5β-Dihydrotestosterone
5β-Dihydrotestosterone, also known as 5β-androstan-17β-ol-3-one or as etiocholan-17β-ol-3-one, is an etiocholane steroid as well as an inactive metabolite of testosterone formed by 5β-reductase in the liver and bone marrow and an intermediate in the formation of 3α,5β-androstanediol and 3β,5β-androstanediol and, from them, respectively, etiocholanolone and epietiocholanolone. Unlike its isomer 5α-dihydrotestosterone, 5β-DHT either does not bind to or binds only very weakly to the androgen receptor. 5β-DHT is notable among metabolites of testosterone in that, due to the fusion of the A and B rings in the cis orientation, it has an extremely angular molecular shape, and this could be related to its lack of androgenic activity. 5β-DHT, unlike 5α-DHT, is also inactive in terms of neurosteroid activity, although its metabolite, etiocholanolone, does possess such activity.
