"Low T" redirects here. It is not to be confused with LOWT or T Low.

Endocrine disease

Hypogonadism means diminished functional activity of the gonadsthe testes or the ovariesthat may result in diminished production of sex hormones.

Low androgen (e.g., testosterone) levels are referred to as hypoandrogenism and low estrogen (e.g., estradiol) as hypoestrogenism. These are responsible for the observed signs and symptoms. Hypogonadism can decrease other hormones secreted by the gonads including progesterone, DHEA, anti-Mllerian hormone, activin, and inhibin. Sperm development (spermatogenesis) and release of the egg from the ovaries (ovulation) may be impaired by hypogonadism, which, depending on the degree of severity, may result in partial or complete difficulty or inability to have children.

In January 2020, the American College of Physicians issued clinical guidelines for testosterone treatment in adult men with age-related low levels of testosterone. The guidelines are supported by the American Academy of Family Physicians. The guidelines include patient discussions regarding testosterone treatment for sexual dysfunction; annual patient evaluation regarding possible notable improvement and, if none, to discontinue testosterone treatment; physicians should consider intramuscular treatments, rather than transdermal treatments, due to costs and since the effectiveness and harm of either method is similar; and, testosterone treatment for reasons other than possible improvement of sexual dysfunction may not be recommended.[1][2]

Deficiency of sex hormones can result in defective primary or secondary sexual development, or withdrawal effects (e.g., premature menopause) in adults. Defective egg or sperm development results in infertility. The term hypogonadism usually means permanent rather than transient or reversible defects, and usually implies deficiency of reproductive hormones, with or without fertility defects. The term is less commonly used for infertility without hormone deficiency. There are many possible types of hypogonadism and several ways to categorize them. Hypogonadism is also categorized by endocrinologists by the level of the reproductive system that is defective. Physicians measure gonadotropins (LH and FSH) to distinguish primary from secondary hypogonadism. In primary hypogonadism the LH and/or FSH are usually elevated, meaning the problem is in the testicles, whereas in secondary hypogonadism, both are normal or low, suggesting the problem is in the brain.

Hypogonadism can involve just hormone production or just fertility, but most commonly involves both.

Women with hypogonadism do not begin menstruating and it may affect their height and breast development. Onset in women after puberty causes cessation of menstruation, lowered libido, loss of body hair, and hot flashes. In men it causes impaired muscle and body hair development, gynecomastia, decreased height, erectile dysfunction, and sexual difficulties. If hypogonadism is caused by a disorder of the central nervous system (e.g., a brain tumor), then this is known as central hypogonadism. Signs and symptoms of central hypogonadism may involve headaches, impaired vision, double vision, milky discharge from the breast, and symptoms caused by other hormone problems.[5]

The symptoms of hypogonadotrophic hypogonadism, a subtype of hypogonadism, include late, incomplete or lack of development at puberty, and sometimes short stature or the inability to smell; in females, a lack of breasts and menstrual periods, and in males a lack of sexual development, e.g., facial hair, penis and testes enlargement, deepening voice.

Low testosterone can be identified through a simple blood test performed by a laboratory, ordered by a health care provider. Blood for the test must be taken in the morning hours, when levels are highest, as levels can drop by as much as 13% during the day and all normal reference ranges are based on morning levels.[6] However, low testosterone in the absence of any symptoms does not clearly need to be treated.

Normal total testosterone levels depend on the man's age but generally range from 240950ng/dL (nanograms per deciliter) or 8.3-32.9 nmol/L (nanomoles per liter).[7] According to American Urological Association, the diagnosis of low testosterone can be supported when the total testosterone level is below 300ng/dl.[8] Some men with normal total testosterone have low free or bioavailable testosterone levels which could still account for their symptoms. Men with low serum testosterone levels should have other hormones checked, particularly luteinizing hormone to help determine why their testosterone levels are low and help choose the most appropriate treatment (most notably, testosterone is usually not appropriate for secondary or tertiary forms of male hypogonadism, in which the LH levels are usually reduced).

Treatment is often prescribed for total testosterone levels below 230ng/dL with symptoms.[9] If the serum total testosterone level is between 230 and 350ng/dL, free or bioavailable testosterone should be checked as they are frequently low when the total is marginal.

The standard range given is based on widely varying ages and, given that testosterone levels naturally decrease as humans age, age-group specific averages should be taken into consideration when discussing treatment between doctor and patient.[10] In men, testosterone falls approximately 1 to 3 percent each year.[11]

A position statement by the Endocrine Society expressed dissatisfaction with most assays for total, free, and bioavailable testosterone.[12] In particular, research has questioned the validity of commonly administered assays of free testosterone by radioimmunoassay.[12] The free androgen index, essentially a calculation based on total testosterone and sex hormone-binding globulin levels, has been found to be the worst predictor of free testosterone levels and should not be used.[13] Measurement by equilibrium dialysis or mass spectroscopy is generally required for accurate results, particularly for free testosterone which is normally present in very small concentrations.

Testing serum LH and FSH levels are often used to assess hypogonadism in women, particularly when menopause is believed to be happening. These levels change during a woman's normal menstrual cycle, so the history of having ceased menstruation coupled with high levels aids the diagnosis of being menopausal. Commonly, the post-menopausal woman is not called hypogonadal if she is of typical menopausal age. Contrast with a young woman or teen, who would have hypogonadism rather than menopause. This is because hypogonadism is an abnormality, whereas menopause is a normal change in hormone levels. In any case, the LH and FSH levels will rise in cases of primary hypogonadism or menopause, while they will be low in women with secondary or tertiary hypogonadism.

Hypogonadism is often discovered during evaluation of delayed puberty, but ordinary delay, which eventually results in normal pubertal development, wherein reproductive function is termed constitutional delay. It may be discovered during an infertility evaluation in either men or women.

Screening males who do not have symptoms for hypogonadism is not recommended as of 2018.[14]

Male primary or hypergonadotropic hypogonadism is often treated with testosterone replacement therapy if they are not trying to conceive.[9] Adverse effects of testosterone replacement therapy include increased cardiovascular events (including strokes and heart attacks) and death.[15] The Food and Drug Administration (FDA) stated in 2015 that neither the benefits nor the safety of testosterone have been established for low testosterone levels due to aging.[16][17] The FDA has required that testosterone pharmaceutical labels include warning information about the possibility of an increased risk of heart attacks and stroke.[16][17]

While historically, men with prostate cancer risk were warned against testosterone therapy, that has shown to be a myth.[18]

Other side effects can include an elevation of the hematocrit to levels that require blood withdrawal (phlebotomy) to prevent complications from excessively thick blood. Gynecomastia (growth of breasts in men) sometimes occurs. Finally, some physicians worry that obstructive sleep apnea may worsen with testosterone therapy, and should be monitored.[19]

Another treatment for hypogonadism is human chorionic gonadotropin (hCG).[20] This stimulates the LH receptor, thereby promoting testosterone synthesis. This will not be effective in men who simply cannot make testosterone anymore (primary hypogonadism) and the failure of hCG therapy is further support for the existence of true testicular failure in a patient. It is particularly indicated in men with hypogonadism who wish to retain their fertility, as it does not suppress spermatogenesis like testosterone replacement therapy does.

For both men and women, an alternative to testosterone replacement is low-dose clomifene treatment, which can stimulate the body to naturally increase hormone levels while avoiding infertility and other side effects that can result from direct hormone replacement therapy.[21] Clomifene blocks estrogen from binding to some estrogen receptors in the hypothalamus, thereby causing an increased release of gonadotropin-releasing hormone and subsequently LH from the pituitary. Clomifene is a selective estrogen receptor modulator (SERM). Generally, clomifene does not have adverse effects at the doses used for this purpose. Clomifene at much higher doses is used to induce ovulation and has significant adverse effects in such a setting.

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Hypogonadism - Wikipedia