Androgen

Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. This includes the activity of the accessory male sex organs and development of male secondary sex characteristics. Androgens, which were first discovered in 1936, are also called androgenic hormones or testoids. Androgens are also the original anabolic steroids. All natural androgens are steroid derivatives of androstane (19-carbon tetracyclic hydrocarbon nucleus, C19H32). They are also the precursor of all oestrogens, the female sex hormones. The primary and most well-known androgen is testosterone.

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A subset of androgens, adrenal androgens, includes any of the 19-carbon steroids synthesized by the adrenal cortex, an adrenal gland, that function as weak steroids or steroid precursors, including dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), and androstenedione.

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Besides testosterone, other androgens include:

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• Dehydroepiandrosterone (DHEA): a steroid hormone produced from cholesterol in the adrenal cortex, which is the primary precursor of natural estrogens. DHEA is also called dehydroisoandrosterone or dehydroandrosterone.
• Androstenedione (Andro): an androgenic steroid, which is produced by the testes, adrenal cortex, and ovaries. While androstenediones are converted metabolically to testosterone and other androgens, they are also the parent structure of estrone. Use of androstenedione as an athletic or body building supplement has been banned by the International Olympic Committee.
• Androstanediol: the steroid metabolite that is thought to act as the main regulator of gonadotropin secretion.
• Androsterone: a chemical by-product created during the breakdown of androgens, or derived from progesterone, that also exerts minor masculinising effects, but with one-seventh the intensity of testosterone. It is found in approximately equal amounts in the plasma and urine of both males and females.
• Androstenolone: an androgenic steroid secreted by the adrenal cortex and testes, which is a major precursor of testosterone, but is even weaker than androsterone.
• Dihydrotestosterone (DHT): a metabolite of testosterone that is actually a more potent androgen in that it binds more strongly to androgen receptors.

Reduced ability of a XY karyotype fetus to respond to androgens can result in one of several problems, including infertility and several forms of intersex conditions. See androgen insensitivity syndrome (AIS).

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See also: andrology, antiandrogen

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Steroid: A steroid is a lipid characterized by a carbon skeleton with four fused rings. Different steroids vary in the functional groups attached to these rings. Hundreds of distinct steroids have been identified in plants and animals. Their most important role in most living systems is as hormones....

Hormone: A hormone (from Greek horman - "to set in motion") is a chemical messenger from one cell (or group of cells) to another. All multicellular organisms produce hormones (including plants - see article phytohormone)....

Androgen receptor: The androgen receptor is an intracellular steroid receptor that specifically binds testosterone and dihydrotestosterone,- it has two main forms, A and B, that differ in their molecular weight....