|Systematic (IUPAC) name|
|CAS Registry Number|
|Molecular mass||290.440 g/mol|
|(what is this?)|
Androsterone, or 3α-hydroxy-5α-androstan-17-one, is an endogenous steroid hormone and weak androgen with a potency that is approximately 1/7 that of testosterone. In addition, it can be converted to dihydrotestosterone (DHT) from 3α-hydroxysteroid dehydrogenase and 17β-hydroxysteroid dehydrogenase, bypassing conventional intermediates such as androstenedione and testosterone, and as such, can be considered to be a metabolic intermediate in its own right. Androsterone is also known to be an inhibitory androstane neurosteroid, acting as a positive allosteric modulator of the GABAA receptor, and possesses anticonvulsant effects. The unnatural enantiomer of androsterone is more potent as a positive allosteric modulator of GABAA receptors and as an anticonvulsant than the natural form.  Androsterone's 3β-isomer is epiandrosterone, and its 5β-epimer is etiocholanolone. Androsterone is also a possible male pheromone.
It was first isolated in 1931, by Adolf Friedrich Johann Butenandt and Kurt Tscherning. They distilled over 17,000 liters (3,700 imp gal; 4,500 U.S. gal) of male urine, from which they got 50 milligrams (0.77 gr) of crystalline androsterone, which was sufficient to find that the chemical formula was very similar to estrone.
Androsterone is generally considered to be an inactive metabolite of testosterone, which when conjugated by glucuronidation and sulfation allows testosterone to be removed from the body, but it is a weak neurosteroid that can cross into the brain and could have effects on brain function.
Androsterone and its 5β-isomer, etiocholanolone, are produced in the body as metabolites of testosterone. Testosterone is converted to 5α-dihydrotestosterone and 5β-dihydrotestosterone by 5α-reductase and 5β-reductase, respectively. The enzyme 3α-hydroxysteroid dehydrogenase converts the reduced forms to 5α- and 5β-androstanediol, which are subsequently converted by 17β-hydroxyteroid dehydrogenase to androsterone and etiocholanolone, respectively. Androsterone and etiocholanolone can also be formed from androstenedione via the action of 5α- and 5β-reductase forming 5α- and 5β-androstane-3,17-dione which are then converted to androsterone and etiocholanolone by 3α- and 3β-hydroxysteroid dehydrogenase.
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