5α-androstane-3β,17β-diol

5α-Androstane-3β,17β-diol, also called 3β-androstanediol, and often shortened to 3β-diol, is an endogenous steroid hormone. It is a 5α-reduced and 17β-hydroxylated metabolite of dehydroepiandrosterone (DHEA) as well as a 3β-hydroxylated metabolite of dihydrotestosterone (DHT). 3β-Diol is a selective, potent, high-affinity full agonist of the ERβ, and hence, an estrogen. It has higher affinity for this receptor than estradiol. In contrast to ERβ, 3β-diol does not bind to the androgen receptor (AR). 3β-Diol has been reported to also bind to ERα with low nanomolar affinity, with several-fold lower affinity relative to ERβ. Unlike its 3α-isomer, 3α-androstanediol (3α-diol), 3β-diol does not bind to the GABAA receptor.
3β-Diol appears to be the endogenous ligand of ERβ in the prostate gland, and as a result of activation of the ERβ, 3β-diol has antiproliferative effects against prostate cancer cells. Through the ERβ, 3β-diol positively regulates oxytocin neurons and signaling in the paraventricular nucleus of hypothalamus (PVN), and has been found to have antidepressant, anxiolytic, cognitive-enhancing, and stress-relieving effects via this action. Androgens, including testosterone and dihydrotestosterone (DHT), are known to downregulate the hypothalamic-pituitary-adrenal axis, and this has been found to be due in part or full to their conversion into 3β-diol rather than to activation of the AR.
A determination of the circulating levels of 3β-diol in humans found concentrations of 239 ± 76 pg/ml and 82 ± 45 pg/ml of the compound in normal male and female serum, respectively.
An orally active synthetic analogue of 3β-diol, 17α-ethynyl-5α-androstane-3α,17β-diol (HE3235, Apoptone), was formerly under investigation for the treatment of prostate cancer and breast cancer.