Androgen
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What are androgens?
Androgens are a group of hormones that primarily affect the growth and development of the male reproductive system. The testes mainly produce the most active androgen, testosterone. The adrenal cortex produces other androgens in smaller amounts to support testosterone functions.
Androgens are needed for the development of the male reproductive system, the formation of sperm cells, and the maintenance of sexual interest and behavior. These hormones also influence the growth of pubic, facial, and chest hair, deepen the voice, enhance bone growth, and increase muscle fiber. Women produce androgens in smaller amounts, which are converted to estrogens. Androgens in women may contribute to bone growth and libido.
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What is the main function of androgen hormones in the body?
Androgens are a group of hormones that primarily affect the growth and development of the male reproductive system. The most important androgen is testosterone, mainly produced in the testes.
Androgens are needed for the development of the male reproductive system, the formation of sperm cells, and the maintenance of sexual interest and behavior. These hormones also influence the growth of facial and pubic hair, the thickening of vocal cords, bone growth, and muscle fiber thickness. Androgens stimulate kidney size, increase protein in bone tissue, boost red blood cell regeneration, and increase the activity of sweat and oil-producing glands.
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Which organs produce androgens?
Androgens are a group of hormones that affect the development of the male reproductive system. The primary and most active androgen is testosterone, produced by the testes.
Other androgens that support testosterone are mainly produced in relatively small quantities by the adrenal cortex, the outer portion of the adrenal glands. In women, the ovaries produce testosterone and androstenedione, while the adrenal glands produce DHEA and DHEA sulfate.
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How do androgens affect male and female bodies differently?
Androgens, present in both sexes, play distinct roles. In males, these hormones are crucial for developing the reproductive system, producing sperm, and maintaining sexual desire. They also influence secondary sexual characteristics, such as hair growth, voice deepening, muscle mass, and bone growth.
In females, androgens are converted into estrogens and are associated with bone growth and libido. However, excess androgen production in women can lead to hirsutism (excess hair growth), menstrual irregularities, and virilization, which includes frontal balding, voice deepening, and increased muscle mass. Androgen excess in women is often linked to conditions like polycystic ovary syndrome (PCOS).
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What are some common health conditions related to androgen imbalance?
Androgen imbalance, where there is an excess of androgen, can lead to several health conditions, especially in women. Mild excess can cause hirsutism (excess hair growth), while increasing excess can lead to irregular or ceased menstrual periods (oligomenorrhea or amenorrhea) and virilization.
Virilization symptoms include frontal balding, deepening of the voice, acne, clitoral enlargement, and increased muscle mass. A common cause of androgen excess is polycystic ovary syndrome (PCOS), characterized by menstrual disorders, hirsutism, and sometimes ovarian cysts. Congenital adrenal hyperplasia can also cause androgen excess, leading to virilization in newborn girls and precocious sexual development in boys.
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How is androgen production regulated in the human body?
In males, androgen production, primarily testosterone, is regulated by the hypothalamic-pituitary-testes axis. Gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the anterior pituitary to produce luteinizing hormone (LH). LH acts on Leydig cells in the testes to stimulate testosterone production.
Testosterone inhibits the secretion of GnRH and LH, maintaining testosterone concentrations within a narrow range. Follicle-stimulating hormone (FSH), also produced by the pituitary, and testosterone stimulate spermatogenesis. Sertoli cells produce inhibin, which inhibits FSH secretion.
In females, androgens are produced in smaller amounts by the ovaries and adrenal glands. In women, about half of the daily production of androgen comes from the ovaries in the form of testosterone and the less active androstenedione, while the remainder comes from the adrenal glands, mostly as DHEA and DHEA sulfate, which are converted to androstenedione and testosterone in other tissues.
8 Britannica Sources- adrenal gland: Adrenal cortex
- gonadotropin
- congenital adrenal hyperplasia: Types and clinical manifestation
- testis: Regulation of testicular function
- human sexual activity: Genetic and hormonal factors
- hormone: Luteinizing hormone (interstitial-cell-stimulating hormone)
- steroid: Sex hormones
- androgen: Androgen excess in women
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Androgen, any of a group of hormones that primarily influence the growth and development of the male reproductive system. The predominant and most active androgen is testosterone, which is produced by the male testes. The other androgens, which support the functions of testosterone, are produced mainly by the adrenal cortex—the outer portion of the adrenal glands—and only in relatively small quantities.
Production
In males the interstitial cells of Leydig, located in the connective tissue surrounding the sperm-producing tubules of the testes, are responsible for the production and secretion of testosterone. In male animals that breed only seasonally, such as migratory birds and sheep, Leydig cells are prevalent in the testes during the breeding season but diminish considerably in number during the nonbreeding season. The actual secretion of androgens by these cells is controlled by luteinizing hormone (LH) from the pituitary gland.
The adrenal production of androgens is of importance to several physiological processes. Certain adrenal androgens—androstenedione, dehydroepiandrosterone (DHEA), and dehydroepiandrosterone sulfate (DHEA sulfate)—can be converted to testosterone in other tissues.
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Physiological effects in males
Only a very small amount of androgen is secreted before puberty. In both girls and boys, puberty is associated with an increase in adrenal androgen production. This “adrenarche” contributes to pubertal maturation, particularly growth of axillary and pubic hair. Androgens also are needed for the development of the male reproductive system. Males that have been castrated prior to adolescence and sexual maturity require injections of testosterone to develop functioning adult reproductive organs. Androgens given to normal males tend to increase the size of the reproductive organs. In contrast, castration performed on males that have already reached maturity causes the organs to shrink and to stop functioning. Androgens also are necessary for the formation of sperm cells and for the maintenance of sexual interest and behaviour.
Other effects of androgens on the male body are diversified. The growth of pubic hair and of facial and chest hair and the regression of scalp hair, or baldness, are influenced by androgens. During adolescence, androgens lengthen and thicken the male vocal cords, causing voice deepening; they also enhance bone growth and increase the number and thickness of muscle fibres in the male body. Other growth patterns that androgens stimulate are kidney weight and size, the increase of protein in bone tissue, the regeneration of red blood cells (erythrocytes), the presence of pigments in the skin, and the increased activity of sweat and sebaceous (oil-producing) glands.
Androgen excess in women
Women produce about one-twelfth as much androgen as men. Androgens are essential precursors of estrogens, and no estrogens can be produced without them. Whether androgens have physiological actions in women is less clear. Some evidence suggests that androgens contribute to bone growth and libido. Mild androgen excess in women results in excess hair growth (hirsutism) that occurs all over the body but is most often noted on the face. With increasing androgen excess, menstrual periods become irregular (oligomenorrhea) and eventually cease (amenorrhea), and women are virilized. The manifestations of virilism include frontal balding, deepening of the voice, acne, clitoral enlargement, and increased muscle mass.
In women about half of the daily production of androgen comes from the ovaries in the form of testosterone and the less active androstenedione. The remainder comes from the adrenal glands, mostly as DHEA and DHEA sulfate, which are converted to androstenedione and testosterone in other tissues. The tissues capable of these conversions include the skin, fat, muscle, and brain. Some of these tissues are also capable of converting androstenedione to the more potent testosterone. Some of the testosterone produced in this way returns to the circulation to act at distant sites, but high concentrations may accumulate in key local areas such as hair follicles.
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In women excess production of androgen can occur as a result of adrenal disorders, ovarian disorders, ingestion or injection of androgens, and perhaps disorders of fat or other nonendocrine tissues. The adrenal causes of excess production of androgens are Cushing syndrome, congenital adrenal hyperplasia, and adrenal tumours. Tumours (including cancers) of the interstitial cells and other cells of the ovary are a rare cause of androgen excess in women.
A far more common cause of excess production of androgens in women is polycystic ovary syndrome (PCOS; also called Stein-Leventhal syndrome). This syndrome is characterized by excess androgens and the presence of a menstrual disorder. Androgen excess often manifests as hirsutism, with or without increased serum concentrations of one or more androgens. Some women have increased serum androgen concentrations and no hirsutism. A variety of menstrual disorders have been associated with PCOS, including oligomenorrhea, amenorrhea, anovulation, and infertility. An ultrasound may reveal multiple ovarian cysts. Many women with this syndrome are obese. Another characteristic feature of PCOS is tissue resistance to the action of insulin. This is expected in obese women, but it is also present in nonobese women with the syndrome. Insulin resistance leads to an increase in insulin secretion (hyperinsulinemia), which is thought to stimulate ovarian androgen production. Hyperinsulinemia also decreases the production of sex hormone-binding globulin so that more of the testosterone in the serum is free and accessible to the tissues. In addition, the conversion of androgens to estrogens in adipose tissue is increased (particularly in obese women), which leads to a small sustained increase in the secretion of luteinizing hormone and to the suppression of ovulation.