer Genetics Services Directory provides a partial list of individuals involved in cancer risk assessment, genetic counseling, testing, and other related services and is available on the National Cancer Institute’s website.

The need for advanced professional training in cancer genetics for genetics counselors, physicians, nurses, laboratory technicians, and others has been widely reported.[29-32] Despite these identified needs, the evidence indicates that competency in genetics and genomics remains limited across all health care disciplines, with the exception of genetic specialists.[33] Deficits in the following have been identified: (1) knowledge about hereditary cancer syndromes [34] and risk-appropriate management strategies;[35] (2) provision of genetic counseling services;[35] (3) documentation and use of personal and family cancer history to identify and refer patients at increased risk of hereditary cancer syndromes;[36-39] and (4) knowledge about genetic nondiscrimination laws.[36,40] (Refer to the table on Health Professional Practice and Genetic Education Information in the PDQ Cancer Genetics Overview summary for more information.)

The National Coalition for Health Professional Education in Genetics (whose work was transitioned to The Jackson Laboratory in 2013) has published core competencies for all health professionals. Building on this work, individual health professions, such as physicians,[32] nurses,[41,42] physician assistants,[43] pharmacists,[44] and genetic counselors,[45] have developed and published core competencies specific to their profession. A number of other organizations have also published professional guidelines, scopes, and standards of practice.

Traditionally, genetic counseling services have been delivered using individualized in-person appointments. However, other methodologies are being explored, including group sessions, telephone counseling, and telemedicine by videoconferencing.[46-53] Additionally, computer programs and websites designed to provide genetics education can be successful adjuncts to personal genetic counseling services in a computer-literate population.[54-58]

Some studies of patient satisfaction with cancer genetic counseling services have been published. For example, one survey of individuals who participated in a cancer genetics program in its inaugural year reported that the clinical services met the needs and expectations of most people.[59] Patients reported that the best parts of the experience were simply having a chance to talk to someone about cancer concerns, having personalized summary letters and family pedigrees, learning that cancer risk was lower than expected, or realizing that one had been justified in suspecting the inheritance of cancer in ones family.

Several studies have since shown that the majority of individuals are satisfied with their genetic counseling experience.[60-63] However, one study of 61 women participating in a BRCA1/2 genetic testing program found that satisfaction with genetic counseling was influenced by psychological variables including optimism, family functioning, and general and cancer-specific distress.[64]

A meta-analysis of several controlled studies showed that outcomes of genetic counseling included improvement in cancer genetic knowledge (pooled short-term difference, 0.70 U; 95% confidence interval, 0.151.26 U). Overall, no long-term increases in general anxiety, cancer-specific worry, distress, or depression were detected as a consequence of genetic counseling. However, the impact of genetic counseling on risk perception is less clear, with some studies reporting no change in risk perception while others report significant differences before and after counseling.[65]

This section provides an overview of critical elements in the cancer risk assessment process.

A number of professional guidelines on the elements of cancer genetics risk assessment and counseling are available.[1-4] Except where noted, the discussion below is based on these guidelines.

The cancer risk assessment and counseling process, which may vary among providers, requires one or more consultative sessions and generally includes the following:

At the outset of the initial counseling session, eliciting and addressing the consultand’s perceptions and concerns about cancer and his or her expectations of the risk assessment process helps to engage the consultand in the session. This also helps inform the provider about practical or psychosocial issues and guides the focus of counseling and strategies for risk assessment.

The counseling process that takes place as part of a cancer risk assessment can identify factors that contribute to the consultand’s perception of cancer risk and motivations to seek cancer risk assessment and genetic testing. It can also identify potential psychological issues that may need to be addressed during or beyond the session. Information collected before and/or during the session may include the following:

Either alone or in consultation with a mental health provider, health care providers offering cancer risk counseling attempt to assess whether the individual’s expectations of counseling are realistic and whether there are factors suggesting risk of adverse psychological outcomes after disclosure of risk and/or genetic status. In some cases, referral for psychotherapeutic treatment may be recommended prior to, or in lieu of, testing.[5]

Concepts of personal cancer risk, genetics, and the relationship between the two can be complex and can be difficult for patients to understand. A number of factors influence a persons concept of his or her risk, which may not be congruent with evidence-based quantitative calculations. These factors include:

A thorough understanding of these issues can greatly inform genetic education and counseling. These factors influence the processing of risk information and subsequent health behaviors.[9]

The communication of risk involves the delivery of quantitative information regarding what the data indicate about the likelihood of developing illness given various preventive actions. More broadly, however, risk communication is an interactive process regarding the individuals knowledge, beliefs, emotions, and behaviors associated with risk and the risk message conveyed. Accordingly, the goal of risk communication may be to impact the individuals knowledge of risk factors, risk likelihoods, potential consequences of risk, and the benefits and drawbacks of preventive actions.

Even before the provision of risk information, the provider may anticipate that the individual already has some sense of his or her own risk of cancer. The individual may have derived this information from multiple sources, including physicians, family members, and the media.[10] This information may be more salient or emotional if a family member has recently died from cancer or if there is a new family diagnosis.[11,12] Additionally, individuals may have beliefs about how genetic susceptibility works in their family.[13,14] For example, in a family where only females have been affected with an autosomal dominant cancer susceptibility syndrome thus far, it may be difficult to convince the consultand that her sons have a 50% risk of inheriting the disease-related pathogenic variant. The social-ecological context through which risk beliefs develop and are maintained are important as potential moderators of individuals receptivity to the cancer risk communication process and also represent the context in which individuals will return to continue ongoing decision making about how to manage their risk.[15,16] As such, individuals beliefs, and the social context of risk, are important to discuss in education and genetic risk counseling.

Perceived risk can play an important role in an individuals decision to participate in counseling,[17] despite the fact that perceived risk often varies substantially from statistical risk estimates.[18-20]

Consideration of the consultand’s personal health history is essential in cancer risk assessment, regardless of whether the individual has a personal history of cancer. Important information to obtain about the consultand’s health history includes the following:

For consultands with a history of cancer, additional information collected includes the following:

In some cases, a physical exam is conducted by a qualified medical professional to determine whether the individual has physical findings suggestive of a hereditary cancer predisposition syndrome or to rule out evidence of an existing malignancy. For example, a medical professional may look for the sebaceous adenomas seen in Muir-Torre syndrome, measure the head circumference or perform a skin exam to rule out benign cutaneous features associated with Cowden syndrome, or perform a clinical breast and axillary lymph node exam on a woman undergoing a breast cancer risk assessment.

The family history is an essential tool for cancer risk assessment. The family history can be obtained via interview or written self-report; both were found to result in equivalent information in a study that utilized a sample (N = 104) that varied widely in educational attainment.[22] A nine-question family history screening tool has been shown to identify individuals at increased risk of common health conditions, including cancer, who warrant a more detailed family history (receiver operating characteristic, 84.6% [range, 81.2%88.1%]; sensitivity, 95% [range, 92%98%]; specificity, 54% [range, 48%60%]).[23] Studies suggest that paper-based family history questionnaires completed before the appointment provide accurate family history information [24] and that the use of these questionnaires is an acceptable and understandable family history collection method.[25] However, questionnaire-based assessments may lead to some underreporting of family history; therefore, a follow-up interview to confirm the reported information and to capture all relevant family history information may be required.[26] Routine chart reviews (e.g., via electronic medical records) may be worthwhile to maximize the identification of appropriate candidates for genetic counseling referral. In a single nonacademic institution, systematic chart review by a genetic counselor increased the number of referrals for genetics consultation.[27] The most significant improvement was in ovarian cancer referrals. In conjunction with other efforts to collect and review family history, the performance of routine chart reviews may help identify gaps in existing referral patterns. Additionally, collecting family history from multiple relatives in a single family has been shown to increase the number of reported family members with cancer, compared with family history information provided by a single family member.[28]

Details of the family health history are best summarized in the form of a family tree, or pedigree. The pedigree, a standardized graphic representation of family relationships, facilitates identification of patterns of disease transmission, recognition of the clinical characteristics associated with specific hereditary cancer syndromes, and determination of the best strategies and tools for risk assessment.[29,30] Factors suggesting inherited cancer risk in a family are described below.

Both multimedia-based (e.g., Internet) and print-based (e.g., family history questionnaires) tools are currently available to gather information about family history. In the United States, many are written at reading grade levels above 8th grade, which may reduce their effectiveness in gathering accurate family history information. On average, print-based tools have been found to be written at lower reading grade levels than multimedia-based tools.[31]

Standards of pedigree nomenclature have been established.[29,30] Refer to Figure 1 for common pedigree symbols.

Figure 1. Standard pedigree nomenclature. Common symbols are used to draw a pedigree (family tree). A pedigree shows relationships between family members and patterns of inheritance for certain traits and diseases.

Documentation of a family cancer history typically includes the following:

A three-generation family history includes the following:

For any relative with cancer, collect the following information:[33]

For relatives not affected with cancer, collect the following information:

The accuracy of the family history has a direct bearing on determining the differential diagnoses, selecting appropriate testing, interpreting results of the genetic tests, refining individual cancer risk estimates, and outlining screening and risk reduction recommendations. In a telephone survey of 1,019 individuals, only 6% did not know whether a first-degree relative had cancer; this increased to 8.5% for second-degree relatives.[34] However, people often have incomplete or inaccurate information about the cancer history in their family.[30,33,35-41] Patient education has been shown to improve the completeness of family history collection and may lead to more-accurate risk stratification, referrals for genetic counseling, and changes to management recommendations.[42] Confirming the primary site of cancers in the family that will affect the calculation of hereditary predisposition probabilities and/or estimation of empiric cancer risks may be important, especially if decisions about treatments such as risk-reducing surgery will be based on this family history.[37,43]

A population-based survey of 2,605 first- and second-degree relatives confirmed proband reports of cancer diagnoses and found that the accuracy of reported cancer diagnoses in relatives was low to moderate, while reports of no history of cancer were accurate.[39] Accuracy varies by cancer site and degree of relatedness.[39,44,45] Reporting of cancer family histories may be most accurate for breast cancer [39,45] and less accurate for gynecologic malignancies [39,45] and colon cancer.[39] Self-reported family histories may contain errors and, in rare instances, could be fictitious.[37,43,45] The most reliable documentation of cancer histology is the pathology report. Verification of cancers can also be made through other medical records, tumor registries, or death certificates. A U.K. study illustrates the importance of verification of the cancer family history in individuals with a family history of breast cancer (n = 2,278) and colon cancer (n = 1,184).[41] Changes in genetic risk assignment (reassignment) from baseline to final time points (e.g., low risk to high risk) warranting management changes were reported in nearly 30% of families with colorectal cancer and 20% of families with breast cancer. Verification of reported cancer diagnoses in this cohort revealed a lower overall degree of consistency between reported and confirmed diagnoses than in other studies.[37,46]

It is also important to consider limited, missing, or questionable information when reviewing a pedigree for cancer risk assessment. It is more difficult to identify features of hereditary disease in families with a truncated family structure due to loss of contact with relatives, small family size, or deaths at an early age from unrelated conditions. When there are few family members of the at-risk gender when considering a particular syndrome with primarily male or female specific disease manifestations, the family history may be difficult to assess (e.g., few female members in a family at risk of hereditary breast and ovarian cancer syndrome). In addition, information collected on risk-reducing surgical procedures, such as oophorectomy, could significantly change prior probability estimation and the constellation of cancers observed in a family.[47] Other factors to clarify and document whenever possible are adoptions, use of donor egg or sperm, consanguinity, and uncertain paternity.

Additionally, family histories are dynamic. The occurrence of additional cancers may alter the likelihood of a hereditary predisposition to cancer, and consideration of differential diagnoses or empiric cancer risk estimates may change if additional cancers arise in the family. Furthermore, changes in the cancer family history over time may alter recommendations for earlier or more intense cancer screening. A descriptive study that examined baseline and follow-up family history data from a U.S. population-based cancer registry reported that family history of breast cancer or colorectal cancer becomes increasingly relevant in early adulthood and changes significantly from age 30 years to age 50 years.[48] Therefore, it is important to advise the consultand to take note of, confirm, and report cancer diagnoses or other pertinent family health history that occurs after completion of the initial risk assessment process. This is especially important if genetic testing was not performed or was uninformative.

Finally, the process of taking the family history has a psychosocial dimension. Discussing and documenting discrete aspects of family relationships and health brings the family into the session symbolically, even when a single person is being counseled. Problems that may be encountered in eliciting a family history and constructing a pedigree include difficulty contacting relatives with whom one has little or no relationship, differing views between family members about the value of genetic information, resistance to discussion of cancer and cancer-related illness, unanticipated discovery of previously unknown medical or family information, and coercion of one relative by another regarding testing decisions. In addition, unexpected emotional distress may be experienced by the consultand in the process of gathering family history information.

After an individuals personal and family cancer histories have been collected, several factors could warrant referral to a genetics professional for evaluation of hereditary cancer susceptibility syndromes. The American College of Medical Genetics and Genomics and the National Society of Genetic Counselors have published a comprehensive set of personal and family history criteria to guide the identification of at-risk individuals and appropriate referral for cancer genetic risk consultation.[49] These practice guidelines take into account tumor types or other features and related criteria that would indicate a need for a genetics referral. The authors state that the guidelines are intended to maximize appropriate referral of at-risk individuals for cancer genetic consultation but are not meant to provide genetic testing or treatment recommendations.

Because a family history of cancer is one of the important predictors of cancer risk, analysis of the pedigree constitutes an important aspect of risk assessment. This analysis might be thought of as a series of the following questions:

The following sections relate to the way that each of these questions might be addressed:

The clues to a hereditary syndrome are based on pedigree analysis and physical findings. The index of suspicion is raised by the following:

Clinical characteristics associated with distinctive risk ranges for different cancer genetic syndromes are summarized in the second edition of the Concise Handbook of Familial Cancer Susceptibility Syndromes.[50]

Hundreds of inherited conditions are associated with an increased risk of cancer. These have been summarized in texts [51-53] and a concise review.[50] Diagnostic criteria for different hereditary syndromes incorporate different features from the list above, depending on the original purpose of defining the syndrome (e.g., for gene mapping, genotype -phenotype studies, epidemiological investigations, population screening, or clinical service). Thus, a syndrome such as Lynch syndrome (also called hereditary nonpolyposis colorectal cancer [HNPCC]) can be defined for research purposes by the Amsterdam criteria as having three related individuals with colorectal cancer, with one person being a first-degree relative of the other two; spanning two generations; and including one person who was younger than age 50 years at cancer diagnosis, better known as the 3-2-1 rule. These criteria have limitations in the clinical setting, however, in that they ignore endometrial and other extracolonic tumors known to be important features of Lynch syndrome. Revised published criteria that consider extracolonic cancers of Lynch syndrome have been subsequently developed and include the Amsterdam criteria II and the revised Bethesda guidelines.

Other factors may complicate recognition of basic inheritance patterns or represent different types of disease etiology. These factors include the following:

The mode of inheritance refers to the way that genetic traits are transmitted in the family. Mendels laws of inheritance posit that genetic factors are transmitted from parents to offspring as discrete units known as genes that are inherited independently from each other and are passed on from an older generation to the following generation. The most common forms of Mendelian inheritance are autosomal dominant, autosomal recessive, and X-linked. Non-Mendelian forms of inheritance include chromosomal, complex, and mitochondrial. Researchers have learned from cancer and other inherited diseases that even Mendelian inheritance is modified by environmental and other genetic factors and that there are variations in the ways that the laws of inheritance work.[54-56]

Most commonly, Mendelian inheritance is established by a combination of clinical diagnosis with a compatible, but not in itself conclusive, pedigree pattern.[57] Below is a list of inheritance patterns with clues to their recognition in the pedigree, followed by a list of situations that may complicate pedigree interpretation.

Autosomal dominant

Autosomal recessive




Susceptibility or resistance shows a more or less normal distribution in the population. Most people have an intermediate susceptibility, with those at the tails of the distribution curve having unusually low or unusually high susceptibility. Affected individuals are presumably those who are past a point of threshold for being affected due to their particular combination of risk factors. Outside of the few known Mendelian syndromes that predispose to a high incidence of specific cancer, most cancers are complex in etiology.

Clustering of cancer among relatives is common, but teasing out the underlying causes when there is no clear pattern is more difficult. With many common malignancies, such as lung cancer, an excess of cancers in relatives can be seen. These familial aggregations are seen as being due to combinations of exposures to known carcinogens, such as tobacco smoke, and to pathogenic variants in high penetrance genes or alterations in genes with low penetrance that affect the metabolism of the carcinogens in question.[58]

The general practitioner is likely to encounter some families with a strong genetic predisposition to cancer and the recognition of cancer susceptibility may have dramatic consequences for a given individual’s health and management. Although pathogenic variants in major cancer susceptibility genes lead to recognizable Mendelian inheritance patterns, they are uncommon. Nonetheless, cancer susceptibility genes are estimated to contribute to the occurrence of organ-specific cancers from less than 1% to up to 15%.[59] Pathogenic variants in these genes confer high relative risk and high absolute risk. The attributable risk is low, however, because they are so rare.

In contrast, scientists now know of polymorphisms or alterations in deoxyribonucleic acid that are very common in the general population. Each polymorphism may confer low relative and absolute risks, but collectively they may account for high attributable risk because they are so common. Development of clinically significant disease in the presence of certain genetic polymorphisms may be highly dependent on environmental exposure to a potent carcinogen. People carrying polymorphisms associated with weak disease susceptibility may constitute a target group for whom avoidance of carcinogen exposure may be highly useful in preventing full-blown disease from occurring.

For more information about specific low-penetrance genes, please refer to the summaries on genetics of specific types of cancer.

Complex inheritance might be considered in a pedigree showing the following:

These probabilities vary by syndrome, family, gene, and pathogenic variant, with different variants in the same gene sometimes conferring different cancer risks, or the same variant being associated with different clinical manifestations in different families. These phenomena relate to issues such as penetrance and expressivity discussed elsewhere.

A positive family history may sometimes provide risk information in the absence of a specific genetically determined cancer syndrome. For example, the risk associated with having a single affected relative with breast or colorectal cancer can be estimated from data derived from epidemiologic and family studies. Examples of empiric risk estimates of this kind are provided in the PDQ summaries on Genetics of Breast and Gynecologic Cancers and Genetics of Colorectal Cancer.

The overarching goal of cancer risk assessment is to individualize cancer risk management recommendations based on personalized risk. Methods to calculate risk utilize health history information and risk factor and family history data often in combination with emerging biologic and genetic/genomic evidence to establish predictions.[60] Multiple methodologies are used to calculate risk, including statistical models, prevalence data from specific populations, penetrance data when a documented pathogenic variant has been identified in a family, Mendelian inheritance, and Bayesian analysis. All models have distinct capabilities, weaknesses, and limitations based on the methodology, sample size, and/or population used to create the model. Methods to individually quantify risk encompass two primary areas: the probability of harboring a pathogenic variant in a cancer susceptibility gene and the risk of developing a specific form of cancer.[60]

The decision to offer genetic testing for cancer susceptibility is complex and can be aided in part by objectively assessing an individual’s and/or family’s probability of harboring a pathogenic variant.[61] Predicting the probability of harboring a pathogenic variant in a cancer susceptibility gene can be done using several strategies, including empiric data, statistical models, population prevalence data, Mendels laws, Bayesian analysis, and specific health information, such as tumor-specific features.[61,62] All of these methods are gene specific or cancer-syndrome specific and are employed only after a thorough assessment has been completed and genetic differential diagnoses have been established.

If a gene or hereditary cancer syndrome is suspected, models specific to that disorder can be used to determine whether genetic testing may be informative. (Refer to the PDQ summaries on the Genetics of Breast and Gynecologic Cancers; Genetics of Colorectal Cancer; or the Genetics of Skin Cancer for more information about cancer syndrome-specific probability models.) The key to using specific models or prevalence data is to apply the model or statistics only in the population best suited for its use. For instance, a model or prevalence data derived from a population study of individuals older than 35 years may not accurately be applied in a population aged 35 years and younger. Care must be taken when interpreting the data obtained from various risk models because they differ with regard to what is actually being estimated. Some models estimate the risk of a pathogenic variant being present in the family; others estimate the risk of a pathogenic variant being present in the individual being counseled. Some models estimate the risk of specific cancers developing in an individual, while others estimate more than one of the data above. (Refer to NCI’s Risk Prediction Models website or the disease-specific PDQ cancer genetics summaries for more information about specific cancer risk prediction and pathogenic variant probability models.) Other important considerations include critical family constructs, which can significantly impact model reliability, such as small family size or male-dominated families when the cancer risks are predominately female in origin, adoption, and early deaths from other causes.[62,63] In addition, most models provide gene and/or syndrome-specific probabilities but do not account for the possibility that the personal and/or family history of cancer may be conferred by an as-yet-unidentified cancer susceptibility gene.[64] In the absence of a documented pathogenic variant in the family, critical assessment of the personal and family history is essential in determining the usefulness and limitations of probability estimates used to aid in the decisions regarding indications for genetic testing.[61,62,64]

When a pathogenic variant has been identified in a family and a test report documents that finding, prior probabilities can be ascertained with a greater degree of reliability. In this setting, probabilities can be calculated based on the pattern of inheritance associated with the gene in which the pathogenic variant has been identified. In addition, critical to the application of Mendelian inheritance is the consideration of integrating Bayes Theorem, which incorporates other variables, such as current age, into the calculation for a more accurate posterior probability.[1,65] This is especially useful in individuals who have lived to be older than the age at which cancer is likely to develop based on the pathogenic variant identified in their family and therefore have a lower likelihood of harboring the family pathogenic variant when compared with the probability based on their relationship to the carrier in the family.

Even in the case of a documented pathogenic variant on one side of the family, careful assessment and evaluation of the individuals personal and family history of cancer is essential to rule out cancer risk or suspicion of a cancer susceptibility gene pathogenic variant on the other side of the family (maternal or paternal, as applicable).[66] Segregation of more than one pathogenic variant in a family is possible (e.g., in circumstances in which a cancer syndrome has founder pathogenic variants associated with families of particular ancestral origin).

Unlike pathogenic variant probability models that predict the likelihood that a given personal and/or family history of cancer could be associated with a pathogenic variant in a specific gene(s), other methods and models can be used to estimate the risk of developing cancer over time. Similar to pathogenic variant probability assessments, cancer risk calculations are also complex and necessitate a detailed health history and family history. In the presence of a documented pathogenic variant, cancer risk estimates can be derived from peer-reviewed penetrance data.[1] Penetrance data are constantly being refined and many genetic variants have variable penetrance because other variables may impact the absolute risk of cancer in any given patient. Modifiers of cancer risk in carriers of pathogenic variants include the variant’s effect on the function of the gene/protein (e.g., variant type and position), the contributions of modifier genes, and personal and environmental factors (e.g., the impact of bilateral salpingo-oophorectomy performed for other indications in a woman who harbors a BRCA pathogenic variant).[67] When there is evidence of an inherited susceptibility to cancer but genetic testing has not been performed, analysis of the pedigree can be used to estimate cancer risk. This type of calculation uses the probability the individual harbors a genetic variant and variant-specific penetrance data to calculate cancer risk.[1]

In the absence of evidence of a hereditary cancer syndrome, several methods can be utilized to estimate cancer risk. Relative risk data from studies of specific risk factors provide ratios of observed versus expected cancers associated with a given risk factor. However, utilizing relative risk data for individualized risk assessment can have significant limitations: relative risk calculations will differ based on the type of control group and other study-associated biases, and comparability across studies can vary widely.[65] In addition, relative risks are lifetime ratios and do not provide age-specific calculations, nor can the relative risk be multiplied by population risk to provide an individual’s risk estimate.[65,68]

In spite of these limitations, disease-specific cumulative risk estimates are most often employed in clinical settings. These estimates usually provide risk for a given time interval and can be anchored to cumulative risks of other health conditions in a given population (e.g., the 5-year risk by the Gail model).[65,68] Cumulative risk models have limitations that may underestimate or overestimate risk. For example, the Gail model excludes paternal family histories of breast cancer.[62] Furthermore, many of these models were constructed from data derived from predominately Caucasian populations and may have limited validity when used to estimate risk in other ethnicities.[69]

Cumulative risk estimates are best used when evidence of other underlying significant risk factors have been ruled out. Careful evaluation of an individual’s personal health and family history can identify other confounding risk factors that may outweigh a risk estimate derived from a cumulative risk model. For example, a woman with a prior biopsy showing lobular carcinoma in situ (LCIS) whose mother was diagnosed with breast cancer at age 65 years has a greater lifetime risk from her history of LCIS than her cumulative lifetime risk of breast cancer based on one first-degree relative.[70,71] In this circumstance, recommendations for cancer risk management would be based on the risk associated with her LCIS. Unfortunately, there is no reliable method for combining all of an individual’s relevant risk factors for an accurate absolute cancer risk estimate, nor are individual risk factors additive.

In summary, careful ascertainment and review of personal health and cancer family history are essential adjuncts to the use of prior probability models and cancer risk assessment models to assure that critical elements influencing risk calculations are considered.[61] Influencing factors include the following:

A number of investigators are developing health care provider decision support tools such as the Genetic Risk Assessment on the Internet with Decision Support (GRAIDS),[72] but at this time, clinical judgment remains a key component of any prior probability or absolute cancer risk estimation.[61]

Specific clinical programs for risk management may be offered to persons with an increased genetic risk of cancer. These programs may differ from those offered to persons of average risk in several ways: screening may be initiated at an earlier age or involve shorter screening intervals; screening strategies not in routine use, such as screening for ovarian cancer, may be offered; and interventions to reduce cancer risk, such as risk-reducing surgery, may be offered. Current recommendations are summarized in the PDQ summaries addressing the genetics of specific cancers.

The goal of genetic education and counseling is to help individuals understand their personal risk status, their options for cancer risk management, and to explore feelings regarding their personal risk status. Counseling focuses on obtaining and giving information, promoting autonomous decision making, and facilitating informed consent if genetic testing is pursued.

Optimally, education and counseling about cancer risk includes providing the following information:

When a clinically valid genetic test is available, education and counseling for genetic testing typically includes the following:

If a second session is held to disclose and interpret genetic test results, education and counseling focuses on the following:

The process of counseling may require more than one visit to address medical, genetic testing, and psychosocial support issues. Additional case-related preparation time is spent before and after the consultation sessions to obtain and review medical records, complete case documentation, seek information about differential diagnoses, identify appropriate laboratories for genetic tests, find patient support groups, research resources, and communicate with or refer to other specialists.[1]

Information about inherited risk of cancer is growing rapidly. Many of the issues discussed in a counseling session may need to be revisited as new information emerges. At the end of the counseling process, individuals are typically reminded of the possibility that future research may provide new options and/or new information on risk. Individuals may be advised to check in with the health care provider periodically to determine whether new information is sufficient to merit an additional counseling session. The obligation of health care providers to recontact individuals when new genetic testing or treatment options are available is controversial, and standards have not been established.

The usage of numerical probabilities to communicate risk may overestimate the level of risk certainty, especially when wide confidence intervals exist to the estimates or when the individual may differ in important ways from the sample on which the risk estimate was derived. Also, numbers are often inadequate for expressing gut-level or emotional aspects of risk. Finally, there are wide variations in individuals level of understanding of mathematical concepts (i.e., numeracy). For all the above reasons, conveying risk in multiple ways, both numerically and verbally, with discussion of important caveats, may be a useful strategy to increase risk comprehension. The numerical format that facilitates the best understanding is natural frequencies because frequencies include information concerning the denominator, the reference group to which the individual may refer. In general, logarithmic scales are to be avoided.[2] Additionally, important contextual risks may be included with the frequency in order to increase risk comprehension; these may include how the persons risk compares with those who do not have the risk factor in question and the risks associated with common hazards, such as being in a car accident. Additional suggestions include being consistent in risk formats (do not mix odds and percentages), using the same denominator across risk estimates, avoiding decimal points, including base rate information, and providing more explanation if the risk is less than 1%.

The communication of risk may be numerical, verbal, or visual. Use of multiple strategies may increase comprehension and retention of cancer genetic risk information.[2] Recently, use of visual risk communication strategies has increased (e.g., histograms, pie charts, and Venn diagrams). Visual depictions of risk may be very useful in avoiding problems with comprehension of numbers, but research that confirms this is lacking.[3,4] A study published in 2008 examined the use of two different visual aids to communicate breast cancer risk. Women at an increased risk of breast cancer were randomized to receive feedback via a bar graph alone or a bar graph plus a frequency diagram (i.e., highlighted human figures). Results indicate that overall, there were no differences in improved accuracy of risk perception between the two groups, but among those women who inaccurately perceived very high risk at baseline, the group receiving both visual aids showed greater improvement in accuracy.[5]

The purpose of risk counseling is to provide individuals with accurate information about their risk, help them understand and interpret their risk, assist them as they use this information to make important health care decisions, and help them make the best possible adjustment to their situation. A systematic review of 28 studies that evaluated communication interventions showed that risk communication benefits users cognitively by increasing their knowledge and understanding of risk perception and does not negatively influence affect (anxiety, cancer-related worry, and depression). Risk communication does not appear to result in a change in use of screening practices and tests. Users received the most benefit from an approach utilizing risk communication along with genetic counseling.[6,7] Perceptions of risk are affected by the manner in which risk information is presented, difficulty understanding probability and heredity,[8,9] and other psychological processes on the part of individuals and providers.[10] Risk may be communicated in many ways (e.g., with numbers, words, or graphics; alone or in relation to other risks; as the probability of having an adverse event; in relative or absolute terms; and through combinations of these methods). The way in which risk information is communicated may affect the individuals perception of the magnitude of that risk. In general, relative risk estimates (e.g., “You have a threefold increased risk of colorectal cancer”) are perceived as less informative than absolute risk (e.g., “You have a 25% risk of colorectal cancer”) [11] or risk information presented as a ratio (e.g., 1 in 4).[9] A strong preference for having BRCA1/2 pathogenic variant risk estimates expressed numerically is reported by women considering testing.[12] Individuals associate widely differing quantitative risks with qualitative descriptors of risk such as rare or common.[13] More research is needed on the best methods of communicating risk in order to help individuals develop an accurate understanding of their cancer risks.

Recent descriptive examination of the process of cancer genetic counseling has found that counseling sessions are predominantly focused on the biomedical teaching required to inform clients of their choices and to put genetic findings in perspective but that attention to psychosocial issues does not detract from teaching goals and may enhance satisfaction in clients undergoing counseling. For instance, one study of communication patterns in 167 pretest counseling sessions for BRCA1 found the sessions to have a predominantly biomedical and educational focus;[14] however, this approach was client focused, with the counselor and client contributing equally to the dialogue. These authors note that there was a marked diversity in counselor styles, both between counselors and within different sessions, for each counselor. The finding of a didactic style was corroborated by other researchers who examined observer-rated content checklists and videotape of 51 counseling sessions for breast cancer susceptibility.[15] Of note, genetic counselors seemed to rely on demographic information and breast cancer history to tailor genetic counseling sessions rather than clients self-reported expectations or psychosocial factors.[16] Concurrent provision of psychosocial and scientific information may be important in reducing worry in the context of counseling about cancer genetics topics.[17] An increasing appreciation of language choices may contribute to enhanced understanding and reduced anxiety levels in the session; for example, it was noted that patients may appreciate synonymic choices for the word mutation, such as altered gene.[18] Some authors have published recommendations for cultural tailoring of educational materials for the African-American population, such as a large flip chart, including the use of simple language and pictures, culturally identifiable images (e.g., spiritual symbols and tribal patterns), bright colors, and humor.[19]

Studies have examined novel channels to communicate genetic cancer risk information, deliver psychosocial support, and standardize the genetic counseling process for individuals at increased risk of cancer.[20-27] Much of this literature has attempted to make the genetic counseling session more efficient or to limit the need for the counselor to address basic genetic principles in the session to free up time for the clients personal and emotional concerns about his or her risk. For example, the receipt of genetic feedback for BRCA1/2 and mismatch repair gene testing by letter, rather than a face-to-face genetic counseling feedback session, has been investigated.[28] Other modalities include the development of patient assessments or checklists, CD-ROM programs, and interactive computer programs.

Patient assessments or checklists have been developed to facilitate coverage of important areas in the counseling session. One study assessed patients psychosocial needs before a hereditary cancer counseling session to determine the assessments effect on the session.[29] A total of 246 participants from two familial cancer clinics were randomly assigned to either an intervention arm in which the counselor received assessment results or a usual care control arm. Study results demonstrated that psychosocial concerns were discussed more frequently among intervention participants than among controls, without affecting session length. Moreover, cancer worry and psychological distress were significantly lower for intervention versus control participants 4 weeks after the counseling session.

A second study compared a feedback checklist completed by 197 women attending a high-risk breast clinic prior to the counseling session to convey prior genetic knowledge and misconceptions to aid the counselor in tailoring the session for that client.[22] The use of the feedback checklist led to gains in knowledge from the counseling session but did not reduce genetic counseling time, perhaps because the genetic counselor chose to spend time discussing topics such as psychosocial issues. Use of the checklist did decrease the time spent with the medical oncologist, however. The feedback checklist was compared to a CD-ROM that outlined basic genetic concepts and the benefits and limitations of testing and found that those viewing the CD-ROM spent less time with counselors and were less likely to choose to undergo genetic testing. The CD-ROM did not lead to increased knowledge of genetic concepts, as did use of the checklist.

A prospective study evaluated the effects of a CD-ROM decisional support aid for microsatellite instability (MSI) tumor testing in 239 colorectal cancer patients who met the revised Bethesda criteria but who did not meet the Amsterdam criteria.[30] The study also tested a theoretical model of factors influencing decisional conflict surrounding decisions to pursue MSI tumor testing. Within the study, half of the sample was randomly assigned to receive a brief description of MSI testing within the clinical encounter, and the other half was provided the CD-ROM decisional support aid in addition to the brief description. The CD-ROM and brief description intervention increased knowledge about MSI testing more than the brief description alone did. As a result, decisional conflict decreased because participants felt more prepared to make a decision about the test and had increased perceived benefits of MSI testing.

Other innovative strategies include educational materials and interactive computer technology. In one study, a 13-page color communication aid using a diverse format for conveying risk, including graphic representations and verbal descriptions, was developed.[23] The authors evaluated the influence of the communication aid in 27 women at high risk of a BRCA1/2 pathogenic variant and compared those who had read the aid to a comparison sample of 107 women who received standard genetic counseling. Improvements in genetic knowledge and accuracy of risk perception were documented in those who had read the aid, with no differences in anxiety or depression between groups. Personalized, interactive electronic materials have also been developed to aid in genetic education and counseling.[24,25] In one study, an interactive computer education program available prior to the genetic counseling session was compared with genetic counseling alone in women undergoing counseling for BRCA1/2 testing.[25] Use of the computer program prior to genetic counseling reduced face-time with the genetic counselor, particularly for those at lower risk of a BRCA1/2 pathogenic variant. Many of the counselors reported that their clients use of the computer program allowed them to be more efficient and to reallocate time spent in the sessions to clients unique concerns.

Videoconferencing is an innovative strategy to facilitate genetic counseling sessions with clients who cannot travel to specialized clinic settings. In 37 individuals in the United Kingdom, real-time video conferencing was compared with face-to-face counseling sessions; both methods were found to improve knowledge and reduce anxiety levels.[26] Similarly, teleconferencing sessions, in which the client and genetic specialists were able to talk with each other in real time, were used in rural Maine communities [27] in the pediatric context to convey genetic information and findings for developmental delays and were found to be comparable to in-person consultations in terms of decision-making confidence and satisfaction with the consultations. An Australian study compared the experiences of 106 women who received hereditary breast and ovarian cancer genetic counseling via videoconferencing with the experiences of 89 women who received counseling face to face. Pre- and 1-month postcounseling assessments revealed no significant differences in knowledge gains, satisfaction, cancer-specific anxiety, generalized anxiety, depression, and perceived empathy of the genetic counselor.[31]

Cancer Genetics Risk Assessment and Counseling (PDQ …

Recommendation and review posted by sam

Worrying about Anti Mullerian Hormones? | Baby Hopeful

After a massive mess up with the NHS recently (a long story) I finally managed to get my AMH (Anti-Mullerian hormones) tested last week at a private clinic.

Facts and Figures

Im sure lots of you are already too familiar with the meaning of AMH, but just incase you are unfamiliar here is a bit more information from Lane Fertility Magazine:

Anti Mullerian Hormones (AMH)

Many physicians and researchers believe that the best blood test to assess the supply of follicles in a womans ovaries is Anti-Mullerian Hormone (AMH), also known as Mullerian Inhibiting Substance (MIS). In females, this hormone is secreted by a particular group of cells in the follicles called granulosa cells. Thus, the more follicles there are in the ovaries, the greater the amount of AMH in the blood. Conversely, the fewer follicles there are in the ovaries, the lower the amount of AMH in the blood. Therefore, AMH is a reflection of the number of follicles in both ovaries. With time, as women become older, the level of AMH will naturally decrease.

This graph was interesting about how AMH levels decline with age, read more about it atFertility Associates.

The ranges used in the U.K. and U.S. should be as follows:



AMH Blood Level


AMH Blood Level




Over 3.0 ng/ml

High (often PCOS)

22 40pmol/L


Over 1.0 ng/ml


3.1 22pmol/L


0.7 0.9 ng/ml

Low Normal Range

0 3.1pmol/L

Very Low

0.3 0.6 ng/ml


Note:Reference range formerly in g/L(conversion g/L pmol/L = 7.14)

Less than 0.3 ng/ml

Very Low

I also found a great conversion chart, which was very useful as different information/labs seems to use different units of measurement.


Once again there is quite a lot of differing opinions about AMH. On my mission to source information I have found out that:

Can you imagine my surprise when I discovered that (once again) there are differing opinions and inconsistencies in the facts? Detect a hint of sarcasm? Sorry, I just couldnt resist! Once again my search for clear cut facts was in vain another grey area in this mixed up IF world.

My Results

My result came back as 8 pmol/L, in the low fertility bracket. My first reaction was to be upset (of course), but the nurse kindly explained that it isnt too bad; it is age related and lots can be done with an AMH of that level especially if I have been pregnant before. Also that it is more about quality, not quantity.

I also had a go at converting my result into ng/ml (as per the U.S. figures). I know, I know, before you say it, this is probably the wrong thing to do. They probably use different methods of testing, blah blah blah. But I couldnt resist, I was grasping at straws. And the result? 1.12 ng/ml which puts me in the normal range. Do I believe this? Im not sure, but I do like the sound of normal much more than low fertility.

So, yet again an emotional roller-coaster (albeit a small one this time) began:

What can I do about it? Nothing! Absolutely nothing! It frustrates me that time is my enemy and Im feeling the sense of urgency more than ever. But its not like Hubby and I havent been trying for the last two years what more can we do?

Your AMH Levels

Id love to hear what your AMH levels were and what you have been told about it. And Im sure there are plenty of others out there who are just as confused as I am about all this. Please comment, and lets get to the bottom of this!

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Originally posted here:
Worrying about Anti Mullerian Hormones? | Baby Hopeful

Recommendation and review posted by Bethany Smith

Physical attractiveness – Wikipedia

Venus de Milo at the Louvre has been described as a “classical vision of beauty”.[1][2][3] However, one expert claimed her “almost matronly representation” was meant to convey an “impressive appearance” rather than “ideal female beauty”.[4]

Physical attractiveness is the degree to which a person’s physical features are considered aesthetically pleasing or beautiful. The term often implies sexual attractiveness or desirability, but can also be distinct from either. There are many factors which influence one person’s attraction to another, with physical aspects being one of them. Physical attraction itself includes universal perceptions common to all human cultures, as well as aspects that are culturally and socially dependent, along with individual subjective preferences.

In many cases, humans subconsciously attribute positive characteristics, such as intelligence and honesty, to physically attractive people.[9] From research done in the United States and United Kingdom, it was found that the association between intelligence and physical attractiveness is stronger among men than among women.[10]Evolutionary psychologists have tried to answer why individuals who are more physically attractive should also, on average, be more intelligent, and have put forward the notion that both general intelligence and physical attractiveness may be indicators of underlying genetic fitness.[11] A person’s physical characteristics can signal cues to fertility and health. Attending to these factors increases reproductive success, furthering the representation of one’s genes in the population.[12]

Men, on average, tend to be attracted to women who are shorter than they are, have a youthful appearance, and exhibit features such as a symmetrical face,[13] full breasts, full lips, and a low waist-hip ratio.[14] Women, on average, tend to be attracted to men who are taller than they are, display a high degree of facial symmetry, masculine facial dimorphism, and who have broad shoulders, a relatively narrow waist, and a V-shaped torso.[15][16]

Generally, physical attractiveness can be viewed from a number of perspectives; with universal perceptions being common to all human cultures, cultural and social aspects, and individual subjective preferences. The perception of attractiveness can have a significant effect on how people are judged in terms of employment or social opportunities, friendship, sexual behavior, and marriage.[17]

Some physical features are attractive in both men and women, particularly bodily[18] and facial symmetry,[19][20][21][22] although one contrary report suggests that “absolute flawlessness” with perfect symmetry can be “disturbing”.[23] Symmetry may be evolutionarily beneficial as a sign of health because asymmetry “signals past illness or injury”.[24] One study suggested people were able to “gauge beauty at a subliminal level” by seeing only a glimpse of a picture for one-hundredth of a second.[24] Other important factors include youthfulness, skin clarity and smoothness of skin; and “vivid color” in the eyes and hair.[19] However, there are numerous differences based on gender.

A 1921 study, of the reports of college students regarding those traits in individuals which make for attractiveness and repulsiveness argued that static traits, such as beauty or ugliness of features, hold a position subordinate to groups of physical elements like expressive behavior, affectionate disposition, grace of manner, aristocratic bearing, social accomplishments, and personal habits.[25]

Grammer and colleagues have identified eight “pillars” of beauty: youthfulness, symmetry, averageness, sex-hormone markers, body odor, motion, skin complexion and hair texture.[26]

Most studies of the brain activations associated with the perception of attractiveness show photographs of faces to their participants and let them or a comparable group of people rate the attractiveness of these faces. Such studies consistently find that activity in certain parts of the orbitofrontal cortex increases with increasing attractiveness of faces.[27][28][29][30][31] This neural response has been interpreted as a reaction on the rewarding nature of attractiveness, as similar increases in activation in the medial orbitofrontal cortex can be seen in response to smiling faces[32] and to statements of morally good actions.[29][31] While most of these studies have not assessed participants of both genders or homosexual individuals, evidence from one study including male and female hetero- and homosexual individuals indicate that some of the aforementioned increases in brain activity are restricted to images of faces of the gender participants feel sexually attracted to.[33]

With regard to brain activation related to the perception of attractive bodies, one study with heterosexual participants suggests that activity in the nucleus accumbens and the anterior cingulate cortex increases with increasing attractiveness. The same study finds that for faces and bodies alike, the medial part of the orbitofrontal cortex responds with greater activity to both very attractive and very unattractive pictures.[34]

Women, on average, tend to be more attracted to men who have a relatively narrow waist, a V-shaped torso, and broad shoulders. Women also tend to be more attracted to men who are taller than they are, and display a high degree of facial symmetry, as well as relatively masculine facial dimorphism.[15][16] With regard to male-male-attractiveness, one source reports that the most important factor that attracts gay men to other males is the man’s physical attractiveness.[35]

Studies have shown that ovulating heterosexual women prefer faces with masculine traits associated with increased exposure to testosterone during key developmental stages, such as a broad forehead, relatively longer lower face, prominent chin and brow, chiseled jaw and defined cheekbones.[36] The degree of differences between male and female anatomical traits is called sexual dimorphism. Female respondents in the follicular phase of their menstrual cycle were significantly more likely to choose a masculine face than those in menses and luteal phases,[37] (or in those taking hormonal contraception).[15][16][38][39] This distinction supports the sexy son hypothesis, which posits that it is evolutionarily advantageous for women to select potential fathers who are more genetically attractive,[40] rather than the best caregivers.[41] However, women’s likeliness to exert effort to view male faces does not seem to depend on their masculinity, but to a general increase with women’s testosterone levels.[42]

It is suggested that the masculinity of facial features is a reliable indication of good health, or, alternatively, that masculine-looking males are more likely to achieve high status.[43] However, the correlation between attractive facial features and health has been questioned.[44] Sociocultural factors, such as self-perceived attractiveness, status in a relationship and degree of gender-conformity, have been reported to play a role in female preferences for male faces.[45] Studies have found that women who perceive themselves as physically attractive are more likely to choose men with masculine facial dimorphism, than are women who perceive themselves as physically unattractive.[46] In men, facial masculinity significantly correlates with facial symmetryit has been suggested that both are signals of developmental stability and genetic health.[47] One study called into question the importance of facial masculinity in physical attractiveness in men arguing that when perceived health, which is factored into facial masculinity, is discounted it makes little difference in physical attractiveness.[48] In a cross-country study involving 4,794 women in their early twenties, a difference was found in women’s average “masculinity preference” between countries.[49]

A study found that the same genetic factors cause facial masculinity in both males and females such that a male with a more masculine face would likely have a sister with a more masculine face due to the siblings having shared genes. The study also found that, although female faces that were more feminine were judged to be more attractive, there was no association between male facial masculinity and male facial attractiveness for female judges. With these findings, the study reasoned that if a woman were to reproduce with a man with a more masculine face, then her daughters would also inherit a more masculine face, making the daughters less attractive. The study concluded that there must be other factors that advantage the genetics for masculine male faces to offset their reproductive disadvantage in terms of “health”, “fertility” and “facial attractiveness” when the same genetics are present in females. The study reasoned that the “selective advantage” for masculine male faces must “have (or had)” been due to some factor that is not directly tied to female perceptions of male facial attractiveness.[50]

In a study of 447 gay men in China, researchers said that tops preferred feminized male faces, bottoms preferred masculinized male faces and versatiles had no preference for either feminized or masculinized male faces.[51]

In pre-modern Chinese literature, the ideal man in caizi jiaren romances was said to have “rosy lips, sparkling white teeth” and a “jasper-like face” (Chinese: ).[52][53]

In Middle English literature, a beautiful man should have a long, broad and strong face.[54]

A study that used Chinese, Malay and Indian judges said that Chinese men with orthognathism where the mouth is flat and in-line with the rest of the face were judged to be the most attractive and Chinese men with a protruding mandible where the jaw projects outward were judged to be the least attractive.[55]

Symmetrical faces and bodies may be signs of good inheritance to women of child-bearing age seeking to create healthy offspring. Studies suggest women are less attracted to men with asymmetrical faces,[56] and symmetrical faces correlate with long term mental performance[57] and are an indication that a man has experienced “fewer genetic and environmental disturbances such as diseases, toxins, malnutrition or genetic mutations” while growing.[57] Since achieving symmetry is a difficult task during human growth, requiring billions of cell reproductions while maintaining a parallel structure, achieving symmetry is a visible signal of genetic health.

Studies have also suggested that women at peak fertility were more likely to fantasize about men with greater facial symmetry,[58] and other studies have found that male symmetry was the only factor that could significantly predict the likelihood of a woman experiencing orgasm during sex. Women with partners possessing greater symmetry reported significantly more copulatory female orgasms than were reported by women with partners possessing low symmetry, even with many potential confounding variables controlled.[59] This finding has been found to hold across different cultures. It has been argued that masculine facial dimorphism (in men) and symmetry in faces are signals advertising genetic quality in potential mates.[60] Low facial and body fluctuating asymmetry may indicate good health and intelligence, which are desirable features.[61] Studies have found that women who perceive themselves as being more physically attractive are more likely to favor men with a higher degree of facial symmetry, than are women who perceive themselves as being less physically attractive.[46] It has been found that symmetrical men (and women) have a tendency to begin to have sexual intercourse at an earlier age, to have more sexual partners, and to have more one-night stands. They are also more likely to be prone to infidelity.[62] A study of quarterbacks in the American National Football League found a positive correlation between facial symmetry and salaries.[20]

Double-blind studies found that women prefer the scent of men who are rated as facially attractive.[63] For example, both males and females were more attracted to the natural scent of individuals who had been rated by consensus as facially attractive.[64] Additionally, it has also been shown that women have a preference for the scent of men with more symmetrical faces, and that women’s preference for the scent of more symmetrical men is strongest during the most fertile period of their menstrual cycle.[65] Within the set of normally cycling women, individual women’s preference for the scent of men with high facial symmetry correlated with their probability of conception.[65]

Studies have explored the genetic basis behind such issues as facial symmetry and body scent and how they influence physical attraction. In one study in which women wore men’s T-shirts, researchers found that women were more attracted to the bodily scents in shirts of men who had a different type of gene section within the DNA called Major histocompatibility complex (MHC).[66] MHC is a large gene area within the DNA of vertebrates which encodes proteins dealing with the immune system[67] and which influences individual bodily odors.[68] One hypothesis is that humans are naturally attracted by the sense of smell and taste to others with dissimilar MHC sections, perhaps to avoid subsequent inbreeding while increasing the genetic diversity of offspring.[67] Further, there are studies showing that women’s natural attraction for men with dissimilar immune profiles can be distorted with use of birth control pills.[68] Other research findings involving the genetic foundations of attraction suggest that MHC heterozygosity positively correlates with male facial attractiveness. Women judge the faces of men who are heterozygous at all three MHC loci to be more attractive than the faces of men who are homozygous at one or more of these loci. Additionally, a second experiment with genotyped women raters, found these preferences were independent of the degree of MHC similarity between the men and the female rater. With MHC heterozygosity independently seen as a genetic advantage, the results suggest that facial attractiveness in men may be a measure of genetic quality.[69][70]

A 2010 OkCupid study on 200,000 of its male and female dating site users found that women are, except those during their early to mid-twenties, open to relationships with both somewhat older and somewhat younger men; they have a larger potential dating pool than men until age 26. At age 20, women, in a “dramatic change”, begin sending private messages to significantly older men. At age 29 they become “even more open to older men”. Male desirability to women peaks in the late 20s and does not fall below the average for all men until 36.[71] Other research indicates that women, irrespective of their own age, are attracted to men who are the same age or older.[72]

For the Romans especially, “beardlessness” and “smooth young bodies” were considered beautiful to both men and women.[73] For Greek and Roman men, the most desirable traits of boys were their “youth” and “hairlessness”. Pubescent boys were considered a socially appropriate object of male desire, while post-pubescent boys were considered to be “” or “past the prime”.[73] This was largely in the context of pederasty (adult male interest in adolescent boys). Today, men and women’s attitudes towards male beauty has changed. For example, body hair on men may even be preferred (see below).

A 1984 study said that gay men tend to prefer gay men of the same age as ideal partners, but there was a statistically significant effect (p

The physique of a slim waist, broad shoulders and muscular chest are often found to be attractive to females.[75] Further research has shown that, when choosing a mate, the traits females look for indicate higher social status, such as dominance, resources, and protection.[76] An indicator of health in males (a contributing factor to physical attractiveness) is the android fat distribution pattern which is categorized as more fat distributed on the upper body and abdomen, commonly referred to as the “V shape.”[76] When asked to rate other men, both heterosexual and homosexual men found low waist-to-chest ratios (WCR) to be more attractive on other men, with the gay men showing a preference for lower WCR (more V-shaped) than the straight men.[77]

Other researchers found waist-to-chest ratio the largest determinant of male attractiveness, with body mass index and waist-to-hip ratio not as significant.[78]

Women focus primarily on the ratio waist to chest or more specifically waist to shoulder. This is analogous to the waist to hip ratio (WHR) that men prefer. Key body image for a man in the eyes of a woman would include big shoulders, chest, and upper back, and a slim waist area.[79] Research has additionally shown that college males had a better satisfaction with their body than college females. The research also found that when a college female’s waist to hip ratio went up, their body image satisfaction decreased.[80] The results indicate that males had significantly greater body image satisfaction than did females.

Some research has shown that body weight may have a stronger effect than WHR when it comes to perceiving attractiveness of the opposite sex. It was found that waist to hip ratio played a smaller role in body preference than body weight in regards to both sexes.[81]

Psychologists Viren Swami and Martin J. Tovee compared female preference for male attractiveness cross culturally, between Britain and Malaysia. They found that females placed more importance on WCR (and therefore body shape) in urban areas of Britain and Malaysia, while females in rural areas placed more importance on BMI (therefore weight and body size). Both WCR and BMI are indicative of male status and ability to provide for offspring, as noted by evolutionary theory.[82]

Females have been found to desire males that are normal weight and have the average WHR for a male. Females view these males as attractive and healthy. Males who had the average WHR but were overweight or underweight are not perceived as attractive to females. This suggests that WHR is not a major factor in male attractiveness, but a combination of body weight and a typical male WHR seem to be the most attractive. Research has shown that men who have a higher waist to hip ratio and a higher salary are perceived as more attractive to women.[83]

A 1982 study, found that an abdomen that protrudes was the “least attractive” trait for men.[84]

In Middle English literature, a beautiful man should have a flat abdomen.[54]

Men’s bodies portrayed in magazines marketed to men are more muscular than the men’s bodies portrayed in magazines marketed to women. From this, some have concluded that men perceive a more muscular male body to be ideal, as distinct from a woman’s ideal male, which is less muscular than what men perceive to be ideal.[85] This is due to the within-gender prestige granted by increased muscularity and within-gender competition for increased muscularity.[85] Men perceive the attractiveness of their own musculature by how closely their bodies resemble the “muscle man.”[86] This “muscle man” ideal is characterized by large muscular arms, especially biceps, a large muscular chest that tapers to their waist and broad shoulders.[86]

In a study of stated profile preferences on, a greater percentage of gay men than lesbians selected their ideal partner’s body type as “Athletic and Toned” as opposed to the other two options of “Average” or “Overweight”.[87]

In pre-modern Chinese literature, such as in The Story of the Western Wing, a type of masculinity called “scholar masculinity” is depicted wherein the “ideal male lover” is “weak, vulnerable, feminine, and pedantic”.[52]

In Middle English literature, a beautiful man should have thick, broad shoulders, a square and muscular chest, a muscular back, strong sides that taper to a small waist, large hands and arms and legs with huge muscles.[54]

A 2006 study, of 25,594 heterosexual men found that men who perceived themselves as having a large penis were more satisfied with their own appearance.[88]

A 2014 study, criticized previous studies based on the fact that they relied on images and used terms such as “small”, “medium”, and “large” when asking for female preference. The new study used 3D models of penises from sizes of 4 inches (10cm) long and 2.5 inches (6.4cm) in circumference to 8.5 inches (22cm) long and 7 inches (18cm) in circumference and let the women “view and handle” them. It was found that women overestimated the actual size of the penises they have experimented with when asked in a follow-up survey. The study concluded that women on average preferred the 6.5-inch (17cm) penis in length both for long-term and for one-time partners. Penises with larger girth were preferred for one-time partners.[89]

Females’ sexual attraction towards males may be determined by the height of the man.[91] Height in men is associated with status or wealth in many cultures (in particular those where malnutrition is common),[92] which is beneficial to women romantically involved with them. One study conducted of women’s personal ads support the existence of this preference; the study found that in ads requesting height in a mate, 80% requested a height of 6 feet (1.83m) or taller.[92] The online dating Website eHarmony only matches women with taller men because of complaints from women matched with shorter men.[93]

Other studies have shown that heterosexual women often prefer men taller than they are rather than a man with above average height. While women usually desire men to be at least the same height as themselves or taller, several other factors also determine male attractiveness, and the male-taller norm is not universal.[94] For example, taller women are more likely to relax the “taller male” norm than shorter women.[95] Furthermore, professor Adam Eyre-Walker, from the University of Sussex, has stated that there is, as of yet, no evidence that these preferences are evolutionary preferences, as opposed to merely cultural preferences.[96] In a double-blind study by Graziano et al., it was found that, in person, using a sample of women of normal size, they were on average most attracted to men who were of medium height (5’9″ 5’11”, 1.75m 1.80m) and less attracted to both men of shorter height (5’5″ 5’7″, 1.65m 1.70m) and men of tallest height (6’2″ 6’4″, 1.88m 1.93m).[97]

Additionally, women seem more receptive to an erect posture than men, though both prefer it as an element within beauty.[92] According to one study (Yee N., 2002), gay men who identify as “only tops” tend to prefer shorter men, while gay men who identify as “only bottoms” tend to prefer taller men.[98]

In romances in Middle English literature, all of the “ideal” male heroes are tall, and the vast majority of the “valiant” male heroes are tall too.[54]

Studies based in the United States, New Zealand, and China have shown that women rate men with no trunk (chest and abdominal) hair as most attractive, and that attractiveness ratings decline as hairiness increases.[99][100] Another study, however, found that moderate amounts of trunk hair on men was most attractive, to the sample of British and Sri Lankan women.[101] Further, a degree of hirsuteness (hairiness) and a waist-to-shoulder ratio of 0.6 is often preferred when combined with a muscular physique.[101]

In a study using Finnish women, women with hairy fathers were more likely to prefer hairy men, suggesting that preference for hairy men is the result of either genetics or imprinting.[102] Among gay men, another study (Yee N., 2002) reported gay males who identify as “only tops” prefer less hairy men, while gay males who identify as “only bottoms” prefer hairier men.[98]

Testosterone has been shown to darken skin color in laboratory experiments.[103] In his foreword to Peter Frost’s 2005 Fair Women, Dark Men, University of Washington sociologist Pierre L. van den Berghe writes: “Although virtually all cultures express a marked preference for fair female skin, even those with little or no exposure to European imperialism, and even those whose members are heavily pigmented, many are indifferent to male pigmentation or even prefer men to be darker.”[104] Despite this, the aesthetics of skin tone varies from culture to culture. Manual laborers who spent extended periods of time outside developed a darker skin tone due to exposure to the sun. As a consequence, an association between dark skin and the lower classes developed. Light skin became an aesthetic ideal because it symbolized wealth. “Over time society attached various meanings to these colored differences. Including assumptions about a person’s race, socioeconomic class, intelligence, and physical attractiveness.”[105]

A scientific review published in 2011, identified from a vast body of empirical research that skin colour as well as skin tone tend to be preferred as they act as indicators of good health. More specifically, these indicators are thought to suggest to potential mates that the beholder has strong or good genes capable of fighting off disease.[106]

According to one study (Yee N., 2002), gay men who identify as “only tops” tend to prefer lighter-skinned men while gay men who identify as “only bottoms” tend to prefer darker-skinned men.[98]

More recent research has suggested that redder and yellower skin tones,[107] reflecting higher levels of oxygenated blood,[108] carotenoid and to a lesser extent melanin pigment, and net dietary intakes of fruit and vegetables,[109] appears healthier, and therefore more attractive.[110]

Research indicates that heterosexual men tend to be attracted to young[111] and beautiful women[112] with bodily symmetry.[113] Rather than decreasing it, modernity has only increased the emphasis men place on women’s looks.[114]Evolutionary psychologists attribute such attraction to an evaluation of the fertility potential in a prospective mate.[111]

Research has attempted to determine which facial features communicate attractiveness. Facial symmetry has been shown to be considered attractive in women,[117][118] and men have been found to prefer full lips,[119] high forehead, broad face, small chin, small nose, short and narrow jaw, high cheekbones,[56][120] clear and smooth skin, and wide-set eyes.[111] The shape of the face in terms of “how everything hangs together” is an important determinant of beauty.[121] A University of Toronto study found correlations between facial measurements and attractiveness; researchers varied the distance between eyes, and between eyes and mouth, in different drawings of the same female face, and had the drawings evaluated; they found there were ideal proportions perceived as attractive (see photo).[115] These proportions (46% and 36%) were close to the average of all female profiles.[115] Women with thick, dark limbal rings in their eyes have also been found to be more attractive. The explanation given is that because the ring tends to fade with age and medical problems, a prominent limbal ring gives an honest indicator of youth.[122]

In a cross-cultural study, more neotenized (i.e., youthful looking) female faces were found to be most attractive to men while less neotenized female faces were found to be less attractive to men, regardless of the females’ actual age.[123] One of these desired traits was a small jaw.[124] In a study of Italian women who have won beauty competitions, it was found that their faces had more “babyish” (pedomorphic) traits than those of the “normal” women used as a reference.[125]

In a cross-cultural study, Marcinkowska et al. said that 18- to 45-year-old heterosexual men in all 28 countries surveyed preferred photographs of 18- to 24-year-old Caucasian women whose faces were feminized using Psychomorph software over faces of 18- to 24-year-old Caucasian women that were masculinized using that software, but there were differences in preferences for femininity across countries. The higher the National Health Index of a country, the more were the feminized faces preferred over the masculinized faces. Among the countries surveyed, Japan had the highest femininity preference and Nepal had the lowest femininity preference.[128]

Michael R. Cunningham of the Department of Psychology at the University of Louisville found, using a panel of East Asian, Hispanic and White judges, that the Asian, Hispanic and White female faces found most attractive were those that had “neonate large eyes, greater distance between eyes, and small noses”[129] and his study led him to conclude that “large eyes” were the most “effective” of the “neonate cues”.[129] Cunningham also said that “shiny” hair may be indicative of “neonate vitality”.[129] Using a panel of blacks and whites as judges, Cunningham found more neotenous faces were perceived as having both higher “femininity” and “sociability”.[129] In contrast, Cunningham found that faces that were “low in neoteny” were judged as “intimidating”.[129] Cunningham noted a “difference” in the preferences of Asian and white judges with Asian judges preferring women with “less mature faces” and smaller mouths than the White judges.[129] Cunningham hypothesized that this difference in preference may stem from “ethnocentrism” since “Asian faces possess those qualities”, so Cunningham re-analyzed the data with “11 Asian targets excluded” and concluded that “ethnocentrism was not a primary determinant of Asian preferences.”[129] Rather than finding evidence for purely “neonate” faces being most appealing, Cunningham found faces with “sexually-mature” features at the “periphery” of the face combined with “neonate” features in the “center of the face” most appealing in men and women.[129] Upon analyzing the results of his study, Cunningham concluded that preference for “neonate features may display the least cross-cultural variability” in terms of “attractiveness ratings”[129] and, in another study, Cunningham concluded that there exists a large agreement on the characteristics of an attractive face.[130][131]

In computer face averaging tests, women with averaged faces have been shown to be considered more attractive.[22][132] This is possibly due to average features being more familiar and, therefore, more comfortable.[117]

Commenting on the prevalence of whiteness in supposed beauty ideals in his book White Lies: Race and the Myth of Whiteness, Maurice Berger states that the schematic rendering in the idealized face of a study conducted with American subjects had “straight hair,” “light skin,” “almond-shaped eyes,” “thin, arched eyebrows,” “a long, thin nose, closely set and tiny nostrils” and “a large mouth and thin lips”,[133] though the author of the study stated that there was consistency between his results and those conducted on other races. Scholar Liu Jieyu says in the article White Collar Beauties, “The criterion of beauty is both arbitrary and gendered. The implicit consensus is that women who have fair skin and a slim figure with symmetrical facial features are pretty.” He says that all of these requirements are socially constructed and force people to change themselves to fit these criteria.[134]

One psychologist speculated there were two opposing principles of female beauty: prettiness and rarity. So on average, symmetrical features are one ideal, while unusual, stand-out features are another.[135] A study performed by the University of Toronto found that the most attractive facial dimensions were those found in the average female face. However, that particular University of Toronto study looked only at white women.[136]

A study that used Chinese, Malay and Indian judges said that Chinese women with orthognathism where the mouth is flat and in-line with the rest of the face were judged to be the most attractive and Chinese women with a protruding mandible where the jaw projects outward were judged to be the least attractive.[55]

A 2011 study, by Wilkins, Chan and Kaiser found correlations between perceived femininity and attractiveness, that is, women’s faces which were seen as more feminine were judged by both men and women to be more attractive.[137]

A component of the female beauty ideal in Persian literature is for women to have faces like a full moon.[138][139][140]

In Arabian society in the Middle Ages, a component of the female beauty ideal was for women to have round faces which were like a “full moon”.[141]

In Japan, during the Edo period, a component of the female beauty ideal was for women to have long and narrow faces which were shaped like ovals.[142]

In Jewish Rabbinic literature, the Rabbis considered full lips to be the ideal type of lips for women.[143]

Historically, in Chinese and Japanese literature, the feminine ideal was said to include small lips.[144] Women would paint their lips thinner and narrower to align with this ideal.[145][146]

Classical Persian literature, paintings, and miniatures portrayed traits such as long black curly hair, a small mouth, long arched eyebrows, large almond shaped eyes, a small nose, and beauty spots as being beautiful for women.[147]

Evidence from various cultures suggests that heterosexual men tend to find the sight of women’s genitalia to be sexually arousing.[148]

Cross-cultural data shows that the reproductive success of women is tied to their youth and physical attractiveness[149] such as the pre-industrial Sami where the most reproductively successful women were 15 years younger than their man.[150] One study covering 37 cultures showed that, on average, a woman was 2.5 years younger than her male partner, with the age difference in Nigeria and Zambia being at the far extreme of 6.5 to 7.5 years. As men age, they tend to seek a mate who is ever younger.[111]

25% of eHarmony’s male customers over the age of 50 request to only be matched with women younger than 40.[93] A 2010 OkCupid study, of 200,000 users found that female desirability to its male users peaks at age 21, and falls below the average for all women at 31. After age 26, men have a larger potential dating pool than women on the site; and by age 48, their pool is almost twice as large. The median 31-year-old male user searches for women aged 22 to 35, while the median 42-year-old male searches for women 27 to 45. The age skew is even greater with messages to other users; the median 30-year-old male messages teenage girls as often as women his own age, while mostly ignoring women a few years older than him. Excluding the 10% most and 10% least beautiful of women, however, women’s attractiveness does not change between 18 and 40, but if extremes are not excluded “There’s no doubt that younger [women] are more physically attractiveindeed in many ways beauty and youth are inextricable. That’s why most of the models you see in magazines are teenagers”.[71]

Pheromones (detected by female hormone markers) reflects female fertility and the reproductive value mean.[151] As females age, the estrogen-to-androgen production ratio changes and results in female faces to appear more and more masculine (thus appearing less “attractive”).[151] In a small (n=148) study performed in the United States, using male college students at one university, the mean age expressed as ideal for a wife was found to be 16.87 years old, while 17.76 was the mean ideal age for a brief sexual encounter. However, the study sets up a framework where “taboos against sex with young girls” are purposely diminished, and biased their sample by removing any participant over the age of 30, with a mean participant age of 19.83.[152] In a study of penile tumescence, men were found most aroused by pictures of young adult females.[153]

Signals of fertility in women are often also seen as signals of youth. The evolutionary perspective proposes the idea that when it comes to sexual reproduction, the minimal parental investment required by men gives them the ability and want to simply reproduce ‘as much as possible.'[154] It therefore makes sense that men are attracted to the features in women which signal youthfulness, and thus fertility.[154] Their chances of reproductive success are much higher than they would be should they pick someone olderand therefore less fertile.

This may explain why combating age declines in attractiveness occurs from a younger age in women than in men. For example, the removal of one’s body hair is considered a very feminine thing to do.[155] This can be explained by the fact that aging results in raised levels of testosterone and thus, body hair growth. Shaving reverts one’s appearance to a more youthful stage[155] and although this may not be an honest signal, men will interpret this as a reflection of increased fertile value. Research supports this, showing hairlessness to considered sexually attractive by men.[156]

Research has shown that most heterosexual men enjoy the sight of female breasts,[157] with a preference for large, firm breasts.[158] However, a contradictory study of British undergraduates found younger men preferred small breasts on women.[159] Smaller breasts were widely associated with youthfulness.[160] Cross-culturally, another study found “high variability” regarding the ideal breast size.[159] Some researchers in the United Kingdom have speculated that a preference for larger breasts may have developed in Western societies because women with larger breasts tend to have higher levels of the hormones estradiol and progesterone, which both promote fertility.[161]

A study showed that men prefer symmetrical breasts.[113][162] Breast symmetry may be particularly sensitive to developmental disturbances and the symmetry differences for breasts are large compared to other body parts. Women who have more symmetrical breasts tend to have more children.[163]

Historical literature often includes specific features of individuals or a gender that are considered desirable. These have often become a matter of convention, and should be interpreted with caution. In Arabian society in the Middle Ages, a component of the female beauty ideal was for women to have small breasts.[141] In Persian literature, beautiful women are said to have breasts like pomegranates or lemons.[138] In the Chinese text “Jeweled Chamber Secrets” (Chinese: ) from the Six Dynasties period, the ideal woman was described as having firm breasts.[142] In Sanskrit literature, beautiful women are often said to have breasts so large that they cause the women to bend a little bit from their weight.[164] In Middle English literature, beautiful women should have small breasts that are round like an apple or a pear.[54]

Biological anthropologist Helen E. Fisher of the Center for Human Evolution Studies in the Department of Anthropology of Rutgers University said that, “perhaps, the fleshy, rounded buttocks… attracted males during rear-entry intercourse.”[166] Bobbi S. Low et al. of the School of Natural Resources and Environment at the University of Michigan, said the female “buttocks evolved in the context of females competing for the attention and parental commitment of powerful resource-controlling males” as an “honest display of fat reserves” that could not be confused with another type of tissue,[167] although T. M. Caro, professor in the Center for Population Biology and the Department of Wildlife, Fish, and Conservation Biology, at University of California, Davis, rejected that as being a necessary conclusion, stating that female fatty deposits on the hips improve “individual fitness of the female”, regardless of sexual selection.[167]

In a 1995 study, black men were more likely than white men to use the words “big” or “large” to describe their conception of an attractive woman’s posterior.[168]

Body Mass Index (BMI) is an important determinant to the perception of beauty.[169] Even though the Western ideal is for a thin woman, some cultures prefer plumper women,[129][170] which has been argued to support that attraction for a particular BMI merely is a cultural artifact.[170] The attraction for a proportionate body also influences an appeal for erect posture.[171] One cross-cultural survey comparing body-mass preferences among 300 of the most thoroughly studied cultures in the world showed that 81% of cultures preferred a female body size that in English would be described as “plump”.[172]

Availability of food influences which female body size is attractive which may have evolutionary reasons. Societies with food scarcities prefer larger female body size than societies that have plenty of food. In Western society males who are hungry prefer a larger female body size than they do when not hungry.[173]

In the United States, women overestimate men’s preferences for thinness in a mate. In one study, American women were asked to choose what their ideal build was and what they thought the build most attractive to men was. Women chose slimmer than average figures for both choices. When American men were independently asked to choose the female build most attractive to them, the men chose figures of average build. This indicates that women may be misled as to how thin men prefer women to be.[170] Some speculate that thinness as a beauty standard is one way in which women judge each other[135] and that thinness is viewed as prestigious for within-gender evaluations of other women.[citation needed] A reporter surmised that thinness is prized among women as a “sign of independence, strength and achievement.”[135] Some implicated the fashion industry for the promulgation of the notion of thinness as attractive.[174]

East Asians have historically preferred women whose bodies had small features. For example, during the Spring and Autumn period of Chinese history, women in Chinese harems wanted to have a thin body in order to be attractive for the Chinese emperor. Later, during the Tang Dynasty, a less thin body type was seen as most attractive for Chinese women.[175] In Arabian society in the Middle Ages, a component of the female beauty ideal was for women to be slender like a “cane” or a “twig”.[141] In the Chinese text “Jeweled Chamber Secrets” (Chinese: ) from the Six Dynasties period, the ideal woman was described as not being “large-boned”.[142]

In the Victorian era, women who adhered to Victorian ideals were expected to limit their food consumption to attain the ideal slim figure.[176] In Middle English literature, “slender” women are considered beautiful.[54]

A WHR of 0.7 for women has been shown to correlate strongly with general health and fertility. Women within the 0.7 range have optimal levels of estrogen and are less susceptible to major diseases such as diabetes, heart disease, and ovarian cancers.[178] Women with high WHR (0.80 or higher) have significantly lower pregnancy rates than women with lower WHRs (0.700.79), independent of their BMIs.[179][180] Female waist-to-hip ratio (WHR) has been proposed by evolutionary psychologists to be an important component of human male mate choice, because this trait is thought to provide a reliable cue to a woman’s reproductive value.[181]

Both men and women judge women with smaller waist-to-hip ratios more attractive.[182] Ethnic groups vary with regard to their ideal waist-to-hip ratio for women,[183] ranging from 0.6 in China,[184] to 0.8 or 0.9 in parts of South America and Africa,[185][186][187] and divergent preferences based on ethnicity, rather than nationality, have also been noted.[188][189] A study found the Machiguenga people, an isolated indigenous South American ethnic group, prefer women with high WHR (0.9).[190] The preference for heavier women, has been interpreted to belong to societies where there is no risk of obesity.[191]

In Chinese, the phrase “willow waist” (Chinese: ) is used to denote a beautiful woman by describing her waist as being slender like a willow branch.[142]

In the Victorian era, a small waist was considered the main trait of a beautiful woman.[176]

Most men tend to be taller than their female partner.[192] It has been found that, in Western societies, most men prefer shorter women. Having said this, height is a more important factor for a woman when choosing a man than it is for a man choosing a woman.[193] Men tend to view taller women as less attractive,[194] and people view heterosexual couples where the woman is taller to be less ideal.[194] Women who are 0.7 to 1.7 standard deviations below the mean female height have been reported to be the most reproductively successful,[195] since fewer tall women get married compared to shorter women.[194] However, in other ethnic groups, such as the Hadza, study has found that height is irrelevant in choosing a mate.[94]

In Middle English literature, ‘tallness’ is a characteristic of ideally beautiful women.[54]

A study using Polish participants by Sorokowski found 5% longer legs than average person leg to body ratio for both on man and woman was considered most attractive.[196] The study concluded this preference might stem from the influence of leggy runway models.[197] Another study using British and American participants, found “mid-ranging” leg-to-body ratios to be most ideal.[198]

A study by Swami et al. of British male and female undergraduates showed a preference for men with legs as long as the rest of their body and women with 40% longer legs than the rest of their body.[90] The researcher concluded that this preference might be influenced by American culture where long legged women are portrayed as more attractive.[90]

Marco Bertamini criticized the Swami et al. study for using a picture of the same person with digitally altered leg lengths which he felt would make the modified image appear unrealistic.[199] Bertamini also criticized the Swami study for only changing the leg length while keeping the arm length constant.[199] After accounting for these concerns in his own study, Bertamini’s study which used stick figures also found a preference for women with proportionately longer legs than men.[199] When Bertamini investigated the issue of possible sexual dimorphism of leg length, he found two sources that indicated that men usually have slightly proportionately longer legs than women or that differences in leg length proportion may not exist between men and women.[199] Following this review of existing literature on the subject, he conducted his own calculations using data from 1774 men and 2208 women. Using this data, he similarly found that men usually have slightly proportionately longer legs than women or that differences in leg length proportion may not exist between men and women. These findings made him rule out the possibility that a preference for women with proportionately longer legs than men is due proportionately longer legs being a secondary sex characteristic of women.[199]

According to some studies, most men prefer women with small feet,[200][201] such as in ancient China where foot binding was practiced.[202]

In Jewish Rabbinic literature, the Rabbis considered small feet to be the ideal type of feet for women.[143]

Men have been found to prefer long-haired women.[111][203][204] An evolutionary psychology explanation for this is that malnutrition and deficiencies in minerals and vitamins causes loss of hair or hair changes. Hair therefore indicates health and nutrition during the last 23 years. Lustrous hair is also often a cross-cultural preference.[205] One study reported non-Asian men to prefer blondes and Asian men to prefer black-haired women.[204]

A component of the female beauty ideal in Persian literature is for women to have black hair,[138] which was also preferred in Arabian society in the Middle Ages.[141] In Middle English literature, curly hair is a necessary component of a beautiful woman.[54]

The way an individual moves can indicate health and even age and influence attractiveness.[205] A study reflecting the views of 700 individuals and that involved animated representations of people walking, found that the physical attractiveness of women increased by about 50 percent when they walked with a hip sway. Similarly, the perceived attractiveness of males doubled when they moved with a swagger in their shoulders.[206]

A preference for lighter-skinned women has remained prevalent over time, even in cultures without European contact, though exceptions have been found.[208] Anthropologist Peter Frost stated that since higher-ranking men were allowed to marry the perceived more attractive women, who tended to have fair skin, the upper classes of a society generally tended to develop a lighter complexion than the lower classes by sexual selection (see also Fisherian runaway).[104][208][209] In contrast, one study on men of the Bikosso tribe in Cameroon found no preference for attractiveness of females based on lighter skin color, bringing into question the universality of earlier studies that had exclusively focused on skin color preferences among non-African populations.[209]

Today, skin bleaching is not uncommon in parts of the world such as Africa,[210] and a preference for lighter-skinned women generally holds true for African Americans,[211] Latin Americans,[212] and Asians.[213] One exception to this has been in contemporary Western culture, where tanned skin used to be associated with the sun-exposed manual labor of the lower-class, but has generally been considered more attractive and healthier since the mid-20th century.[214][215][216][217][218]

More recent work has extended skin color research beyond preferences for lightness, arguing that redder (higher a* in the CIELab colour space) and yellower (higher b*) skin has healthier appearance.[107] These preferences have been attributed to higher levels of red oxygenated blood in the skin, which is associated with aerobic fitness and lack of cardiac and respiratory illnesses,[108] and to higher levels of yellow-red antioxidant carotenoids in the skin, indicative of more fruit and vegetables in the diet and, possibly more efficient immune and reproductive systems.[109]

Research has additionally shown that skin radiance or glowing skin indicates health, thus skin radiance influences perception of beauty and physical attractiveness.[219][220]

In Persian literature, beautiful women are said to have noses like hazelnuts.[138]

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Physical attractiveness – Wikipedia

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Prolactin – Wikipedia

PRL Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes

1RW5, 2Q98, 3D48, 3EW3, 3MZG, 3N06, 3N0P, 3NCB, 3NCC, 3NCE, 3NCF, 3NPZ

Prolactin (PRL), also known as luteotropic hormone or luteotropin, is a protein that in humans is best known for its role in enabling mammals, usually females, to produce milk. It is influential in over 300 separate processes in various vertebrates.[4] Prolactin is secreted from the pituitary gland in response to eating, mating, estrogen treatment, ovulation and nursing. Prolactin is secreted in pulses in between these events. Prolactin plays an essential role in metabolism, regulation of the immune system and pancreatic development.

Discovered in non-human animals around 1930 by Oscar Riddle[5] and confirmed in humans in 1970 by Henry Friesen[6] prolactin is a peptide hormone, encoded by the PRL gene.[7]

It is associated with human milk production. In fish it is thought to be related to control of water and salt balance. Prolactin also acts in a cytokine-like manner and as an important regulator of the immune system. It has important cell cycle-related functions as a growth-, differentiating- and anti-apoptotic factor. As a growth factor, binding to cytokine-like receptors, it influences hematopoiesis, angiogenesis and is involved in the regulation of blood clotting through several pathways. The hormone acts in endocrine, autocrine and paracrine manner through the prolactin receptor and a large number of cytokine receptors.[4]

Pituitary prolactin secretion is regulated by endocrine neurons in the hypothalamus. The most important ones are the neurosecretory tuberoinfundibulum (TIDA) neurons of the arcuate nucleus that secrete dopamine (aka Prolactin Inhibitory Hormone) to act on the D2 receptors of lactotrophs, causing inhibition of prolactin secretion. Thyrotropin-releasing factor (thyrotropin-releasing hormone) has a stimulatory effect on prolactin release, however prolactin is the only adenohypophyseal hormone whose principal control is inhibitory.

Several variants and forms are known per species. Many fish have variants prolactin A and prolactin B. Most vertebrates including humans also have the closely related somatolactin. In humans, three smaller (4, 16 and 22kDa) and several larger (so called big and big-big) variants exist.[not verified in body]

Prolactin has a wide variety of effects. It stimulates the mammary glands to produce milk (lactation): increased serum concentrations of prolactin during pregnancy cause enlargement of the mammary glands and prepare for milk production, which normally starts when the levels of progesterone fall by the end of pregnancy and a suckling stimulus is present. Sometimes, newborns (males as well as females) secrete a milky substance from their nipples known as witch’s milk. This is in part caused by maternal prolactin and other hormones. Prolactin plays an important role in maternal behavior.[8]

Prolactin provides the body with sexual gratification after sexual acts: The hormone counteracts the effect of dopamine, which is linked to sexual arousal. This is thought to cause the sexual refractory period. The amount of prolactin can be an indicator for the amount of sexual satisfaction and relaxation. Unusually high amounts are suspected to be responsible for impotence and loss of libido (see hyperprolactinemia symptoms).

Elevated levels of prolactin decrease the levels of sex hormones estrogen in women and testosterone in men.[9] The effects of mildly elevated levels of prolactin are much more variable, in women, substantially increasing or decreasing estrogen levels.

Prolactin is sometimes classified as a gonadotropin[10] although in humans it has only a weak luteotropic effect while the effect of suppressing classical gonadotropic hormones is more important.[11] Prolactin within the normal reference ranges can act as a weak gonadotropin, but at the same time suppresses GnRH secretion. The exact mechanism by which it inhibits GnRH is poorly understood. Although expression of prolactin receptors (PRL-R) have been demonstrated in rat hypothalamus, the same has not been observed in GnRH neurons.[12] Physiologic levels of prolactin in males enhance luteinizing hormone-receptors in Leydig cells, resulting in testosterone secretion, which leads to spermatogenesis.[13]

Prolactin also stimulates proliferation of oligodendrocyte precursor cells. These cells differentiate into oligodendrocytes, the cells responsible for the formation of myelin coatings on axons in the central nervous system.[14]

Other actions include contributing to pulmonary surfactant synthesis of the fetal lungs at the end of the pregnancy and immune tolerance of the fetus by the maternal organism during pregnancy. Prolactin delays hair regrowth in mice.[15] Prolactin promotes neurogenesis in maternal and fetal brains.[16][17]

In humans, prolactin is produced at least in the anterior pituitary, decidua, myometrium, breast, lymphocytes, leukocytes and prostate.[18][19]

Pituitary PRL is controlled by the Pit-1 transcription factor that binds to the prolactin gene at several sites. Ultimately dopamine, extrapituitary PRL is controlled by a superdistal promoter and apparently unaffected by dopamine.[19] The thyrotropin-releasing hormone and the vasoactive intestinal peptide stimulate the secretion of prolactin in experimental settings, however their physiological influence is unclear. The main stimulus for prolactin secretion is suckling, the effect of which is neuronally mediated.[20] A key regulator of prolactin production is estrogens that enhance growth of prolactin-producing cells and stimulate prolactin production directly, as well as suppressing dopamine.

In decidual cells and in lymphocytes the distal promoter and thus prolactin expression is stimulated by cAMP. Responsivness to cAMP is mediated by an imperfect cAMPresponsive element and two CAAT/enhancer binding proteins (C/EBP).[19]Progesterone upregulates prolactin synthesis in the endometrium and decreases it in myometrium and breast glandular tissue.[21] Breast and other tissues may express the Pit-1 promoter in addition to the distal promoter.

Extrapituitary production of prolactin is thought to be special to humans and primates and may serve mostly tissue specific paracrine and autocrine purposes. It has been hypothesized that in vertebrates such as mice a similar tissue specific effect is achieved by a large family of prolactin-like proteins controlled by at least 26 paralogous PRL genes not present in primates.[19]

Vasoactive intestinal peptide and peptide histidine isoleucine help to regulate prolactin secretion in humans, but the functions of these hormones in birds can be quite different.[22]

Prolactin follows diurnal and ovulatory cycles. Prolactin levels peak during REM sleep and in the early morning. Many mammals experience a seasonal cycle.

During pregnancy, high circulating concentrations of estrogen and progesterone increase prolactin levels by 10- to 20-fold. Estrogen and progesterone inhibit the stimulatory effects of prolactin on milk production. The abrupt drop of estrogen and progesterone levels following delivery allow prolactinwhich temporarily remains highto induce lactation.[verification needed]

Sucking on the nipple offsets the fall in prolactin as the internal stimulus for them is removed. The sucking activates mechanoreceptors in and around the nipple. These signals are carried by nerve fibers through the spinal cord to the hypothalamus, where changes in the electrical activity of neurons that regulate the pituitary gland increase prolactin secretion. The suckling stimulus also triggers the release of oxytocin from the posterior pituitary gland, which triggers milk let-down: Prolactin controls milk production (lactogenesis) but not the milk-ejection reflex; the rise in prolactin fills the breast with milk in preparation for the next feed.

In usual circumstances, in the absence of galactorrhea, lactation ceases within one or two weeks following the end of breastfeeding.

Compared to un-mated males, fathers and expectant fathers have increased prolactin concentrations.[23]

Levels can rise after exercise, high-protein meals,[24]sexual intercourse, breast examination,[24] minor surgical procedures,[25] following epileptic seizures[26] or due to physical or emotional stress.[24][27] In a study on female volunteers under hypnosis, prolactin surges resulted from the evocation, with rage, of humiliating experiences, but not from the fantasy of nursing.[27]

Prolactin levels have also been found to rise with use of the drug MDMA (Ecstasy), leading to speculation that prolactin may have a role in the post-orgasmic state as well as decreased sexual desire.[28]

Hypersecretion is more common than hyposecretion. Hyperprolactinemia is the most frequent abnormality of the anterior pituitary tumors, termed prolactinomas. Prolactinomas may disrupt the hypothalamic-pituitary-gonadal axis as prolactin tends to suppress the secretion of GnRH from the hypothalamus and in turn decreases the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary, therefore disrupting the ovulatory cycle.[29] Such hormonal changes may manifest as amenorrhea and infertility in females as well as impotence in males. Inappropriate lactation (galactorrhoea) is another important clinical sign of prolactinomas.

The structure of prolactin is similar to that of growth hormone and placental lactogen. The molecule is folded due to the activity of three disulfide bonds. Significant heterogeneity of the molecule has been described, thus bioassays and immunoassays can give different results due to differing glycosylation, phosphorylationsandulfation, as well as degradation. The non-glycosylated form of prolactin is the dominant form at is secreted by the pituitary gland.

The three different sizes of prolactin are:

The levels of larger ones are somewhat higher during the early postpartum period.[33]

Prolactin receptors are present in the mammillary glands, ovaries, pituitary glands, heart, lung, thymus, spleen, liver, pancreas, kidney, adrenal gland, uterus, skeletal muscle, skin and areas of the central nervous system.[34] When prolactin binds to the receptor, it causes it to dimerize with another prolactin receptor. This results in the activation of Janus kinase 2, a tyrosine kinase that initiates the JAK-STAT pathway. Activation also results in the activation of mitogen-activated protein kinases and Src kinase.[34]

Human prolactin receptors are insensitive to mouse prolactin.[35]

Prolactin levels may be checked as part of a sex hormone workup, as elevated prolactin secretion can suppress the secretion of FSH and GnRH, leading to hypogonadism and sometimes causing erectile dysfunction.

Prolactin levels may be of some use in distinguishing epileptic seizures from psychogenic non-epileptic seizures. The serum prolactin level usually rises following an epileptic seizure.[36]

The serum concentration of prolactin can be given in mass concentration (g/L or ng/mL), molar concentration (nmol/L or pmol/L) or in international units (typically mIU/L). The current IU is calibrated against the third International Standard for Prolactin, IS 84/500.[37][38] Reference ampoules of IS 84/500 contain 2.5g of lyophilized human prolactin[39] and have been assigned an activity of .053 International Units.[37][38] Measurements that are calibrated against the current international standard can be converted into mass units using this ratio of grams to IUs;[40] prolactin concentrations expressed in mIU/L can be converted to g/L by dividing by 21.2. Previous standards use other ratios.[41][42][43][44]

The first International Reference Preparation (or IRP) of human Prolactin for Immunoassay was established in 1978 (75/504 1st IRP for human Prolactin) at a time when purified human prolactin was in short supply.[40][41] Previous standards relied on prolactin from animal sources.[44] Purified human prolactin was scarce, heterogeneous, unstable and difficult to characterize. A preparation labelled 81/541 was distributed by the WHO Expert Committee on Biological Standardization without official status and given the assigned value of 50 mIU/ampoule based on an earlier collaborative study.[40][42] It was determined that this preparation behaved anomalously in certain immunoassays and was not suitable as an IS.[40]

Three different human pituitary extracts containing prolactin were subsequently obtained as candidates for an IS. These were distributed into ampoules coded 83/562, 83/573 and 84/500.[37][38][40][43] Collaborative studies involving 20 different laboratories found little difference between these three preparations. 83/562 appeared to be the most stable. This preparation was largely free of dimers and polymers of prolactin. On the basis of these investigations 83/562 was established as the Second IS for human Prolactin.[43] Once stocks of these ampoules were depleted, 84/500 was established as the Third IS for human Prolactin.[37][40]

General guidelines for diagnosing prolactin excess (hyperprolactinemia) define the upper threshold of normal prolactin at 25g/L for women and 20g/L for men.[34] Similarly, guidelines for diagnosing prolactin deficiency (hypoprolactinemia) are defined as prolactin levels below 3g/L in women[45][46] and 5g/L in men.[47][48][49] However, different assays and methods for measuring prolactin are employed by different laboratories and as such the serum reference range for prolactin is often determined by the laboratory performing the measurement.[34][50] Furthermore, prolactin levels also vary factors including age,[51] sex,[51]menstrual cycle stage[51] and pregnancy.[51] The circumstances surrounding a given prolactin measurement (assay, patient condition, etc.) must therefore be considered before the measurement can be accurately interpreted.[34]

The following chart illustrates the variations seen in normal prolactin measurements across different populations. Prolactin values were obtained from specific control groups of varying sizes using the IMMULITE assay.[51]

The following table illustrates variability in reference ranges of serum prolactin between some commonly used assay methods (as of 2008), using a control group of healthy health care professionals (53 males, age 2064 years, median 28 years; 97 females, age 1959 years, median 29 years) in Essex, England:[50]

An example usage of table above is, if using the Centaur assay to estimate prolactin values in g/L for females, the mean is 7.92g/L and the reference range is 3.3516.4g/L.

Hyperprolactinaemia, or excess serum prolactin, is associated with hypoestrogenism, anovulatory infertility, oligomenorrhoea, amenorrhoea, unexpected lactation and loss of libido in women and erectile dysfunction and loss of libido in men.[53]

Hypoprolactinemia, or serum prolactin deficiency, is associated with ovarian dysfunction in women,[45][46] and arteriogenic erectile dysfunction, premature ejaculation,[47]oligozoospermia, asthenospermia, hypofunction of seminal vesicles and hypoandrogenism[48] in men. In one study, normal sperm characteristics were restored when prolactin levels were raised to normal values in hypoprolactinemic men.[49]

Hypoprolactinemia can result from hypopituitarism, excessive dopaminergic action in the tuberoinfundibular pathway and ingestion of D2 receptor agonists such as bromocriptine.

While there is evidence that women who smoke tend to breast feed for shorter periods, there is a wide variation of breast-feeding rates in women who do smoke. This suggest that psychosocial factors rather than physiological mechanisms (e.g., nicotine suppressing prolactin levels) are responsible for the lower rates of breast feeding in women who do smoke.[54][55]

Prolactin is available commercially for use in animals, but not in humans.[56] It is used to stimulate lactation in animals.[56] The biological half-life of prolactin in humans is around 1520 minutes.[57] The D2 receptor is involved in the regulation of prolactin secretion, and agonists of the receptor such as bromocriptine and cabergoline decrease prolactin levels while antagonists of the receptor such as domperidone, metoclopramide, haloperidol, risperidone, and sulpiride increase prolactin levels.[58] D2 receptor antagonists like domperidone, metoclopramide, and sulpiride are used as galactogogues to increase prolatin secretion and induce lactation in humans.[59]

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Bone – Wikipedia

A bone is a rigid organ that constitutes part of the vertebral skeleton. Bones support and protect the various organs of the body, produce red and white blood cells, store minerals and also enable mobility as well as support for the body. Bone tissue is a type of dense connective tissue. Bones come in a variety of shapes and sizes and have a complex internal and external structure. They are lightweight yet strong and hard, and serve multiple functions. Mineralized osseous tissue, or bone tissue, is of two types, cortical and cancellous, and gives a bone rigidity and a coral-like three-dimensional internal structure. Other types of tissue found in bones include marrow, endosteum, periosteum, nerves, blood vessels and cartilage.

Bone is an active tissue composed of different types of bone cells. Osteoblasts and osteocytes are involved in the creation and mineralisation of bone; osteoclasts are involved in the reabsorption of bone tissue. The mineralised matrix of bone tissue has an organic component of mainly collagen called ossein and an inorganic component of bone mineral made up of various salts.

In the human body at birth, there are over 270 bones,[1] but many of these fuse together during development, leaving a total of 206 separate bones in the adult,[2] not counting numerous small sesamoid bones. The largest bone in the body is the thigh-bone (femur) and the smallest is the stapes in the middle ear.

Bone is not a uniformly solid material, but is mostly a matrix. The primary tissue of bone, bone tissue (osseous tissue), is relatively hard and lightweight. Its matrix is mostly made up of a composite material incorporating the inorganic mineral calcium phosphate in the chemical arrangement termed calcium hydroxylapatite (this is the bone mineral that gives bones their rigidity) and collagen, an elastic protein which improves fracture resistance.[3] Bone is formed by the hardening of this matrix around entrapped cells. When these cells become entrapped from osteoblasts they become osteocytes.[citation needed]

The hard outer layer of bones is composed of cortical bone also called compact bone. Cortical referring to the outer (cortex) layer. The hard outer layer gives bone its smooth, white, and solid appearance, and accounts for 80% of the total bone mass of an adult human skeleton.[citation needed] However, that proportion may be much lower, especially in marine mammals and marine turtles, or in various Mesozoic marine reptiles, such as ichthyosaurs,[4] among others.[5]

Cortical bone consists of multiple microscopic columns, each called an osteon. Each column is multiple layers of osteoblasts and osteocytes around a central canal called the Haversian canal. Volkmann’s canals at right angles connect the osteons together. The columns are metabolically active, and as bone is reabsorbed and created the nature and location of the cells within the osteon will change. Cortical bone is covered by a periosteum on its outer surface, and an endosteum on its inner surface. The endosteum is the boundary between the cortical bone and the cancellous bone.

Filling the interior of the bone is the cancellous bone also known as trabecular or spongy bone tissue. It is an open cell porous network. Thin formations of osteoblasts covered in endosteum create an irregular network of spaces. Within these spaces are bone marrow and hematopoietic stem cells that give rise to platelets, red blood cells and white blood cells. Trabecular marrow is composed of a network of rod- and plate-like elements that make the overall organ lighter and allow room for blood vessels and marrow. Trabecular bone accounts for the remaining 20% of total bone mass but has nearly ten times the surface area of compact bone.[8]

Bone marrow, also known as myeloid tissue, can be found in almost any bone that holds cancellous tissue. In newborns, all such bones are filled exclusively with red marrow, but as the child ages it is mostly replaced by yellow, or fatty marrow. In adults, red marrow is mostly found in the bone marrow of the femur, the ribs, the vertebrae and pelvic bones.[citation needed]

Bone is a metabolically active tissue composed of several types of cells. These cells include osteoblasts, which are involved in the creation and mineralization of bone tissue, osteocytes, and osteoclasts, which are involved in the reabsorption of bone tissue. Osteoblasts and osteocytes are derived from osteoprogenitor cells, but osteoclasts are derived from the same cells that differentiate to form macrophages and monocytes. Within the marrow of the bone there are also hematopoietic stem cells. These cells give rise to other cells, including white blood cells, red blood cells, and platelets.

Bones consist of living cells embedded in a mineralized organic matrix. This matrix consists of organic components, mainly collagen “organic” referring to materials produced as a result of the human body and inorganic components, primarily hydroxyapatite and other salts of calcium and phosphate. Above 30% of the acellular part of bone consists of the organic components, and 70% of salts. The strands of collagen give bone its tensile strength, and the interspersed crystals of hydroxyapatite give bone its compressional strength. These effects are synergistic.

The inorganic composition of bone (bone mineral) is primarily formed from salts of calcium and phosphate, the major salt being hydroxyapatite (Ca10(PO4)6(OH)2). The exact composition of the matrix may change over time and with nutrition, with the ratio of calcium to phosphate varying between 1.3 and 2.0 (per weight), and trace minerals such as magnesium, sodium, potassium and carbonate also being found.

The organic part of matrix is mainly composed of Type I collagen. Collagen composes 9095% of the organic matrix, with remainder of the matrix being a homogenous liquid called ground substance consisting of proteoglycans such as hyaluronic acid and chondroitin sulfate. Collagen consists of strands of repeating units, which give bone tensile strength, and are arranged in an overlapping fashion that prevents shear stress. The function of ground substance is not fully known. Two types of bone can be identified microscopically according to the arrangement of collagen:

Woven bone is produced when osteoblasts produce osteoid rapidly, which occurs initially in all fetal bones, but is later replaced by more resilient lamellar bone. In adults woven bone is created after fractures or in Paget’s disease. Woven bone is weaker, with a smaller number of randomly oriented collagen fibers, but forms quickly; it is for this appearance of the fibrous matrix that the bone is termed woven. It is soon replaced by lamellar bone, which is highly organized in concentric sheets with a much lower proportion of osteocytes to surrounding tissue. Lamellar bone, which makes its first appearance in humans in the fetus during the third trimester,[16] is stronger and filled with many collagen fibers parallel to other fibers in the same layer (these parallel columns are called osteons). In cross-section, the fibers run in opposite directions in alternating layers, much like in plywood, assisting in the bone’s ability to resist torsion forces. After a fracture, woven bone forms initially and is gradually replaced by lamellar bone during a process known as “bony substitution.” Compared to woven bone, lamellar bone formation takes place more slowly. The orderly deposition of collagen fibers restricts the formation of osteoid to about 1 to 2m per day. Lamellar bone also requires a relatively flat surface to lay the collagen fibers in parallel or concentric layers.[citation needed]

The extracellular matrix of bone is laid down by osteoblasts, which secrete both collagen and ground substance. These synthesise collagen within the cell, and then secrete collagen fibrils. The collagen fibres rapidly polymerise to form collagen strands. At this stage they are not yet mineralised, and are called “osteoid”. Around the strands calcium and phosphate precipitate on the surface of these strands, within a days to weeks becoming crystals of hydroxyapatite.

In order to mineralise the bone, the osteoblasts secrete vesicles containing alkaline phosphatase. This cleaves the phosphate groups and acts as the foci for calcium and phosphate deposition. The vesicles then rupture and act as a centre for crystals to grow on. More particularly, bone mineral is formed from globular and plate structures.[17][18]

There are five types of bones in the human body: long, short, flat, irregular, and sesamoid.[19]

In the study of anatomy, anatomists use a number of anatomical terms to describe the appearance, shape and function of bones. Other anatomical terms are also used to describe the location of bones. Like other anatomical terms, many of these derive from Latin and Greek. Some anatomists still use Latin to refer to bones. The term “osseous”, and the prefix “osteo-“, referring to things related to bone, are still used commonly today.

Some examples of terms used to describe bones include the term “foramen” to describe a hole through which something passes, and a “canal” or “meatus” to describe a tunnel-like structure. A protrusion from a bone can be called a number of terms, including a “condyle”, “crest”, “spine”, “eminence”, “tubercle” or “tuberosity”, depending on the protrusion’s shape and location. In general, long bones are said to have a “head”, “neck”, and “body”.

When two bones join together, they are said to “articulate”. If the two bones have a fibrous connection and are relatively immobile, then the joint is called a “suture”.

The formation of bone is called ossification. During the fetal stage of development this occurs by two processes, Intramembranous ossification and endochondral ossification.[citation needed] Intramembranous ossification involves the creation of bone from connective tissue, whereas in the process of endochondral ossification bone is created from cartilage.

Intramembranous ossification mainly occurs during formation of the flat bones of the skull but also the mandible, maxilla, and clavicles; the bone is formed from connective tissue such as mesenchyme tissue rather than from cartilage. The steps in intramembranous ossification are:[citation needed]

Endochondral ossification, on the other hand, occurs in long bones and most of the rest of the bones in the body; it involves an initial hyaline cartilage that continues to grow. The steps in endochondral ossification are:[citation needed]

Endochondral ossification begins with points in the cartilage called “primary ossification centers.” They mostly appear during fetal development, though a few short bones begin their primary ossification after birth. They are responsible for the formation of the diaphyses of long bones, short bones and certain parts of irregular bones. Secondary ossification occurs after birth, and forms the epiphyses of long bones and the extremities of irregular and flat bones. The diaphysis and both epiphyses of a long bone are separated by a growing zone of cartilage (the epiphyseal plate). When the child reaches skeletal maturity (18 to 25 years of age), all of the cartilage is replaced by bone, fusing the diaphysis and both epiphyses together (epiphyseal closure).[citation needed] In the upper limbs, only the diaphyses of the long bones and scapula are ossified. The epiphyses, carpal bones, coracoid process, medial border of the scapula, and acromion are still cartilaginous.[21]

The following steps are followed in the conversion of cartilage to bone:

Bones have a variety of functions:

Bones serve a variety of mechanical functions. Together the bones in the body form the skeleton. They provide a frame to keep the body supported, and an attachment point for skeletal muscles, tendons, ligaments and joints, which function together to generate and transfer forces so that individual body parts or the whole body can be manipulated in three-dimensional space (the interaction between bone and muscle is studied in biomechanics).

Bones protect internal organs, such as the skull protecting the brain or the ribs protecting the heart and lungs. Because of the way that bone is formed, bone has a high compressive strength of about 170 MPa (1800 kgf/cm),[3] poor tensile strength of 104121 MPa, and a very low shear stress strength (51.6 MPa).[23][24] This means that bone resists pushing(compressional) stress well, resist pulling(tensional) stress less well, but only poorly resists shear stress (such as due to torsional loads). While bone is essentially brittle, bone does have a significant degree of elasticity, contributed chiefly by collagen. The macroscopic yield strength of cancellous bone has been investigated using high resolution computer models.[25]

Mechanically, bones also have a special role in hearing. The ossicles are three small bones in the middle ear which are involved in sound transduction.

Cancellous bones contain bone marrow. Bone marrow produces blood cells in a process called hematopoiesis.[26] Blood cells that are created in bone marrow include red blood cells, platelets and white blood cells. Progenitor cells such as the hematopoietic stem cell divide in a process called mitosis to produce precursor cells. These include precursors which eventually give rise to white blood cells, and erythroblasts which give rise to red blood cells. Unlike red and white blood cells, created by mitosis, platelets are shed from very large cells called megakaryocytes. This process of progressive differentiation occurs within the bone marrow. After the cells are matured, they enter the circulation. Every day, over 2.5 billion red blood cells and platelets, and 50100 billion granulocytes are produced in this way.

As well as creating cells, bone marrow is also one of the major sites where defective or aged red blood cells are destroyed.

Bone is constantly being created and replaced in a process known as remodeling. This ongoing turnover of bone is a process of resorption followed by replacement of bone with little change in shape. This is accomplished through osteoblasts and osteoclasts. Cells are stimulated by a variety of signals, and together referred to as a remodeling unit. Approximately 10% of the skeletal mass of an adult is remodelled each year.[32] The purpose of remodeling is to regulate calcium homeostasis, repair microdamaged bones from everyday stress, and also to shape and sculpt the skeleton during growth.[citation needed]. Repeated stress, such as weight-bearing exercise or bone healing, results in the bone thickening at the points of maximum stress (Wolff’s law). It has been hypothesized that this is a result of bone’s piezoelectric properties, which cause bone to generate small electrical potentials under stress.[33]

The action of osteoblasts and osteoclasts are controlled by a number of chemical enzymes that either promote or inhibit the activity of the bone remodeling cells, controlling the rate at which bone is made, destroyed, or changed in shape. The cells also use paracrine signalling to control the activity of each other.[citation needed] For example, the rate at which osteoclasts resorb bone is inhibited by calcitonin and osteoprotegerin. Calcitonin is produced by parafollicular cells in the thyroid gland, and can bind to receptors on osteoclasts to directly inhibit osteoclast activity. Osteoprotegerin is secreted by osteoblasts and is able to bind RANK-L, inhibiting osteoclast stimulation.[34]

Osteoblasts can also be stimulated to increase bone mass through increased secretion of osteoid and by inhibiting the ability of osteoclasts to break down osseous tissue.[citation needed] Increased secretion of osteoid is stimulated by the secretion of growth hormone by the pituitary, thyroid hormone and the sex hormones (estrogens and androgens). These hormones also promote increased secretion of osteoprotegerin.[34] Osteoblasts can also be induced to secrete a number of cytokines that promote reabsorbtion of bone by stimulating osteoclast activity and differentiation from progenitor cells. Vitamin D, parathyroid hormone and stimulation from osteocytes induce osteoblasts to increase secretion of RANK-ligand and interleukin 6, which cytokines then stimulate increased reabsorption of bone by osteoclasts. These same compounds also increase secretion of macrophage colony-stimulating factor by osteoblasts, which promotes the differentiation of progenitor cells into osteoclasts, and decrease secretion of osteoprotegerin.[citation needed]

Bone volume is determined by the rates of bone formation and bone resorption. Recent research has suggested that certain growth factors may work to locally alter bone formation by increasing osteoblast activity. Numerous bone-derived growth factors have been isolated and classified via bone cultures. These factors include insulin-like growth factors I and II, transforming growth factor-beta, fibroblast growth factor, platelet-derived growth factor, and bone morphogenetic proteins.[35] Evidence suggests that bone cells produce growth factors for extracellular storage in the bone matrix. The release of these growth factors from the bone matrix could cause the proliferation of osteoblast precursors. Essentially, bone growth factors may act as potential determinants of local bone formation.[35] Research has suggested that trabecular bone volume in postemenopausal osteoporosis may be determined by the relationship between the total bone forming surface and the percent of surface resorption.[36]

A number of diseases can affect bone, including arthritis, fractures, infections, osteoporosis and tumours. Conditions relating to bone can be managed by a variety of doctors, including rheumatologists for joints, and orthopedic surgeons, who may conduct surgery to fix broken bones. Other doctors, such as rehabilitation specialists may be involved in recovery, radiologists in interpreting the findings on imaging, and pathologists in investigating the cause of the disease, and family doctors may play a role in preventing complications of bone disease such as osteoporosis.

When a doctor sees a patient, a history and exam will be taken. Bones are then often imaged, called radiography. This might include ultrasound X-ray, CT scan, MRI scan and other imaging such as a Bone scan, which may be used to investigate cancer. Other tests such as a blood test for autoimmune markers may be taken, or a synovial fluid aspirate may be taken.

In normal bone, fractures occur when there is significant force applied, or repetitive trauma over a long time. Fractures can also occur when a bone is weakened, such as with osteoporosis, or when there is a structural problem, such as when the bone remodels excessively (such as Paget’s disease) or is the site of the growth of cancer. Common fractures include wrist fractures and hip fractures, associated with osteoporosis, vertebral fractures associated with high-energy trauma and cancer, and fractures of long-bones. Not all fractures are painful. When serious, depending on the fractures type and location, complications may include flail chest, compartment syndromes or fat embolism. Compound fractures involve the bone’s penetration through the skin.

Fractures and their underlying causes can be investigated by X-rays, CT scans and MRIs. Fractures are described by their location and shape, and several classification systems exist, depending on the location of the fracture. A common long bone fracture in children is a SalterHarris fracture.[39] When fractures are managed, pain relief is often given, and the fractured area is often immobilised. This is to promote bone healing. In addition, surgical measures such as internal fixation may be used. Because of the immobilisation, people with fractures are often advised to undergo rehabilitation.

There are several types of tumour that can affect bone; examples of benign bone tumours include osteoma, osteoid osteoma, osteochondroma, osteoblastoma, enchondroma, giant cell tumor of bone, aneurysmal bone cyst, and fibrous dysplasia of bone.

Cancer can arise in bone tissue, and bones are also a common site for other cancers to spread (metastasise) to. Cancers that arise in bone are called “primary” cancers, although such cancers are rare. Metastases within bone are “secondary” cancers, with the most common being breast cancer, lung cancer, prostate cancer, thyroid cancer, and kidney cancer. Secondary cancers that affect bone can either destroy bone (called a “lytic” cancer) or create bone (a “sclerotic” cancer). Cancers of the bone marrow inside the bone can also affect bone tissue, examples including leukemia and multiple myeloma. Bone may also be affected by cancers in other parts of the body. Cancers in other parts of the body may release parathyroid hormone or parathyroid hormone-related peptide. This increases bone reabsorption, and can lead to bone fractures.

Bone tissue that is destroyed or altered as a result of cancers is distorted, weakened, and more prone to fracture. This may lead to compression of the spinal cord, destruction of the marrow resulting in bruising, bleeding and immunosuppression, and is one cause of bone pain. If the cancer is metastatic, then there might be other symptoms depending on the site of the original cancer. Some bone cancers can also be felt.

Cancers of the bone are managed according to their type, their stage, prognosis, and what symptoms they cause. Many primary cancers of bone are treated with radiotherapy. Cancers of bone marrow may be treated with chemotherapy, and other forms of targeted therapy such as immunotherapy may be used.Palliative care, which focuses on maximising a person’s quality of life, may play a role in management, particularly if the likelihood of survival within five years is poor.

Osteoporosis is a disease of bone where there is reduced bone mineral density, increasing the likelihood of fractures. Osteoporosis is defined by the World Health Organization in women as a bone mineral density 2.5 standard deviations below peak bone mass, relative to the age and sex-matched average, as measured by Dual energy X-ray absorptiometry, with the term “established osteoporosis” including the presence of a fragility fracture.[43] Osteoporosis is most common in women after menopause, when it is called “postmenopausal osteoporosis”, but may develop in men and premenopausal women in the presence of particular hormonal disorders and other chronic diseases or as a result of smoking and medications, specifically glucocorticoids. Osteoporosis usually has no symptoms until a fracture occurs. For this reason, DEXA scans are often done in people with one or more risk factors, who have developed osteoporosis and be at risk of fracture.

Osteoporosis treatment includes advice to stop smoking, decrease alcohol consumption, exercise regularly, and have a healthy diet. Calcium supplements may also be advised, as may Vitamin D. When medication is used, it may include bisphosphonates, Strontium ranelate, and osteoporosis may be one factor considered when commencing Hormone replacement therapy.[44]

The study of bones and teeth is referred to as osteology. It is frequently used in anthropology, archeology and forensic science for a variety of tasks. This can include determining the nutritional, health, age or injury status of the individual the bones were taken from. Preparing fleshed bones for these types of studies can involve the process of maceration.

Typically anthropologists and archeologists study bone tools made by Homo sapiens and Homo neanderthalensis. Bones can serve a number of uses such as projectile points or artistic pigments, and can also be made from external bones such as antlers.

Bird skeletons are very lightweight. Their bones are smaller and thinner, to aid flight. Among mammals, bats come closest to birds in terms of bone density, suggesting that small dense bones are a flight adaptation. Many bird bones have little marrow due to their being hollow.[45]

A bird’s beak is primarily made of bone as projections of the mandibles which are covered in keratin.

A deer’s antlers are composed of bone which is an unusual example of bone being outside the skin of the animal once the velvet is shed.[46]

The extinct predatory fish Dunkleosteus had sharp edges of hard exposed bone along its jaws.[citation needed]

Many animals possess an exoskeleton that is not made of bone, These include insects and crustaceans.

Bones from slaughtered animals have a number of uses. In prehistoric times, they have been used for making bone tools. They have further been used in bone carving, already important in prehistoric art, and also in modern time as crafting materials for buttons, beads, handles, bobbins, calculation aids, head nuts, dice, poker chips, pick-up sticks, ornaments, etc. A special genre is scrimshaw.

Bone glue can be made by prolonged boiling of ground or cracked bones, followed by filtering and evaporation to thicken the resulting fluid. Historically once important, bone glue and other animal glues today have only a few specialized uses, such as in antiques restoration. Essentially the same process, with further refinement, thickening and drying, is used to make gelatin.

Broth is made by simmering several ingredients for a long time, traditionally including bones.

Ground bones are used as an organic phosphorus-nitrogen fertilizer and as additive in animal feed. Bones, in particular after calcination to bone ash, are used as source of calcium phosphate for the production of bone china and previously also phosphorus chemicals.[citation needed]

Bone char, a porous, black, granular material primarily used for filtration and also as a black pigment, is produced by charring mammal bones.

Oracle bone script was a writing system used in Ancient china based on inscriptions in bones.

To point the bone at someone is considered bad luck in some cultures, such as Australian aborigines, such as by the Kurdaitcha.

Osteopathic medicine is a school of medical thought originally developed based on the idea of the link between the musculoskeletal system and overall health, but now very similar to mainstream medicine. As of 2012[update], over 77,000 physicians in the United States are trained in Osteopathic medicine colleges.[47]

The wishbones of fowl have been used for divination, and are still customarily used in a tradition to determine which one of two people pulling on either prong of the bone may make a wish.

Various cultures throughout history have adopted the custom of shaping an infant’s head by the practice of artificial cranial deformation. A widely practised custom in China was that of foot binding to limit the normal growth of the foot.

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Bone – Wikipedia

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Gene – Wikipedia

This article is about the heritable unit for transmission of biological traits. For other uses, see Gene (disambiguation).

A gene is a locus (or region) of DNA which is made up of nucleotides and is the molecular unit of heredity.[1][2]:Glossary The transmission of genes to an organism’s offspring is the basis of the inheritance of phenotypic traits. Most biological traits are under the influence of polygenes (many different genes) as well as geneenvironment interactions. Some genetic traits are instantly visible, such as eye colour or number of limbs, and some are not, such as blood type, risk for specific diseases, or the thousands of basic biochemical processes that comprise life.

Genes can acquire mutations in their sequence, leading to different variants, known as alleles, in the population. These alleles encode slightly different versions of a protein, which cause different phenotype traits. Colloquial usage of the term “having a gene” (e.g., “good genes,” “hair colour gene”) typically refers to having a different allele of the gene. Genes evolve due to natural selection or survival of the fittest of the alleles.

The concept of a gene continues to be refined as new phenomena are discovered.[3] For example, regulatory regions of a gene can be far removed from its coding regions, and coding regions can be split into several exons. Some viruses store their genome in RNA instead of DNA and some gene products are functional non-coding RNAs. Therefore, a broad, modern working definition of a gene is any discrete locus of heritable, genomic sequence which affect an organism’s traits by being expressed as a functional product or by regulation of gene expression.[4][5]

The existence of discrete inheritable units was first suggested by Gregor Mendel (18221884).[6] From 1857 to 1864, he studied inheritance patterns in 8000 common edible pea plants, tracking distinct traits from parent to offspring. He described these mathematically as 2ncombinations where n is the number of differing characteristics in the original peas. Although he did not use the term gene, he explained his results in terms of discrete inherited units that give rise to observable physical characteristics. This description prefigured the distinction between genotype (the genetic material of an organism) and phenotype (the visible traits of that organism). Mendel was also the first to demonstrate independent assortment, the distinction between dominant and recessive traits, the distinction between a heterozygote and homozygote, and the phenomenon of discontinuous inheritance.

Prior to Mendel’s work, the dominant theory of heredity was one of blending inheritance, which suggested that each parent contributed fluids to the fertilisation process and that the traits of the parents blended and mixed to produce the offspring. Charles Darwin developed a theory of inheritance he termed pangenesis, from Greek pan (“all, whole”) and genesis (“birth”) / genos (“origin”).[7][8] Darwin used the term gemmule to describe hypothetical particles that would mix during reproduction.

Mendel’s work went largely unnoticed after its first publication in 1866, but was rediscovered in the late 19th century by Hugo de Vries, Carl Correns, and Erich von Tschermak, who (claimed to have) reached similar conclusions in their own research.[9] Specifically, in 1889, Hugo de Vries published his book Intracellular Pangenesis,[10] in which he postulated that different characters have individual hereditary carriers and that inheritance of specific traits in organisms comes in particles. De Vries called these units “pangenes” (Pangens in German), after Darwin’s 1868 pangenesis theory.

Sixteen years later, in 1905, the word genetics was first used by William Bateson,[11] while Eduard Strasburger, amongst others, still used the term pangene for the fundamental physical and functional unit of heredity.[12] In 1909 the Danish botanist Wilhelm Johannsen shortened the name to “gene”. [13]

Advances in understanding genes and inheritance continued throughout the 20th century. Deoxyribonucleic acid (DNA) was shown to be the molecular repository of genetic information by experiments in the 1940s to 1950s.[14][15] The structure of DNA was studied by Rosalind Franklin and Maurice Wilkins using X-ray crystallography, which led James D. Watson and Francis Crick to publish a model of the double-stranded DNA molecule whose paired nucleotide bases indicated a compelling hypothesis for the mechanism of genetic replication.[16][17]

In the early 1950s the prevailing view was that the genes in a chromosome acted like discrete entities, indivisible by recombination and arranged like beads on a string. The experiments of Benzer using mutants defective in the rII region of bacteriophage T4 (1955-1959) showed that individual genes have a simple linear structure and are likely to be equivalent to a linear section of DNA.[18][19]

Collectively, this body of research established the central dogma of molecular biology, which states that proteins are translated from RNA, which is transcribed from DNA. This dogma has since been shown to have exceptions, such as reverse transcription in retroviruses. The modern study of genetics at the level of DNA is known as molecular genetics.

In 1972, Walter Fiers and his team at the University of Ghent were the first to determine the sequence of a gene: the gene for Bacteriophage MS2 coat protein.[20] The subsequent development of chain-termination DNA sequencing in 1977 by Frederick Sanger improved the efficiency of sequencing and turned it into a routine laboratory tool.[21] An automated version of the Sanger method was used in early phases of the Human Genome Project.[22]

The theories developed in the 1930s and 1940s to integrate molecular genetics with Darwinian evolution are called the modern evolutionary synthesis, a term introduced by Julian Huxley.[23] Evolutionary biologists subsequently refined this concept, such as George C. Williams’ gene-centric view of evolution. He proposed an evolutionary concept of the gene as a unit of natural selection with the definition: “that which segregates and recombines with appreciable frequency.”[24]:24 In this view, the molecular gene transcribes as a unit, and the evolutionary gene inherits as a unit. Related ideas emphasizing the centrality of genes in evolution were popularized by Richard Dawkins.[25][26]

The vast majority of living organisms encode their genes in long strands of DNA (deoxyribonucleic acid). DNA consists of a chain made from four types of nucleotide subunits, each composed of: a five-carbon sugar (2′-deoxyribose), a phosphate group, and one of the four bases adenine, cytosine, guanine, and thymine.[2]:2.1

Two chains of DNA twist around each other to form a DNA double helix with the phosphate-sugar backbone spiralling around the outside, and the bases pointing inwards with adenine base pairing to thymine and guanine to cytosine. The specificity of base pairing occurs because adenine and thymine align to form two hydrogen bonds, whereas cytosine and guanine form three hydrogen bonds. The two strands in a double helix must therefore be complementary, with their sequence of bases matching such that the adenines of one strand are paired with the thymines of the other strand, and so on.[2]:4.1

Due to the chemical composition of the pentose residues of the bases, DNA strands have directionality. One end of a DNA polymer contains an exposed hydroxyl group on the deoxyribose; this is known as the 3’end of the molecule. The other end contains an exposed phosphate group; this is the 5’end. The two strands of a double-helix run in opposite directions. Nucleic acid synthesis, including DNA replication and transcription occurs in the 5’3’direction, because new nucleotides are added via a dehydration reaction that uses the exposed 3’hydroxyl as a nucleophile.[27]:27.2

The expression of genes encoded in DNA begins by transcribing the gene into RNA, a second type of nucleic acid that is very similar to DNA, but whose monomers contain the sugar ribose rather than deoxyribose. RNA also contains the base uracil in place of thymine. RNA molecules are less stable than DNA and are typically single-stranded. Genes that encode proteins are composed of a series of three-nucleotide sequences called codons, which serve as the “words” in the genetic “language”. The genetic code specifies the correspondence during protein translation between codons and amino acids. The genetic code is nearly the same for all known organisms.[2]:4.1

The total complement of genes in an organism or cell is known as its genome, which may be stored on one or more chromosomes. A chromosome consists of a single, very long DNA helix on which thousands of genes are encoded.[2]:4.2 The region of the chromosome at which a particular gene is located is called its locus. Each locus contains one allele of a gene; however, members of a population may have different alleles at the locus, each with a slightly different gene sequence.

The majority of eukaryotic genes are stored on a set of large, linear chromosomes. The chromosomes are packed within the nucleus in complex with storage proteins called histones to form a unit called a nucleosome. DNA packaged and condensed in this way is called chromatin.[2]:4.2 The manner in which DNA is stored on the histones, as well as chemical modifications of the histone itself, regulate whether a particular region of DNA is accessible for gene expression. In addition to genes, eukaryotic chromosomes contain sequences involved in ensuring that the DNA is copied without degradation of end regions and sorted into daughter cells during cell division: replication origins, telomeres and the centromere.[2]:4.2 Replication origins are the sequence regions where DNA replication is initiated to make two copies of the chromosome. Telomeres are long stretches of repetitive sequence that cap the ends of the linear chromosomes and prevent degradation of coding and regulatory regions during DNA replication. The length of the telomeres decreases each time the genome is replicated and has been implicated in the aging process.[29] The centromere is required for binding spindle fibres to separate sister chromatids into daughter cells during cell division.[2]:18.2

Prokaryotes (bacteria and archaea) typically store their genomes on a single large, circular chromosome. Similarly, some eukaryotic organelles contain a remnant circular chromosome with a small number of genes.[2]:14.4 Prokaryotes sometimes supplement their chromosome with additional small circles of DNA called plasmids, which usually encode only a few genes and are transferable between individuals. For example, the genes for antibiotic resistance are usually encoded on bacterial plasmids and can be passed between individual cells, even those of different species, via horizontal gene transfer.[30]

Whereas the chromosomes of prokaryotes are relatively gene-dense, those of eukaryotes often contain regions of DNA that serve no obvious function. Simple single-celled eukaryotes have relatively small amounts of such DNA, whereas the genomes of complex multicellular organisms, including humans, contain an absolute majority of DNA without an identified function.[31] This DNA has often been referred to as “junk DNA”. However, more recent analyses suggest that, although protein-coding DNA makes up barely 2% of the human genome, about 80% of the bases in the genome may be expressed, so the term “junk DNA” may be a misnomer.[5]

The structure of a gene consists of many elements of which the actual protein coding sequence is often only a small part. These include DNA regions that are not transcribed as well as untranslated regions of the RNA.

Firstly, flanking the open reading frame, all genes contain a regulatory sequence that is required for their expression. In order to be expressed, genes require a promoter sequence. The promoter is recognized and bound by transcription factors and RNA polymerase to initiate transcription.[2]:7.1 A gene can have more than one promoter, resulting in messenger RNAs (mRNA) that differ in how far they extend in the 5’end.[32] Promoter regions have a consensus sequence, however highly transcribed genes have “strong” promoter sequences that bind the transcription machinery well, whereas others have “weak” promoters that bind poorly and initiate transcription less frequently.[2]:7.2Eukaryotic promoter regions are much more complex and difficult to identify than prokaryotic promoters.[2]:7.3

Additionally, genes can have regulatory regions many kilobases upstream or downstream of the open reading frame. These act by binding to transcription factors which then cause the DNA to loop so that the regulatory sequence (and bound transcription factor) become close to the RNA polymerase binding site.[33] For example, enhancers increase transcription by binding an activator protein which then helps to recruit the RNA polymerase to the promoter; conversely silencers bind repressor proteins and make the DNA less available for RNA polymerase.[34]

The transcribed pre-mRNA contains untranslated regions at both ends which contain a ribosome binding site, terminator and start and stop codons.[35] In addition, most eukaryotic open reading frames contain untranslated introns which are removed before the exons are translated. The sequences at the ends of the introns, dictate the splice sites to generate the final mature mRNA which encodes the protein or RNA product.[36]

Many prokaryotic genes are organized into operons, with multiple protein-coding sequences that are transcribed as a unit.[37][38] The genes in an operon are transcribed as a continuous messenger RNA, referred to as a polycistronic mRNA. The term cistron in this context is equivalent to gene. The transcription of an operons mRNA is often controlled by a repressor that can occur in an active or inactive state depending on the presence of certain specific metabolites.[39] When active, the repressor binds to a DNA sequence at the beginning of the operon, called the operator region, and represses transcription of the operon; when the repressor is inactive transcription of the operon can occur (see e.g. Lac operon). The products of operon genes typically have related functions and are involved in the same regulatory network.[2]:7.3

Defining exactly what section of a DNA sequence comprises a gene is difficult.[3]Regulatory regions of a gene such as enhancers do not necessarily have to be close to the coding sequence on the linear molecule because the intervening DNA can be looped out to bring the gene and its regulatory region into proximity. Similarly, a gene’s introns can be much larger than its exons. Regulatory regions can even be on entirely different chromosomes and operate in trans to allow regulatory regions on one chromosome to come in contact with target genes on another chromosome.[40][41]

Early work in molecular genetics suggested the concept that one gene makes one protein. This concept (originally called the one gene-one enzyme hypothesis) emerged from an influential 1941 paper by George Beadle and Edward Tatum on experiments with mutants of the fungus Neurospora crassa.[42]Norman Horowitz, an early colleague on the Neurospora research, reminisced in 2004 that these experiments founded the science of what Beadle and Tatum called biochemical genetics. In actuality they proved to be the opening gun in what became molecular genetics and all the developments that have followed from that.[43] The one gene-one protein concept has been refined since the discovery of genes that can encode multiple proteins by alternative splicing and coding sequences split in short section across the genome whose mRNAs are concatenated by trans-splicing.[5][44][45]

A broad operational definition is sometimes used to encompass the complexity of these diverse phenomena, where a gene is defined as a union of genomic sequences encoding a coherent set of potentially overlapping functional products.[11] This definition categorizes genes by their functional products (proteins or RNA) rather than their specific DNA loci, with regulatory elements classified as gene-associated regions.[11]

In all organisms, two steps are required to read the information encoded in a gene’s DNA and produce the protein it specifies. First, the gene’s DNA is transcribed to messenger RNA (mRNA).[2]:6.1 Second, that mRNA is translated to protein.[2]:6.2 RNA-coding genes must still go through the first step, but are not translated into protein.[46] The process of producing a biologically functional molecule of either RNA or protein is called gene expression, and the resulting molecule is called a gene product.

The nucleotide sequence of a gene’s DNA specifies the amino acid sequence of a protein through the genetic code. Sets of three nucleotides, known as codons, each correspond to a specific amino acid.[2]:6 The principle that three sequential bases of DNA code for each amino acid was demonstrated in 1961 using frameshift mutations in the rIIB gene of bacteriophage T4[47] (see Crick, Brenner et al. experiment).

Additionally, a “start codon”, and three “stop codons” indicate the beginning and end of the protein coding region. There are 64possible codons (four possible nucleotides at each of three positions, hence 43possible codons) and only 20standard amino acids; hence the code is redundant and multiple codons can specify the same amino acid. The correspondence between codons and amino acids is nearly universal among all known living organisms.[48]

Transcription produces a single-stranded RNA molecule known as messenger RNA, whose nucleotide sequence is complementary to the DNA from which it was transcribed.[2]:6.1 The mRNA acts as an intermediate between the DNA gene and its final protein product. The gene’s DNA is used as a template to generate a complementary mRNA. The mRNA matches the sequence of the gene’s DNA coding strand because it is synthesised as the complement of the template strand. Transcription is performed by an enzyme called an RNA polymerase, which reads the template strand in the 3′ to 5’direction and synthesizes the RNA from 5′ to 3′. To initiate transcription, the polymerase first recognizes and binds a promoter region of the gene. Thus, a major mechanism of gene regulation is the blocking or sequestering the promoter region, either by tight binding by repressor molecules that physically block the polymerase, or by organizing the DNA so that the promoter region is not accessible.[2]:7

In prokaryotes, transcription occurs in the cytoplasm; for very long transcripts, translation may begin at the 5’end of the RNA while the 3’end is still being transcribed. In eukaryotes, transcription occurs in the nucleus, where the cell’s DNA is stored. The RNA molecule produced by the polymerase is known as the primary transcript and undergoes post-transcriptional modifications before being exported to the cytoplasm for translation. One of the modifications performed is the splicing of introns which are sequences in the transcribed region that do not encode protein. Alternative splicing mechanisms can result in mature transcripts from the same gene having different sequences and thus coding for different proteins. This is a major form of regulation in eukaryotic cells and also occurs in some prokaryotes.[2]:7.5[49]

Translation is the process by which a mature mRNA molecule is used as a template for synthesizing a new protein.[2]:6.2 Translation is carried out by ribosomes, large complexes of RNA and protein responsible for carrying out the chemical reactions to add new amino acids to a growing polypeptide chain by the formation of peptide bonds. The genetic code is read three nucleotides at a time, in units called codons, via interactions with specialized RNA molecules called transfer RNA (tRNA). Each tRNA has three unpaired bases known as the anticodon that are complementary to the codon it reads on the mRNA. The tRNA is also covalently attached to the amino acid specified by the complementary codon. When the tRNA binds to its complementary codon in an mRNA strand, the ribosome attaches its amino acid cargo to the new polypeptide chain, which is synthesized from amino terminus to carboxyl terminus. During and after synthesis, most new proteins must fold to their active three-dimensional structure before they can carry out their cellular functions.[2]:3

Genes are regulated so that they are expressed only when the product is needed, since expression draws on limited resources.[2]:7 A cell regulates its gene expression depending on its external environment (e.g. available nutrients, temperature and other stresses), its internal environment (e.g. cell division cycle, metabolism, infection status), and its specific role if in a multicellular organism. Gene expression can be regulated at any step: from transcriptional initiation, to RNA processing, to post-translational modification of the protein. The regulation of lactose metabolism genes in E. coli (lac operon) was the first such mechanism to be described in 1961.[50]

A typical protein-coding gene is first copied into RNA as an intermediate in the manufacture of the final protein product.[2]:6.1 In other cases, the RNA molecules are the actual functional products, as in the synthesis of ribosomal RNA and transfer RNA. Some RNAs known as ribozymes are capable of enzymatic function, and microRNA has a regulatory role. The DNA sequences from which such RNAs are transcribed are known as non-coding RNA genes.[46]

Some viruses store their entire genomes in the form of RNA, and contain no DNA at all.[51][52] Because they use RNA to store genes, their cellular hosts may synthesize their proteins as soon as they are infected and without the delay in waiting for transcription.[53] On the other hand, RNA retroviruses, such as HIV, require the reverse transcription of their genome from RNA into DNA before their proteins can be synthesized. RNA-mediated epigenetic inheritance has also been observed in plants and very rarely in animals.[54]

Organisms inherit their genes from their parents. Asexual organisms simply inherit a complete copy of their parent’s genome. Sexual organisms have two copies of each chromosome because they inherit one complete set from each parent.[2]:1

According to Mendelian inheritance, variations in an organism’s phenotype (observable physical and behavioral characteristics) are due in part to variations in its genotype (particular set of genes). Each gene specifies a particular trait with different sequence of a gene (alleles) giving rise to different phenotypes. Most eukaryotic organisms (such as the pea plants Mendel worked on) have two alleles for each trait, one inherited from each parent.[2]:20

Alleles at a locus may be dominant or recessive; dominant alleles give rise to their corresponding phenotypes when paired with any other allele for the same trait, whereas recessive alleles give rise to their corresponding phenotype only when paired with another copy of the same allele. For example, if the allele specifying tall stems in pea plants is dominant over the allele specifying short stems, then pea plants that inherit one tall allele from one parent and one short allele from the other parent will also have tall stems. Mendel’s work demonstrated that alleles assort independently in the production of gametes, or germ cells, ensuring variation in the next generation. Although Mendelian inheritance remains a good model for many traits determined by single genes (including a number of well-known genetic disorders) it does not include the physical processes of DNA replication and cell division.[55][56]

The growth, development, and reproduction of organisms relies on cell division, or the process by which a single cell divides into two usually identical daughter cells. This requires first making a duplicate copy of every gene in the genome in a process called DNA replication.[2]:5.2 The copies are made by specialized enzymes known as DNA polymerases, which “read” one strand of the double-helical DNA, known as the template strand, and synthesize a new complementary strand. Because the DNA double helix is held together by base pairing, the sequence of one strand completely specifies the sequence of its complement; hence only one strand needs to be read by the enzyme to produce a faithful copy. The process of DNA replication is semiconservative; that is, the copy of the genome inherited by each daughter cell contains one original and one newly synthesized strand of DNA.[2]:5.2

The rate of DNA replication in living cells was first measured as the rate of phage T4 DNA elongation in phage-infected E. coli and found to be impressively rapid.[57] During the period of exponential DNA increase at 37 C, the rate of elongation was 749 nucleotides per second.

After DNA replication is complete, the cell must physically separate the two copies of the genome and divide into two distinct membrane-bound cells.[2]:18.2 In prokaryotes(bacteria and archaea) this usually occurs via a relatively simple process called binary fission, in which each circular genome attaches to the cell membrane and is separated into the daughter cells as the membrane invaginates to split the cytoplasm into two membrane-bound portions. Binary fission is extremely fast compared to the rates of cell division in eukaryotes. Eukaryotic cell division is a more complex process known as the cell cycle; DNA replication occurs during a phase of this cycle known as S phase, whereas the process of segregating chromosomes and splitting the cytoplasm occurs during M phase.[2]:18.1

The duplication and transmission of genetic material from one generation of cells to the next is the basis for molecular inheritance, and the link between the classical and molecular pictures of genes. Organisms inherit the characteristics of their parents because the cells of the offspring contain copies of the genes in their parents’ cells. In asexually reproducing organisms, the offspring will be a genetic copy or clone of the parent organism. In sexually reproducing organisms, a specialized form of cell division called meiosis produces cells called gametes or germ cells that are haploid, or contain only one copy of each gene.[2]:20.2 The gametes produced by females are called eggs or ova, and those produced by males are called sperm. Two gametes fuse to form a diploid fertilized egg, a single cell that has two sets of genes, with one copy of each gene from the mother and one from the father.[2]:20

During the process of meiotic cell division, an event called genetic recombination or crossing-over can sometimes occur, in which a length of DNA on one chromatid is swapped with a length of DNA on the corresponding homologous non-sister chromatid. This can result in reassortment of otherwise linked alleles.[2]:5.5 The Mendelian principle of independent assortment asserts that each of a parent’s two genes for each trait will sort independently into gametes; which allele an organism inherits for one trait is unrelated to which allele it inherits for another trait. This is in fact only true for genes that do not reside on the same chromosome, or are located very far from one another on the same chromosome. The closer two genes lie on the same chromosome, the more closely they will be associated in gametes and the more often they will appear together; genes that are very close are essentially never separated because it is extremely unlikely that a crossover point will occur between them. This is known as genetic linkage.[58]

DNA replication is for the most part extremely accurate, however errors (mutations) do occur.[2]:7.6 The error rate in eukaryotic cells can be as low as 108 per nucleotide per replication,[59][60] whereas for some RNA viruses it can be as high as 103.[61] This means that each generation, each human genome accumulates 12 new mutations.[61] Small mutations can be caused by DNA replication and the aftermath of DNA damage and include point mutations in which a single base is altered and frameshift mutations in which a single base is inserted or deleted. Either of these mutations can change the gene by missense (change a codon to encode a different amino acid) or nonsense (a premature stop codon).[62] Larger mutations can be caused by errors in recombination to cause chromosomal abnormalities including the duplication, deletion, rearrangement or inversion of large sections of a chromosome. Additionally, DNA repair mechanisms can introduce mutational errors when repairing physical damage to the molecule. The repair, even with mutation, is more important to survival than restoring an exact copy, for example when repairing double-strand breaks.[2]:5.4

When multiple different alleles for a gene are present in a species’s population it is called polymorphic. Most different alleles are functionally equivalent, however some alleles can give rise to different phenotypic traits. A gene’s most common allele is called the wild type, and rare alleles are called mutants. The genetic variation in relative frequencies of different alleles in a population is due to both natural selection and genetic drift.[63] The wild-type allele is not necessarily the ancestor of less common alleles, nor is it necessarily fitter.

Most mutations within genes are neutral, having no effect on the organism’s phenotype (silent mutations). Some mutations do not change the amino acid sequence because multiple codons encode the same amino acid (synonymous mutations). Other mutations can be neutral if they lead to amino acid sequence changes, but the protein still functions similarly with the new amino acid (e.g. conservative mutations). Many mutations, however, are deleterious or even lethal, and are removed from populations by natural selection. Genetic disorders are the result of deleterious mutations and can be due to spontaneous mutation in the affected individual, or can be inherited. Finally, a small fraction of mutations are beneficial, improving the organism’s fitness and are extremely important for evolution, since their directional selection leads to adaptive evolution.[2]:7.6

Genes with a most recent common ancestor, and thus a shared evolutionary ancestry, are known as homologs.[64] These genes appear either from gene duplication within an organism’s genome, where they are known as paralogous genes, or are the result of divergence of the genes after a speciation event, where they are known as orthologous genes,[2]:7.6 and often perform the same or similar functions in related organisms. It is often assumed that the functions of orthologous genes are more similar than those of paralogous genes, although the difference is minimal.[65][66]

The relationship between genes can be measured by comparing the sequence alignment of their DNA.[2]:7.6 The degree of sequence similarity between homologous genes is called conserved sequence. Most changes to a gene’s sequence do not affect its function and so genes accumulate mutations over time by neutral molecular evolution. Additionally, any selection on a gene will cause its sequence to diverge at a different rate. Genes under stabilizing selection are constrained and so change more slowly whereas genes under directional selection change sequence more rapidly.[67] The sequence differences between genes can be used for phylogenetic analyses to study how those genes have evolved and how the organisms they come from are related.[68][69]

The most common source of new genes in eukaryotic lineages is gene duplication, which creates copy number variation of an existing gene in the genome.[70][71] The resulting genes (paralogs) may then diverge in sequence and in function. Sets of genes formed in this way comprise a gene family. Gene duplications and losses within a family are common and represent a major source of evolutionary biodiversity.[72] Sometimes, gene duplication may result in a nonfunctional copy of a gene, or a functional copy may be subject to mutations that result in loss of function; such nonfunctional genes are called pseudogenes.[2]:7.6

“Orphan” genes, whose sequence shows no similarity to existing genes, are less common than gene duplicates. Estimates of the number of genes with no homologs outside humans range from 18[73] to 60.[74] Two primary sources of orphan protein-coding genes are gene duplication followed by extremely rapid sequence change, such that the original relationship is undetectable by sequence comparisons, and de novo conversion of a previously non-coding sequence into a protein-coding gene.[75] De novo genes are typically shorter and simpler in structure than most eukaryotic genes, with few if any introns.[70] Over long evolutionary time periods, de novo gene birth may be responsible for a significant fraction of taxonomically-restricted gene families.[76]

Horizontal gene transfer refers to the transfer of genetic material through a mechanism other than reproduction. This mechanism is a common source of new genes in prokaryotes, sometimes thought to contribute more to genetic variation than gene duplication.[77] It is a common means of spreading antibiotic resistance, virulence, and adaptive metabolic functions.[30][78] Although horizontal gene transfer is rare in eukaryotes, likely examples have been identified of protist and alga genomes containing genes of bacterial origin.[79][80]

The genome is the total genetic material of an organism and includes both the genes and non-coding sequences.[81]

The genome size, and the number of genes it encodes varies widely between organisms. The smallest genomes occur in viruses (which can have as few as 2 protein-coding genes),[90] and viroids (which act as a single non-coding RNA gene).[91] Conversely, plants can have extremely large genomes,[92] with rice containing >46,000 protein-coding genes.[93] The total number of protein-coding genes (the Earth’s proteome) is estimated to be 5million sequences.[94]

Although the number of base-pairs of DNA in the human genome has been known since the 1960s, the estimated number of genes has changed over time as definitions of genes, and methods of detecting them have been refined. Initial theoretical predictions of the number of human genes were as high as 2,000,000.[95] Early experimental measures indicated there to be 50,000100,000 transcribed genes (expressed sequence tags).[96] Subsequently, the sequencing in the Human Genome Project indicated that many of these transcripts were alternative variants of the same genes, and the total number of protein-coding genes was revised down to ~20,000[89] with 13 genes encoded on the mitochondrial genome.[87] Of the human genome, only 12% consists of protein-coding genes,[97] with the remainder being ‘noncoding’ DNA such as introns, retrotransposons, and noncoding RNAs.[97][98] Every multicellular organism has all its genes in each cell of its body but not every gene functions in every cell .

Essential genes are the set of genes thought to be critical for an organism’s survival.[100] This definition assumes the abundant availability of all relevant nutrients and the absence of environmental stress. Only a small portion of an organism’s genes are essential. In bacteria, an estimated 250400 genes are essential for Escherichia coli and Bacillus subtilis, which is less than 10% of their genes.[101][102][103] Half of these genes are orthologs in both organisms and are largely involved in protein synthesis.[103] In the budding yeast Saccharomyces cerevisiae the number of essential genes is slightly higher, at 1000 genes (~20% of their genes).[104] Although the number is more difficult to measure in higher eukaryotes, mice and humans are estimated to have around 2000 essential genes (~10% of their genes).[105] The synthetic organism, Syn 3, has a minimal genome of 473 essential genes and quasi-essential genes (necessary for fast growth), although 149 have unknown function.[99]

Essential genes include Housekeeping genes (critical for basic cell functions)[106] as well as genes that are expressed at different times in the organisms development or life cycle.[107] Housekeeping genes are used as experimental controls when analysing gene expression, since they are constitutively expressed at a relatively constant level.

Gene nomenclature has been established by the HUGO Gene Nomenclature Committee (HGNC) for each known human gene in the form of an approved gene name and symbol (short-form abbreviation), which can be accessed through a database maintained by HGNC. Symbols are chosen to be unique, and each gene has only one symbol (although approved symbols sometimes change). Symbols are preferably kept consistent with other members of a gene family and with homologs in other species, particularly the mouse due to its role as a common model organism.[108]

Genetic engineering is the modification of an organism’s genome through biotechnology. Since the 1970s, a variety of techniques have been developed to specifically add, remove and edit genes in an organism.[109] Recently developed genome engineering techniques use engineered nuclease enzymes to create targeted DNA repair in a chromosome to either disrupt or edit a gene when the break is repaired.[110][111][112][113] The related term synthetic biology is sometimes used to refer to extensive genetic engineering of an organism.[114]

Genetic engineering is now a routine research tool with model organisms. For example, genes are easily added to bacteria[115] and lineages of knockout mice with a specific gene’s function disrupted are used to investigate that gene’s function.[116][117] Many organisms have been genetically modified for applications in agriculture, industrial biotechnology, and medicine.

For multicellular organisms, typically the embryo is engineered which grows into the adult genetically modified organism.[118] However, the genomes of cells in an adult organism can be edited using gene therapy techniques to treat genetic diseases.

Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). Molecular Biology of the Cell (Fourth ed.). New York: Garland Science. ISBN978-0-8153-3218-3. A molecular biology textbook available free online through NCBI Bookshelf.

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Gene – Wikipedia

Recommendation and review posted by Bethany Smith

Could gene therapy become biotechs growth driver in 2017 …

Despite bouncing off a 2-year low, biotech is still an unpopular sector and investors are rightfully concerned about its near-term prospects. Recent drug failures, growing pricing pressure and the potential impact of biosimilars all contribute to the negative sentiment, but the main problem is the lack of growth drivers for the remainder of 2016 (and potentially 2017).

The biotech industry relies on innovation cycles to create new revenue sources. This was the case in the 2013-2014 biotech bull market, which was driven by a wave of medical breakthroughs (PD-1, HCV, CAR/TCR, oral MS drugs, CF etc.). These waves typically involve new therapeutic approaches coupled with disruptive technologies as their enablers.

In oncology, for example, the understanding that cancer is driven by aberrant signaling coupled with advances in medicinal chemistry and antibody engineering led to the development of kinase inhibitors and monoclonal antibodies as blockers of signaling. A decade later, insights around cancer immunology gave rise to the immuno-oncology field and PD-1 inhibitors in particular, which are expected to become the biggest oncology franchise ever.

Gene therapy ticks all the boxes

While there are several hot areas in biotech such as gene editing and microbiome, most are still early and their applicability is unclear. Gene therapy, on the other hand, is more mature and de-risked with tens of clinical studies and the potential to treat (and perhaps cure) a wide range of diseases where treatment is inadequate or non-existent. The commercial upside from these programs is huge and should expand as additional indications are pursued.

As I previously discussed, the past two years saw a surge in the number of clinical-stage gene therapies, some of which already generated impressive efficacy across multiple indications. This makes gene therapy the only truly disruptive field which is mature enough not only from a technology but also from a clinical standpoint. Importantly, most studies are conducted by companies according to industry and regulatory standards, in contrast to historical gene therapy studies that were run by academic groups.

To me, the striking thing about the results is the breadth of technologies, indications and modes of administrations evaluated to date. This versatility is very important for the future of gene therapy as it reduces overall development risk and increases likelihood of success by allowing companies to tailor the right product for each indication. Parameters include mode of administration (local vs. systemic vs. ex vivo), tropism for the target tissue (eye, bone marrow, liver etc.), immunogenicity and onset of activity.

Building a diversified gene therapy basket

Given the early development stage and large number of technologies, I prefer to own a basket of gene therapy stocks with a focus on the more clinically validated ones: Spark (ONCE), Bluebird (BLUE) and Avexis (AVXS).

Bluebird and Spark are the most further along (and also the largest based on market cap) gene therapy companies and should be the basis for any gene therapy portfolio. With two completely different technologies, the two companies have strong clinical proof-of-concept for their respective lead programs.

Avexis is less advanced without a clinically validated product, but recent data for its lead program are too promising to ignore.

Spark Clinical validation for retinal and liver indications

Sparks lead programs (SPK-RPE65) will probably become the first gene therapy to get FDA approval. In October, the company reported strong P3 data in rare genetic retinal conditions caused by RPE65 mutations, the first randomized and statistically significant data for a gene therapy. The company is expected to complete its BLA submission later in 2016 which should lead to FDA approval in 2017. Sparks second ophthalmology program for choroideremia is in P1 with efficacy data expected later in 2016.

Earlier this month, Spark released an encouraging update for its Hemophilia B program, SPK-9001 (partnered with Pfizer [PFE]). A single administration of SPK-9001 led to a sustained and clinically meaningful production of Factor IX, a clotting factor which is dysfunctional in Hemophilia B patients. All four treated patients experienced a clinically significant increase in Factor IX activity from

Spark intends to advance its wholly-owned Hemophilia A program (SPK-8011) to the clinic later in 2016 with initial data expected in H1:2017. Results in the Hemophilia B should be viewed as a positive read-through but Hemophilia A still presents certain technical challenges (e.g. missing protein is several fold larger) which required Spark to use a different vector. Hemophilia A represents a $5B opportunity compared to $1B for Hemophilia B.


Despite being one of the worst biotech performers, Bluebird remains the largest and most visible gene therapy company. In contrast to most gene therapy companies, Bluebird treats patients cells ex-vivo (outside of the body) in a process that resembles stem cell transplant or adoptive cell transfer (CAR, TCR). Progenitor cells are collected from the patient, a genetic modification is integrated into the genome followed by infusion of the cells that repopulate the bone marrow. This enables Bluebird to go after hematologic diseases like beta thalassemia and Sickle-cell disease (SCD) where target cells are constantly dividing.

Sentiment around Bluebirds lead program, Lenti-globin , plummeted last year after a series of disappointing results in a subset of beta-thal patients and preliminary data in SCD, which represents the more important commercial opportunity. Particularly in SCD patients, post-treatment hemoglobin levels were relatively low and although some increase has been noted with time, it is still unclear what the maximal effect would be. Market reaction was brutal, sending shares down 75% in just over a year.

Next update for Lenti-globin is expected at ASH in December. Despite the disappointing efficacy observed in SCD and beta-thal, I am cautiously optimistic about Bluebirds efforts to optimize treatment protocols and regimens. These include specific conditioning regimens and ex-vivo treatment of cells that may improve transduction rate and hemoglobin production in patients. Some of these modifications are already being implemented in newly recruited patients and hopefully longer follow up will lead to higher hemoglobin levels in already-reported patients.

The only clinical update so far in 2016 was for Lenti-D in C-ALD, a rare neurological disease that affects infants in their first years. Results demonstrated that of 17 patients treated to date (median follow-up of 16 months), all remain alive and free of major functional deterioration (defined as major functional disabilities, MFD). The primary endpoint, defined as no MFD at 2 years, was reached for 3/3 patients with sufficient follow-up and assuming the trend continues Bluebird may be in a position to file for approval in H2:2017.

Lenti-Ds commercial opportunity is limited (200 patients diagnosed each year in developed countries) so investors understandably focus on Lenti-globin, which is being developed for beta thal (~20k patients in developed countries) and SCD (~160k patients).

Bluebird is expected to end 2016 with ~$650M in cash. Current market cap is $1.7B.


Avexis is developing AVXS-101 for Spinal muscular atrophy Type 1 (SMA1), a rapidly deteriorating and fatal neuro-muscular disease. SMA1 is characterized by rapid deterioration in motor and neuronal functions with 50% of patients experiencing death or permanent ventilation by their first anniversary. Most patients die from respiratory failure by the age of two. SMA Type 2 and Type 3 are also caused by SMN1 mutations and are characterized by a later onset and milder disease burden (but unmet need is still significant in these indications). The US prevalence of SMA is 10,000, 600 of which are SMA1.

In contrast to Bluebird and Spark, Avexis does not have conclusive proof it can lead to expression of the missing protein (SMN1) in the target tissue nor does it have randomized clinical data but the results generated to date are simply too provocative to ignore.

At the most recent update, Avexis presented data for 15 patients who received AVXS-101 in their first months of life. 3 patients were treated with a low dose and 12 were treated with a high dose. Strikingly, none of the children experienced an event (defined as ventilation or death), including patients who reached 2 years of age. All 9 patients with sufficient follow up, reached the age of 13.6 months without an event in contrast to historical data that show an event-free survival of 25%. AVXS-101 also led to a dose dependent increase in motor function which had a quick onset especially at the higher dose.

As with any results from an open label study without a control arm, these data should be analyzed with caution, as they need to be corroborated by large controlled studies (expected to start next year). Still, the data point to an overwhelming benefit in a very aggressive disease. One of the most exciting aspects of this program is the fact that it is given systemically via IV administration, which implies the treatment reaches the neurons in the CNS. Avexis plans to start a trial in SMA2 in H2:16 using intrathecal delivery (directly to the spinal canal). This decision is surprising given the results with IV administration in SMA1 and the fact that the BBB immaturity hypothesis in babies is not considered relevant anymore. (See this review)

AVXS-101s main competitor is Biogens (BIIB) and Ionis (IONS) nusinersen, an antisense molecule that needs to be intrathecally injected 3-4 times a year. As both drugs generated encouraging clinical data in small non-randomized studies, it is hard to compare them, however, AVXS-101 has an obvious advantage of being a potentially one time IV injection. Nusinersen is in P3 with topline data expected in mid-2017.

AVXS-101 is based on an AAV9 vector developed by REGENXBIO (RGNX), which licensed the technology to Avexis. Beyond the 5%-10% in royalties REGENXBIO is eligible to receive, data for AVXS-101 bode well for the companys proprietary programs in MPS-I and MPS-II, two other rare diseases with neurological involvement where BBB penetration is crucial. These programs are also based on REGENXBIOs AAV9.

Beyond AVXS-101, REGENXBIO has an impressive partnered pipeline which includes collaborations with Voyager (VYGR), Dimension (DMTX) , Baxalta and Lysogene.

Portfolio updates Immunogen, Marinus, Esperion

June was a rough month for three of my holdings. Immunogen (IMGN) had a disappointing data set at ASCO, Marinus (MRNS) reported a P3 failure in epilepsy and most recently, Esperion was dealt a regulatory blow from the FDA that may push development timelines by several years. I am selling Immunogen and Marinus due to the lack of near-term catalysts although long-term their respective drugs could still be valuable. I decided to keep Esperion as I still find ETC-1002 very attractive and hope that PCSK9s CVOT data will soften FDAs concerns about LDL-C reduction as an approvable endpoint.

Three additional companies with important binary readouts in the coming months are Array Biopharma (ARRY), SAGE (SAGE) and Aurinia (AUPH). Array will have P3 data for selumetinib (partnered with AstraZeneca) in KRAS+ NSCLC. SAGE will report data from a randomized P2 in PPD following a promising single-arm data set. Aurinia will report results from the AURA study in lupus nephritis patients, where there is a strong rationale for using the companys drug (voclosporin) but limited direct clinical validation.

Portfolio holdings July 4, 2016


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Could gene therapy become biotechs growth driver in 2017 …

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Quantitative genetics – Wikipedia

Quantitative genetics is a branch of population genetics that deals with phenotypes that vary continuously (in characters such as height or mass)as opposed to discretely identifiable phenotypes and gene-products (such as eye-colour, or the presence of a particular biochemical).

Both branches use the frequencies of different alleles of a gene in breeding populations (gamodemes), and combine them with concepts from simple Mendelian inheritance to analyze inheritance patterns across generations and descendant lines. While population genetics can focus on particular genes and their subsequent metabolic products, quantitative genetics focuses more on the outward phenotypes, and makes summaries only of the underlying genetics.

Due to the continuous distribution of phenotypic values, quantitative genetics must employ many other statistical methods (such as the effect size, the mean and the variance) to link phenotypes (attributes) to genotypes. Some phenotypes may be analyzed either as discrete categories or as continuous phenotypes, depending on the definition of cut-off points, or on the metric used to quantify them.[1]:2769 Mendel himself had to discuss this matter in his famous paper,[2] especially with respect to his peas attribute tall/dwarf, which actually was “length of stem”.[3][4] Analysis of quantitative trait loci, or QTL,[5][6][7] is a more recent addition to quantitative genetics, linking it more directly to molecular genetics.

In diploid organisms, the average genotypic “value” (locus value) may be defined by the allele “effect” together with a dominance effect, and also by how genes interact with genes at other loci (epistasis). The founder of quantitative genetics – Sir Ronald Fisher – perceived much of this when he proposed the first mathematics of this branch of genetics.[8]

Being a statistician, he defined the gene effects as deviations from a central valueenabling the use of statistical concepts such as mean and variance, which use this idea.[9] The central value he chose for the gene was the midpoint between the two opposing homozygotes at the one locus. The deviation from there to the “greater” homozygous genotype can be named “+a”; and therefore it is “-a” from that same midpoint to the “lesser” homozygote genotype. This is the “allele” effect mentioned above. The heterozygote deviation from the same midpoint can be named “d”, this being the “dominance” effect referred to above.[10] The diagram depicts the idea. However, in reality we measure phenotypes, and the figure also shows how observed phenotypes relate to the gene effects. Formal definitions of these effects recognize this phenotypic focus.[11][12] Epistasis has been approached statistically as interaction (i.e., inconsistencies),[13] but epigenetics suggests a new approach may be needed.

If 0a was known as “over-dominance”.[14]

Mendel’s pea attribute “length of stem” provides us with a good example.[3] Mendel stated that the tall true-breeding parents ranged from 67 feet in stem length (183 213cm), giving a median of 198cm (= P1). The short parents ranged from 0.75 – 1.25 feet in stem length (23 46cm), with a rounded median of 34cm (= P2). Their hybrid ranged from 67.5 feet in length (183229cm), with a median of 206cm (= F1). The mean of P1 and P2 is 116cm, this being the phenotypic value of the homozygotes midpoint (mp). The allele affect (a) is [P1-mp] = 82cm = -[P2-mp]. The dominance effect (d) is [F1-mp] = 90cm.[15] This historical example illustrates clearly how phenotype values and gene effects are linked.

To obtain means, variances and other statistics, both quantities and their occurrences are required. The gene effects (above) provide the framework for quantities: and the frequencies of the contrasting alleles in the fertilization gamete-pool provide the information on occurrences.

Commonly, the frequency of the allele causing “more” in the phenotype (including dominance) is given the symbol p, while the frequency of the contrasting allele is q. An initial assumption made when establishing the algebra was that the parental population was infinite and random mating, which was made simply to facilitate the derivation. The subsequent mathematical development also implied that the frequency distribution within the effective gamete-pool was uniform: there were no local perturbations where p and q varied. Looking at the diagrammatic analysis of sexual reproduction, this is the same as declaring that pP = pg = p; and similarly for q.[14] This mating system, dependent upon these assumptions, became known as “panmixia”.

Panmixia rarely actually occurs in nature,[16]:152180[17] as gamete distribution may be limited, for example by dispersal restrictions or by behaviour, or by chance sampling (those local perturbations mentioned above). It is well-known that there is a huge wastage of gametes in Nature, which is why the diagram depicts a potential gamete-pool separately to the actual gamete-pool. Only the latter sets the definitive frequencies for the zygotes: this is the true “gamodeme” (“gamo” refers to the gametes, and “deme” derives from Greek for “population”). But, under Fisher’s assumptions, the gamodeme can be effectively extended back to the potential gamete-pool, and even back to the parental base-population (the “source” population). The random sampling arising when small “actual” gamete-pools are sampled from a large “potential” gamete-pool is known as genetic drift, and is considered subsequently.

While panmixia may not be widely extant, the potential for it does occur, although it may be only ephemeral because of those local perturbations. It has been shown, for example, that the F2 derived from random fertilization of F1 individuals (an allogamous F2), following hybridization, is an origin of a new potentially panmictic population.[18][19] It has also been shown that if panmictic random fertilization occurred continually, it would maintain the same allele and genotype frequencies across each successive panmictic sexual generationthis being the Hardy Weinberg equilibrium.[13]:3439[20][21][22][23] However, as soon as genetic drift was initiated by local random sampling of gametes, the equilibrium would cease.

Male and female gametes within the actual fertilizing pool are considered usually to have the same frequencies for their corresponding alleles. (Exceptions have been considered.) This means that when p male gametes carrying the A allele randomly fertilize p female gametes carrying that same allele, the resulting zygote has genotype AA, and, under random fertilization, the combination occurs with a frequency of p x p (= p2). Similarly, the zygote aa occurs with a frequency of q2. Heterozygotes (Aa) can arise in two ways: when p male (A allele) randomly fertilize q female (a allele) gametes, and vice versa. The resulting frequency for the heterozygous zygotes is thus 2pq.[13]:32 Notice that such a population is never more than half heterozygous, this maximum occurring when p=q= 0.5.

In summary then, under random fertilization, the zygote (genotype) frequencies are the quadratic expansion of the gametic (allelic) frequencies: ( p + q ) 2 = p 2 + 2 p q + q 2 = 1 {textstyle (p+q)^{2}=p^{2}+2pq+q^{2}=1} . (The “=1” states that the frequencies are in fraction form, not percentages; and that there are no omissions within the framework proposed.)

Notice that “random fertilization” and “panmixia” are not synonyms.

Mendel’s pea experiments were constructed by establishing true-breeding parents with “opposite” phenotypes for each attribute.[3] This meant that each opposite parent was homozygous for its respective allele only. In our example, “tall vs dwarf”, the tall parent would be genotype TT with p = 1 (and q = 0); while the dwarf parent would be genotype tt with q = 1 (and p = 0). After controlled crossing, their hybrid is Tt, with p = q = . However, the frequency of this heterozygote = 1, because this is the F1 of an artificial cross: it has not arisen through random fertilization.[24] The F2 generation was produced by natural self-pollination of the F1 (with monitoring against insect contamination), resulting in p = q = being maintained. Such an F2 is said to be “autogamous”. However, the genotype frequencies (0.25 TT, 0.5 Tt, 0.25 tt) have arisen through a mating system very different from random fertilization, and therefore the use of the quadratic expansion has been avoided. The numerical values obtained were the same as those for random fertilization only because this is the special case of having originally crossed homozygous opposite parents.[25] We can notice that, because of the dominance of T- [frequency (0.25 + 0.5)] over tt [frequency 0.25], the 3:1 ratio is still obtained.

A cross such as Mendel’s, where true-breeding (largely homozygous) opposite parents are crossed in a controlled way to produce an F1, is a special case of hybrid structure. The F1 is often regarded as “entirely heterozygous” for the gene under consideration. However, this is an over-simplification and does not apply generallyfor example when individual parents are not homozygous, or when populations inter-hybridise to form hybrid swarms.[24] The general properties of intra-species hybrids (F1) and F2 (both “autogamous” and “allogamous”) are considered in a later section.

Having noticed that the pea is naturally self-pollinated, we cannot continue to use it as an example for illustrating random fertilization properties. Self-fertilization (“selfing”) is a major alternative to random fertilization, especially within Plants. Most of the Earth’s cereals are naturally self-pollinated (rice, wheat, barley, for example), as well as the pulses. Considering the millions of individuals of each of these on Earth at any time, it’s obvious that self-fertilization is at least as significant as random fertilization. Self-fertilization is the most intensive form of inbreeding, which arises whenever there is restricted independence in the genetical origins of gametes. Such reduction in independence arises if parents are already related, and/or from genetic drift or other spatial restrictions on gamete dispersal. Path analysis demonstrates that these are tantamount to the same thing.[26][27] Arising from this background, the inbreeding coefficient (often symbolized as F or f) quantifies the effect of inbreeding from whatever cause. There are several formal definitions of f, and some of these are considered in later sections. For the present, note that for a long-term self-fertilized species f = 1. Natural self-fertilized populations are not single ” pure lines “, however, but mixtures of such lines. This becomes particularly obvious when considering more than one gene at a time. Therefore, allele frequencies (p and q) other than 1 or 0 are still relevant in these cases (refer back to the Mendel Cross section). The genotype frequencies take a different form, however.

In general, the genotype frequencies become [ p 2 ( 1 f ) + p f ] {textstyle [p^{2}(1-f)+pf]} for AA and 2 p q ( 1 f ) {textstyle 2pq(1-f)} for Aa and [ q 2 ( 1 f ) + q f ] {textstyle [q^{2}(1-f)+qf]} for aa.[13]:65

Notice that the frequency of the heterozygote declines in proportion to f. When f = 1, these three frequencies become respectively p, 0 and q Conversely, when f = 0, they reduce to the random-fertilization quadratic expansion shown previously.

The population mean shifts the central reference point from the homozygote midpoint (mp) to the mean of a sexually reproduced population. This is important not only to relocate the focus into the natural world, but also to use a measure of central tendency used by Statistics/Biometrics. In particular, the square of this mean is the Correction Factor, which is used to obtain the genotypic variances later.[9]

For each genotype in turn, its allele effect is multiplied by its genotype frequency; and the products are accumulated across all genotypes in the model. Some algebraic simplification usually follows to reach a succinct result.

The contribution of AA is p 2 ( + ) a {textstyle p^{2}(+)a} , that of Aa is 2 p q d {textstyle 2pqd} , and that of aa is q 2 ( ) a {textstyle q^{2}(-)a} . Gathering together the two a terms and accumulating over all, the result is: a ( p 2 q 2 ) + 2 p q d {textstyle a(p^{2}-q^{2})+2pqd} . Simplification is achieved by noting that ( p 2 q 2 ) = ( p q ) ( p + q ) {textstyle (p^{2}-q^{2})=(p-q)(p+q)} , and by recalling that ( p + q ) = 1 {textstyle (p+q)=1} , thereby reducing the right-hand term to ( p q ) {textstyle (p-q)} .

The succinct result is therefore G = a ( p q ) + 2 p q d {textstyle G=a(p-q)+2pqd} .[14]:110

This defines the population mean as an “offset” from the homozygote midpoint (recall a and d are defined as deviations from that midpoint). The Figure depicts G across all values of p for several values of d, including one case of slight over-dominance. Notice that G is often negative, thereby emphasizing that it is itself a deviation (from mp).

Finally, to obtain the actual Population Mean in “phenotypic space”, the midpoint value is added to this offset: P = G + m p {textstyle P=G+mp} .

An example arises from data on ear length in maize.[28]:103 Assuming for now that one gene only is represented, a = 5.45cm, d = 0.12cm [virtually “0”, really], mp = 12.05cm. Further assuming that p = 0.6 and q = 0.4 in this example population, then:

G = 5.45 (0.6 – 0.4) + (0.48)0.12 = 1.15cm (rounded); and

P = 1.15 + 12.05 = 13.20cm (rounded).

The contribution of AA is p ( + a ) {textstyle p(+a)} , while that of aa is q ( a ) {textstyle q(-a)} . [See above for the frequencies.] Gathering these two a terms together leads to an immediately very simple final result:

G ( f = 1 ) = a ( p q ) {textstyle G_{(f=1)}=a(p-q)} . As before, P = G + m p {textstyle P=G+mp} .

Often, “G(f=1)” is abbreviated to “G1”.

Mendel’s peas can provide us with the allele effects and midpoint (see previously); and a mixed self-pollinated population with p = 0.6 and q = 0.4 provides example frequencies. Thus:

G(f=1) = 82 (0.6 – .04) = 59.6cm (rounded); and

P(f=1) = 59.6 + 116 = 175.6cm (rounded).

A general formula incorporates the inbreeding coefficient f, and can then accommodate any situation. The procedure is exactly the same as before, using the weighted genotype frequencies given earlier. After translation into our symbols, and further rearrangement:[13]:7778

G f = a ( q p ) + [ 2 p q d f ( 2 p q d ) ] = a ( p q ) + ( 1 f ) 2 p q d = G 0 f 2 p q d {displaystyle {begin{aligned}G_{f}&=a(q-p)+[2pqd-f(2pqd)]\&=a(p-q)+(1-f)2pqd\&=G_{0}-f 2pqdend{aligned}}}

Supposing that the maize example [given earlier] had been constrained on a holme (a narrow riparian meadow), and had partial inbreeding to the extent of f = 0.25, then, using the third version (above) of Gf:

G0.25 = 1.15 – 0.25 (0.48) 0.12 = 1.136 cm (rounded), with P0.25 = 13.194 cm (rounded).

There is hardly any effect from inbreeding in this example, which arises because there was virtually no dominance in this attribute (d 0). Examination of all three versions of Gf reveals that this would lead to trivial change in the Population mean. Where dominance was notable, however, there would be considerable change.

Genetic drift was introduced when discussing the likelihood of panmixia being widely extant as a natural fertilization pattern. [See section on Allele and Genotype frequencies.] Here the sampling of gametes from the potential gamodeme is discussed in more detail. The sampling involves random fertilization between pairs of random gametes, each of which may contain either an A or an a allele. The sampling is therefore binomial sampling.[13]:382395[14]:4963[29]:35[30]:55 Each sampling “packet” involves 2N alleles, and produces N zygotes (a “progeny” or a “line”) as a result. During the course of the reproductive period, this sampling is repeated over and over, so that the final result is a mixture of sample progenies. The result is dispersed random fertilization ( ) {displaystyle left(bigodot right)} These events, and the overall end-result, are examined here with an illustrative example.

The “base” allele frequencies of the example are those of the potential gamodeme: the frequency of A is pg = 0.75, while the frequency of a is qg = 0.25. [White label “1” in the diagram.] Five example actual gamodemes are binomially sampled out of this base (s = the number of samples = 5), and each sample is designated with an “index” k: with k = 1 …. s sequentially. (These are the sampling “packets” referred to in the previous paragraph.) The number of gametes involved in fertilization varies from sample to sample, and is given as 2Nk [at white label “2” in the diagram]. The total () number of gametes sampled overall is 52 [white label “3” in the diagram]. Because each sample has its own size, weights are needed to obtain averages (and other statistics) when obtaining the overall results. These are k = 2 N k / ( k s 2 N k ) {textstyle omega _{k}=2N_{k}/(sum _{k}^{s}2N_{k})} , and are given at white label “4” in the diagram.

Following completion of these five binomial sampling events, the resultant actual gamodemes each contained different allele frequencies(pk and qk). [These are given at white label “5” in the diagram.] This outcome is actually the genetic drift itself. Notice that two samples (k = 1 and 5) happen to have the same frequencies as the base (potential) gamodeme. Another (k = 3) happens to have the p and q “reversed”. Sample (k = 2) happens to be an “extreme” case, with pk = 0.9 and qk = 0.1; while the remaining sample (k = 4) is “middle of the range” in its allele frequencies. All of these results have arisen only by “chance”, through binomial sampling. Having occurred, however, they set in place all the downstream properties of the progenies.

Because sampling involves chance, the probabilities ( k ) of obtaining each of these samples become of interest. These binomial probabilities depend on the starting frequencies (pg and qg) and the sample size (2Nk). They are tedious to obtain,[13]:382395[30]:55 but are of considerable interest. [See white label “6” in the diagram.] The two samples (k = 1, 5), with the allele frequencies the same as in the potential gamodeme, had higher “chances” of occurring than the other samples. Their binomial probabilities did differ, however, because of their different sample sizes (2Nk). The “reversal” sample (k = 3) had a very low Probability of occurring, confirming perhaps what might be expected. The “extreme” allele frequency gamodeme (k = 2) was not “rare”, however; and the “middle of the range” sample (k=4) was rare. These same Probabilities apply also to the progeny of these fertilizations.

Here, some summarizing can begin. The overall allele frequencies in the progenies bulk are supplied by weighted averages of the appropriate frequencies of the individual samples. That is: p = k s k p k {textstyle p_{centerdot }=sum _{k}^{s}omega _{k} p_{k}} and q = k s k q k {textstyle q_{centerdot }=sum _{k}^{s}omega _{k} q_{k}} . (Notice that k is replaced by for the overall result – a common practice.)[9] The results for the example are p = 0.631 and q = 0.369 [black label “5” in the diagram]. These values are quite different to the starting ones (pg and qg) [white label “1”]. The sample allele frequencies also have variance as well as an average. This has been obtained using the sum of squares (SS) method [31] [See to the right of black label “5” in the diagram]. [Further discussion on this variance occurs in the section below on Extensive genetic drift.]

The genotype frequencies of the five sample progenies are obtained from the usual quadratic expansion of their respective allele frequencies (random fertilization). The results are given at the diagram’s white label “7” for the homozygotes, and at white label “8” for the heterozygotes. Re-arrangement in this manner prepares the way for monitoring inbreeding levels. This can be done either by examining the level of total homozygosis [(p2k + q2k) = (1 – 2pkqk)] , or by examining the level of heterozygosis (2pkqk), as they are complementary.[32] Notice that samples k= 1, 3, 5 all had the same level of heterozygosis, despite one being the “mirror image” of the others with respect to allele frequencies. The “extreme” allele-frequency case (k= 2) had the most homozygosis (least heterozygosis) of any sample. The “middle of the range” case (k= 4) had the least homozygosity (most heterozygosity): they were each equal at 0.50, in fact.

The overall summary can continue by obtaining the weighted average of the respective genotype frequencies for the progeny bulk. Thus, for AA, it is p 2 = k s k p k 2 {textstyle p_{centerdot }^{2}=sum _{k}^{s}omega _{k} p_{k}^{2}} , for Aa , it is 2 p q = k s k 2 p k q k {textstyle 2p_{centerdot }q_{centerdot }=sum _{k}^{s}omega _{k} 2p_{k}q_{k}} and for aa, it is q 2 = k s k q k 2 {textstyle q_{centerdot }^{2}=sum _{k}^{s}omega _{k} q_{k}^{2}} . The example results are given at black label “7” for the homozygotes, and at black label “8” for the heterozygote. Note that the heterozygosity mean is 0.3588, which the next section uses to examine inbreeding resulting from this genetic drift.

The next focus of interest is the dispersion itself, which refers to the “spreading apart” of the progenies’ population means. These are obtained as G k = a ( p k q k ) + 2 p k q k d {textstyle G_{k}=a(p_{k}-q_{k})+2p_{k}q_{k}d} [see section on the Population mean], for each sample progeny in turn, using the example gene effects given at white label “9” in the diagram. Then, each P k = G k + m p {textstyle P_{k}=G_{k}+mp} is obtained also [at white label “10” in the diagram]. Notice that the “best” line (k = 2) had the highest allele frequency for the “more” allele (A) (it also had the highest level of homozygosity). The worst progeny (k = 3) had the highest frequency for the “less” allele (a), which accounted for its poor performance. This “poor” line was less homozygous than the “best” line; and it shared the same level of homozygosity, in fact, as the two second-best lines (k = 1, 5). The progeny line with both the “more” and the “less” alleles present in equal frequency (k = 4) had a mean below the overall average (see next paragraph), and had the lowest level of homozygosity. These results reveal the fact that the alleles most prevalent in the “gene-pool” (also called the “germplasm”) determine performance, not the level of homozygosity per se. Binomial sampling alone effects this dispersion.

The overall summary can now be concluded by obtaining G = k s k G k {textstyle G_{centerdot }=sum _{k}^{s}omega _{k} G_{k}} and P = k s k P k {textstyle P_{centerdot }=sum _{k}^{s}omega _{k} P_{k}} . The example result for P is 36.94 (black label “10” in the diagram). This later is used to quantify inbreeding depression overall, from the gamete sampling. [See the next section.] However, recall that some “non-depressed” progeny means have been identified already (k = 1, 2, 5). This is an enigma of inbreeding – while there may be “depression” overall, there are usually superior lines among the gamodeme samplings.

Included in the overall summary were the averaqe allele frequencies in the mixture of progeny lines (p and q). These can now be used to construct a hypothetical panmictic equivalent.[13]:382395[14]:4963[29]:35 This can be regarded as a “reference” to assess the changes wrought by the gamete sampling. The example appends such a panmictic to the right of the Diagram. The frequency of AA is therefore (p)2 = 0.3979. This is less than that found in the dispersed bulk (0.4513 at black label “7”). Similarly, for aa, (q)2 = 0.1303 – again less than the equivalent in the progenies bulk (0.1898). Clearly, genetic drift has increased the overall level of homozygosis by the amount (0.6411 – 0.5342) = 0.1069. In a complementary approach, the heterozygosity could be used instead. The panmictic equivalent for Aa is 2 p q = 0.4658, which is higher than that in the sampled bulk (0.3588) [black label “8”]. The sampling has caused the heterozygosity to decrease by 0.1070, which differs trivially from the earlier estimate because of rounding errors.

The inbreeding coefficient (f) was introduced in the early section on Self Fertilization. Here, a formal definition of it is considered: f is the probability that two “same” alleles (that is A and A, or a and a), which fertilize together are of common ancestral origin – or (more formally) f is the probability that two homologous alleles are autozygous.[14][27] Consider any random gamete in the potential gamodeme that has its syngamy partner restricted by binomial sampling. The probability that that second gamete is homologous autozygous to the first is 1/(2N), the reciprocal of the gamodeme size. For the five example progenies, these quantities are 0.1, 0.0833, 0.1, 0.0833 and 0.125 respectively, and their weighted average is 0.0961. This is the inbreeding coefficient of the example progenies bulk, provided it is unbiased with respect to the full binomial distribution. An example based upon s = 5 is likely to be biased, however, when compared to an appropriate entire binomial distribution based upon the sample number (s) approaching infinity (s ). Another derived definition of f for the full Distribution is that f also equals the rise in homozygosity, which equals the fall in heterozygosity.[33] For the example, these frequency changes are 0.1069 and 0.1070, respectively. This result is different to the above, indicating that bias with respect to the full underlying distribution is present in the example. For the example itself, these latter values are the better ones to use, namely f = 0.10695.

The population mean of the equivalent panmictic is found as [a (p-q) + 2 pq d] + mp. Using the example gene effects (white label “9” in the diagram), this mean is P = {textstyle P_{centerdot }=} 37.87. The equivalent mean in the dispersed bulk is 36.94 (black label “10”), which is depressed by the amount 0.93. This is the inbreeding depression from this Genetic Drift. However, as noted previously, three progenies were not depressed (k = 1, 2, 5), and had means even greater than that of the panmictic equivalent. These are the lines a plant breeder looks for in a line selection programme.[34]

If the number of binomial samples is large (s ), then p pg and q qg. It might be queried whether panmixia would effectively re-appear under these circumstances. However, the sampling of allele frequencies has still occurred, with the result that 2p, q 0.[35] In fact, as s , the p , q 2 p g q g 2 N {textstyle sigma _{p, q}^{2}to {tfrac {p_{g}q_{g}}{2N}}} , which is the variance of the whole binomial distribution.[13]:382395[14]:4963 Furthermore, the “Wahlund equations” show that the progeny-bulk homozygote frequencies can be obtained as the sums of their respective average values (p2 or q2) plus 2p, q.[13]:382395 Likewise, the bulk heterozygote frequency is (2 p q) minus twice the 2p, q. The variance arising from the binomial sampling is conspicuously present. Thus, even when s , the progeny-bulk genotype frequencies still reveal increased homozygosis, and decreased heterozygosis, there is still dispersion of progeny means, and still inbreeding and inbreeding depression. That is, panmixia is not re-attained once lost because of genetic drift (binomial sampling). However, a new potential panmixia can be initiated via an allogamous F2 following hybridization.[36]

Previous discussion on genetic drift examined just one cycle (generation) of the process. When the sampling continues over successive generations, conspicuous changes occur in 2p, q and f. Furthermore, another “index” is needed to keep track of “time”: t = 1 …. y where y = the number of “years” (generations) considered. The methodology often is to add the current binomial increment ( = “de novo”) to what has occurred previously.[13] The entire Binomial Distribution is examined here. [There is no further benefit to be had from an abbreviated example.]

Earlier this variance ( 2p,q[35]) was seen to be:-

p , q 2 = p g q g / 2 N = p g q g ( 1 2 N ) = p g q g f = p g q g f when used in recursive equations {displaystyle {begin{aligned}sigma _{p,q}^{2}&=p_{g}q_{g} / 2N\&=p_{g}q_{g}left({frac {1}{2N}}right)\&=p_{g}q_{g} f\&=p_{g}q_{g} Delta f scriptstyle {text{when used in recursive equations}}end{aligned}}}

With the extension over time, this is also the result of the first cycle, and so is 1 2 {textstyle sigma _{1}^{2}} (for brevity). At cycle 2, this variance is generated yet again – this time becoming the de novo variance ( 2 {textstyle Delta sigma ^{2}} ) – and accumulates to what was present already – the “carry-over” variance. The second cycle variance ( 2 2 {textstyle sigma _{2}^{2}} ) is the weighted sum of these two components, the weights being 1 {textstyle 1} for the de novo and ( 1 1 2 N ) {textstyle left(1-{tfrac {1}{2N}}right)} = ( 1 f ) {textstyle left(1-Delta fright)} for the”carry-over”.


2 2 = ( 1 ) 2 + ( 1 f ) 1 2 {displaystyle sigma _{2}^{2}=left(1right) Delta sigma ^{2}+left(1-Delta fright)sigma _{1}^{2}}

( 1)

The extension to generalize to any time t , after considerable simplification, becomes:[13]:328-

t 2 = p g q g [ 1 ( 1 f ) t ] {displaystyle sigma _{t}^{2}=p_{g}q_{g}left[1-left(1-Delta fright)^{t}right]}

( 2)

Because it was this variation in allele frequencies that caused the “spreading apart” of the progenies’ means (dispersion), the change in 2t over the generations indicates the change in the level of the dispersion.

The method for examining the inbreeding coefficient is similar to that used for 2p,q. The same weights as before are used respectively for de novo f ( f ) [recall this is 1/(2N) ] and carry-over f. Therefore, f 2 = ( 1 ) f + ( 1 f ) f 1 {textstyle f_{2}=left(1right)Delta f+left(1-Delta fright)f_{1}} , which is similar to Equation (1) in the previous sub-section.

In general, after rearrangement,[13]

f t = f + ( 1 f ) f t 1 = f ( 1 f t 1 ) + f t 1 {displaystyle {begin{aligned}f_{t}&=Delta f+left(1-Delta fright)f_{t-1}\&=Delta fleft(1-f_{t-1}right)+f_{t-1}end{aligned}}}

Still further rearrangements of this general equation reveal some interesting relationships.

(A) After some simplification,[13] ( f t f t 1 ) = f ( 1 f t 1 ) = f t {textstyle left(f_{t}-f_{t-1}right)=Delta fleft(1-f_{t-1}right)=delta f_{t}} . The left-hand side is the difference between the current and previous levels of inbreeding: the change in inbreeding (ft). Notice, that this change in inbreeding (ft) is equal to the de novo inbreeding (f) only for the first cycle – when ft-1 is zero.

(B) An item of note is the (1-ft-1), which is an “index of non-inbreeding”. It is known as the panmictic index.[13][14] P t 1 = ( 1 f t 1 ) {textstyle P_{t-1}=left(1-f_{t-1}right)} .

(C) Further useful relationships emerge involving the panmictic index.[13][14]

f = f t P t 1 = 1 P t P t 1 {displaystyle {begin{aligned}Delta f&={frac {delta f_{t}}{P_{t-1}}}\&=1-{frac {P_{t}}{P_{t-1}}}end{aligned}}}

f t = 1 ( 1 1 f ) t ( 1 f 0 ) {displaystyle {begin{aligned}f_{t}&=1-left(1-1Delta fright)^{t}left(1-f_{0}right)end{aligned}}}

It is easy to overlook that random fertilization includes self-fertilization. Sewall Wright showed that a proportion 1/N of random fertilizations is actually self fertilization ( ) {displaystyle left(bigotimes right)} , with the remainder (N-1)/N being cross fertilization ( X ) {displaystyle left({mathsf {X}}right)} . Following path analysis and simplification, the new view random fertilization inbreeding was found to be: f t = f ( 1 + f t 1 ) + N 1 N f t 1 {textstyle f_{t}=Delta fleft(1+f_{t-1}right)+{tfrac {N-1}{N}}f_{t-1}} .[27][37] Upon further rearrangement, the earlier results from the binomial sampling were confirmed, along with some new arrangements. Two of these were potentially very useful, namely: (A) f t = f [ 1 + f t 1 ( 2 N 1 ) ] {textstyle f_{t}=Delta fleft[1+f_{t-1}left(2N-1right)right]} ; and (B) f t = f ( 1 f t 1 ) + f t 1 {textstyle f_{t}=Delta fleft(1-f_{t-1}right)+f_{t-1}} .

The recognition that selfing may intrinsically be a part of random fertilization leads to some issues about the use of the previous random fertilization ‘inbreeding coefficient’. Clearly, then, it is inappropriate for any species incapable of self fertilization, which includes plants with self-incompatibility mechanisms, dioecious plants, and bisexual animals. The equation of Wright was modified later to provide a version of random fertilization that involved only cross fertilization with no self fertilization. The proportion 1/N formerly due to selfing now defined the carry-over gene-drift inbreeding arising from the previous cycle. The new version is:[13]:166

f X t = f t 1 + f ( 1 + f t 2 2 f t 1 ) {displaystyle f_{{mathsf {X}}_{t}}=f_{t-1}+Delta fleft(1+f_{t-2}-2f_{t-1}right)}

The graphs to the right depict the differences between standard random fertilization RF, and random fertilization adjusted for “cross fertilization alone” CF. As can be seen, the issue is non-trivial for small gamodeme sample sizes.

It now is necessary to note that not only is “panmixia” not a synonym for “random fertilization”, but also that “random fertilization” is not a synonym for “cross fertilization”.

In the sub-section on the “The sample gamodemes – Genetic drift”, a series of gamete samplings was followed, an outcome of which was an increase in homozygosity at the expense of heterozygosity. From this viewpoint, the rise in homozygosity was due to the gamete samplings. Levels of homozygosity can be viewed also according to whether homozygotes arose allozygously or autozygously. Recall that autozygous alleles have the same allelic origin, the likelihood (frequency) of which is the inbreeding coefficient (f) by definition. The proportion arising allozygously is therefore (1-f). For the A-bearing gametes, which are present with a general frequency of p, the overall frequency of those that are autozygous is therefore (f p). Similarly, for a-bearing gametes, the autozygous frequency is (f q).[38] These two viewpoints regarding genotype frequencies must be connected to establish consistency.

Following firstly the auto/allo viewpoint, consider the allozygous component. This occurs with the frequency of (1-f), and the alleles unite according to the random fertilization quadratic expansion. Thus:

( 1 f ) [ p 0 + q 0 ] 2 = ( 1 f ) [ p 0 2 + q 0 2 ] + ( 1 f ) [ 2 p 0 q 0 ] {displaystyle left(1-fright)left[p_{0}+q_{0}right]^{2}=left(1-fright)left[p_{0}^{2}+q_{0}^{2}right]+left(1-fright)left[2p_{0}q_{0}right]}

Secondly, the sampling viewpoint is re-examined. Previously, it was noted that the decline in heterozygotes was f ( 2 p 0 q 0 ) {textstyle fleft(2p_{0}q_{0}right)} . This decline is distributed equally towards each homozygote; and is added to their basic random fertilization expectations. Therefore, the genotype frequencies are: ( p 0 2 + f p 0 q 0 ) {textstyle left(p_{0}^{2}+fp_{0}q_{0}right)} for the “AA” homozygote; ( q 0 2 + f p 0 q 0 ) {textstyle left(q_{0}^{2}+fp_{0}q_{0}right)} for the “aa” homozygote; and 2 p 0 q 0 f ( 2 p 0 q 0 ) {textstyle 2p_{0}q_{0}-fleft(2p_{0}q_{0}right)} for the heterozygote.

Thirdly, the consistency between the two previous viewpoints needs establishing. It is apparent at once [from the corresponding equations above] that the heterozygote frequency is the same in both viewpoints. However, such a straightforward result is not immediately apparent for the homozygotes. Begin by considering the AA homozygote’s final equation in the auto/allo paragraph above:- [ ( 1 f ) p 0 2 + f p 0 ] {textstyle left[left(1-fright)p_{0}^{2}+fp_{0}right]} . Expand the brackets, and follow by re-gathering [within the resultant] the two new terms with the common-factor f in them. The result is: p 0 2 f ( p 0 2 p 0 ) {textstyle p_{0}^{2}-fleft(p_{0}^{2}-p_{0}right)} . Next, for the parenthesized ” p20 “, a (1-q) is substituted for a p, the result becoming p 0 2 f [ p 0 ( 1 q 0 ) p 0 ] {textstyle p_{0}^{2}-fleft[p_{0}left(1-q_{0}right)-p_{0}right]} . Following that substitution, it is a straightforward matter of multiplying-out, simplifying and watching signs. The end result is p 0 2 + f p 0 q 0 {textstyle p_{0}^{2}+fp_{0}q_{0}} , which is exactly the result for AA in the sampling paragraph. The two viewpoints are therefore consistent for the AA homozygote. In a like manner, the consistency of the aa viewpoints can also be shown. The two viewpoints are consistent for all classes of genotypes.

In previous sections, dispersive random fertilization (genetic drift) has been considered comprehensively, and self-fertilization and hybridizing have been examined to varying degrees. The diagram to the left depicts the first two of these, along with another “spatially based” pattern: islands. This is a pattern of random fertilization featuring dispersed gamodemes, with the addition of “overlaps” in which non-dispersive random fertilization occurs. With the islands pattern, individual gamodeme sizes (2N) are observable, and overlaps (m) are minimal. This is one of Sewall Wright’s array of possibilities.[37] In addition to “spatially” based patterns of fertilization, there are others based on either “phenotypic” or “relationship” criteria. The phenotypic bases include assortative fertilization (between similar phenotypes) and disassortative fertilization (between opposite phenotypes). The relationship patterns include sib crossing, cousin crossing and backcrossingand are considered in a separate section. Self fertilization may be considered both from a spatial or relationship point of view.

The breeding population consists of s small dispersed random fertilization gamodemes of sample size 2 N k {textstyle 2N_{k}} ( k = 1 … s ) with ” overlaps ” of proportion m k {textstyle m_{k}} in which non-dispersive random fertilization occurs. The dispersive proportion is thus ( 1 m k ) {textstyle left(1-m_{k}right)} . The bulk population consists of weighted averages of sample sizes, allele and genotype frequencies and progeny means, as was done for genetic drift in an earlier section. However, each gamete sample size is reduced to allow for the overlaps, thus finding a 2 N k {textstyle 2N_{k}} effective for ( 1 m k ) {textstyle left(1-m_{k}right)} .

For brevity, the argument is followed further with the subscripts omitted. Recall that 1 2 N {textstyle {tfrac {1}{2N}}} is f {textstyle Delta f} in general. [Here, and following, the 2N refers to the previously defined sample size, not to any “islands adjusted” version.]

After simplification,[37]

i s l a n d s f = ( 1 m ) 2 2 N m 2 ( 2 N 1 ) {displaystyle ^{mathsf {islands}}Delta f={frac {left(1-mright)^{2}}{2N-m^{2}left(2N-1right)}}}

This f is also substituted into the previous inbreeding coefficient to obtain [37]

i s l a n d s f t = i s l a n d s f t + ( 1 i s l a n d s f t ) i s l a n d s f t 1 {displaystyle {^{mathsf {islands}}f_{t}}= {^{mathsf {islands}}Delta f_{t}}+left(1- {^{mathsf {islands}}Delta f_{t}}right) {^{mathsf {islands}}f_{t-1}}}

The effective overlap proportion can be obtained also,[37] as

m t = 1 [ 2 N i s l a n d s f t ( 2 N 1 ) i s l a n d s f t + 1 ] 1 2 {displaystyle m_{t}=1-left[{frac {2N {^{mathsf {islands}}Delta f_{t}}}{left(2N-1right) {^{mathsf {islands}}Delta f_{t}+1}}}right]^{tfrac {1}{2}}}

The graphs to the right show the inbreeding for a gamodeme size of 2N = 50 for ordinary dispersed random fertilization (RF) (m=0), and for four overlap levels ( m = 0.0625, 0.125, 0.25, 0.5 ) of islands random fertilization. There has indeed been reduction in the inbreeding resulting from the non-dispersed random fertilization in the overlaps. It is particularly notable as m 0.50. Sewall Wright suggested that this value should be the limit for the use of this approach.[37]

The gene-model examines the heredity pathway from the point of view of “inputs” (alleles/gametes) and “outputs” (genotypes/zygotes), with fertilization being the “process” converting one to the other. An alternative viewpoint concentrates on the “process” itself, and considers the zygote genotypes as arising from allele shuffling. In particular, it regards the results as if one allele had “substituted” for the other during the shuffle, together with a residual that deviates from this view. This formed an integral part of Fisher’s method,[8] in addition to his use of frequencies and effects to generate his genetical statistics.[14] A discursive derivation of the allele substitution alternative follows.[14]:113

Suppose that the usual random fertilization of gametes in a “base” gamodeme – consisting of p gametes (A) and q gametes (a) – is replaced by fertilization with a “flood” of gametes all containing a single allele (A or a, but not both). The zygotic results can be interpreted in terms of the “flood” allele having “substituted for” the alternative allele in the underlying “base” gamodeme. The diagram assists in following this viewpoint: the upper part pictures an A substitution, while the lower part shows an a substitution. (The diagram’s “RF allele” is the allele in the “base” gamodeme.)

Consider the upper part firstly. Because base A is present with a frequency of p, the substitute A fertilizes it with a frequency of p resulting in a zygote AA with an allele effect of a. Its contribution to the outcome, therefore, is the product ( p a ) {textstyle left(p aright)} . Similarly, when the substitute fertilizes base a (resulting in Aa with a frequency of q and heterozygote effect of d), the contribution is ( q d ) {textstyle left(q dright)} . The overall result of substitution by A is, therefore, ( p a + q d ) {textstyle left(p a+q dright)} . This is now oriented towards the population mean [see earlier section] by expressing it as a deviate from that mean: ( p a + q d ) G {textstyle left(p a+q dright)-G}

After some algebraic simplification, this becomes

A = q [ a + ( q p ) d ] {displaystyle beta _{A}=q left[a+left(q-pright)dright]}

A parallel reasoning can be applied to the lower part of the diagram, taking care with the differences in frequencies and gene effects. The result is the substitution effect of a, which is

a = p [ a + ( q p ) d ] {displaystyle beta _{a}=- pleft[a+left(q-pright)dright]}

= a + ( q p ) d {displaystyle beta =a+left(q-pright)d}

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Quantitative genetics – Wikipedia

Recommendation and review posted by Bethany Smith

DIM for Hormone Balance –

DIM (diindolylmethane), is a food-based compound found in cruciferous vegetables like broccoli, cabbage, cauliflower and Brussels sprouts.Studies have shown that it has the ability to reduce the risk of certain cancers, especiallythose influenced by excessive estrogen levels, such as breast, uterine and prostate. DIM can also stimulatefat breakdown and encourage an increase in muscle mass. I can attest, through my own personal experience supplementing with DIM as well as that of quite a few clients (both male and female), that DIM effectively modulates estrogen metabolism helping to do away with uncomfortable symptoms of PMS, perimenopause and prostate issues.

The following excerpt comes from Dr. Scott Rollins, MD, founder and Medical Director at the Integrative Medicine Center of Western Colorado ( Thisis a very well-written and comprehensive account of the effects of DIM and how to best use this supplement to make the most out of its incredible benefits:

Lower your risk of cancer, help lose weight and build muscle all remarkable benefits of a simple food supplement called DIM. For men or women, DIM is something to consider as part of an overall supplement program.

DIM, or diindolylmethane, is a plant based compound found in cruciferous vegetables, such as brussel sprouts,cabbage, broccoli and cauliflower. DIM has been shown in studies to reduce the risk of certain cancers, especiallythose driven by abnormally high estrogen levels, such as breast, uterus and prostate cancer. DIM can also stimulate the breakdown of fat while encouraging muscle development.

Estrogen hormones are naturally found in men and women and have many benefits such as preserving artery healthand brain function while fighting oxidative free radical damage. Higher estrogen levels found in women cause thefemale body shape with breast and hip development. Many women are estrogen dominant however, meaning theyhave too much estrogen accumulating in the body for the complementary progesterone to balance.

Natural estrogen dominance occurs as women near menopause, starting even ten years prior to menopause, where theyoften dont make as much progesterone to balance their estrogen. Symptoms such breast pain, water retention, heavypainful menstrual cycles, or irritable anxious moods are typical bothersome symptoms. Estrogens over-stimulation ofbreasts and uterus tissue can lead to breast cysts or adenomas and uterine growths both unpleasant and potentiallydangerous physical outcomes are too often accompanied by worrisome mammograms and hysterectomies.

Some women have estrogen dominance throughout their life for various reasons, such as low thyroid, high cortisol,exposure to environmental estrogen-like chemicals, or impaired detoxification pathways for estrogen.

Men often suffer from estrogen overload as well. With normal aging our testosterone levels drop as the conversion toestrogen increases, leading to a falling ratio of testosterone to estrogen. Higher estrogen levels in men lead to weightgain, loss of muscle mass, feminization of the body, further decreases in already falling testosterone levels, andincrease the risk of diseases such as heart disease and prostate cancer. The enzyme that normally converts testosteroneto estrogen is most abundant in fat, so as men put on weight the cycle of falling testosterone and rising estrogen simply picks up steam!

There are two main pathways in the liver for our estrogen to be normally metabolized and excreted. One pathwayleads to very good metabolites called 2-hydroxy estrogens. The other pathway leads to bad metabolites called 4 or 16-hydroxy estrogens. DIM stimulates the favorable 2-hydroxy pathway for estrogen metabolism and this is how DIMworks to improve our health.DIM is not a hormone, nor is it a hormone replacement. It is a plant compound that will improve our hormonebalance. By improving the metabolism of our natural estrogens DIM will help lower high levels of estrogen in thebody. This alone can help remedy estrogen dominant conditions and restore a healthy estrogen/testosterone ratio inmen and women.The favorable 2-hydroxy metabolites promoted by DIM are potent anti-oxidants and help prevent muscle breakdownafter exercise, as evidenced by female athletes having less muscle tissue breakdown after intense exercise than men.By reducing the estrogen dominance and also reducing the accumulation of cancer-promoting 4/16-hydroxymetabolites DIM can help lower the risk of cancer.The 2-hydroxy metabolites help increase the active testosterone levels in men and women by displacing inactiveprotein-bound testosterone to its active free portion. This leads to significant improvements in the ability to buildmuscle and enjoy the benefits of testosterone including better mood, increased stamina, endurance, sex drive anderectile function.The accumulation of fat around the belly, hips and buttocks is partly due to excess estrogen levels combined withfalling testosterone levels. DIM will help lower excess estrogen and promote the fat-burning 2-hydroxy metabolites.This can help you achieve a leaner body with less body fat.

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DIM for Hormone Balance –

Recommendation and review posted by Bethany Smith

Hormonal Imbalance Anxiety a Precursor to Other Health …

Leslie Carol Botha: I originally posted this article in 2009. Thought it was well-written then and still think so. However, in the past two weeks readers of my blog have dug back into the HHH archives and have commented on their own hormonal anxiety so I decided to repost it in June 2012. Now 288 posts later it appears that hormone imbalance has become a silent epidemic affecting women of all ages.

Hormone imbalance -in the form of estrogen dominance which can cause hormone-related anxiety, insomnia, weight gain, emotional rage, phobias, and diabetes is due to the plastics in our environment. throw out all of your plastic water bottles they contain high amounts of estrogen mimickers, AND DO NOT MICROWAVE IN PLASTIC. Estrogen mimickers are found in food, household chemicals and our water supply from the high amounts of synthetic estrogen being excreted into the water streams from synthetic birth control and HRT. I kid you not. There have been plenty of articles about fishing changing their sex because of excreted hormones.

Lastly we are now 3 to 4 generations into synthetic hormone suppression, i.e., birth control (pills, IUDs implants, injections, rings, and patches). All of the estrogen is being built up in the body and passed in-utero to the fetus. So you will note many young women who have posted comments about hormone imbalance too. This is sad. We are upsetting the hormone chemical balance in the body. Women are suffering. And if we do not correct the imbalance it will only get worse. Such is the nature of not taking care of our health.

I believe that most women experience hormonal anxiety in one form or another. Unfortunately, the medical and psychiatric professions are quick to diagnosis and label with syndromes and then proceed to treat with drugs.

Now we know that source of this misdiagnosis is, in most cases hormone imbalance it can be corrected through nutritional supplementation, and hormone balancing. Most women are estrogen dependent. I have been recommending Progessence Plus that contains a wild yam extract infused with essential oils that repair the DNA and clear off the receptor sites on our cells so that the natural progesterone can be absorbed into the cell and not remain in fatty tissue of the body. By Shelly Mcrae, eHow Editor


Everyone experiences anxiety at one point or another, such as before an important test in school, an important presentation at work, during the holidays or when experiencing a crisis of any kind. Anxiety in these instances help you stay alert, focus on tasks at hand or make quick decisions.

But when anxiety turns into an ongoing sense of apprehension, or begins to manifest as debilitating fear, it may be due to personality disorder or a hormonal imbalance. Its important to determine the cause of your anxiety and determine how to treat it.

When these fears and paranoid thoughts manifest themselves and then fade within 30 minutes or so, it is referred to as a panic attack. You may be so overwhelmed by the mental and physical symptoms that you feel unable to go on and instead try to escape, literally going home or someplace you feel safe. In such cases, you may have a personality disorder.

In cases in which hormonal imbalances are the root cause, as opposed to a personality disorder, the anxiety may not be so severe as to be labeled a panic attack. Rather, it more closely resembles mood swings or depression. But rather than feeling sad or irritable, you feel apprehension and uneasiness.

Anxiety induced by hormonal imbalances, such as estrogen dominance in which the level of the hormone progesterone is very low, differs from those panic attacks associated with personality disorders such as bipolar or obsessive-compulsive disorders. But there are also similarities. Determining the root cause of the anxiety can determine which treatment is appropriate.

The inability to control the onslaught of negative thoughts is symptomatic in both panic attacks and anxiety. Anxiety, though, may be more consistent and you may display fewer physical symptoms. You may feel that it is all in your head.

The sense of anxiety may not be as exaggerated as for those suffering from personality disorders. Instead, you may feel uneasy in social situations, be reluctant to make decisions or continually worry over problems that are relatively minor.

But your anxiety may not be limited to the more subtle form. In cases of severe hormonal imbalance, you may suffer full-blown panic attacks in which fear, though irrational, overwhelms your reasoning. You may be unable to explain why you are reacting to a simple incident as if it were a life crisis.

One of the characteristics of both panic attack and anxiety due to hormonal imbalances is the levels of cortisol in the system. Cortisol is the chemical released by the adrenals that activates the fight or flight response.The hypothalamic-pituitary-adrenal (HPA) axis is the hormonal system that controls your mood. If you suffer from a hormonal imbalance, this system may go into overdrive. The result is that your body and mind will believe a threatening situation exists, which in turn results in feelings of apprehension, fear and dread.

Treatments for hormonal imbalance range from basic lifestyle changes to replacement hormone therapy. Bioidentical hormones, which are naturally occurring hormones found in plants and synthesized for human consumption, are a common treatment when anxiety is one of the symptoms of hormonal imbalance.

In the case of severe panic attacks, such medications as benzodiazepines and antidepressants may be necessary to control the attacks. These are common treatments for personality disorders. (I DO NOT AGREE WITH THIS STATEMENT. LB.)

Left untreated, mild anxiety can worsen, resulting in debilitating behavior patterns due to unwarranted fear. Whether the underlying cause is personality disorder or hormonal imbalance, effective treatment is available.

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Hormonal Imbalance Anxiety a Precursor to Other Health …

Recommendation and review posted by Bethany Smith