3β-Androstanediol
3β-Androstanediol, also known as 5α-androstane-3β,17β-diol, and sometimes shortened in the literature to 3β-diol, is an endogenous steroid hormone and a metabolite of androgens like dehydroepiandrosterone (DHEA) and dihydrotestosterone (DHT). Biological activity. 3β-Androstanediol 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-androstanediol does not bind to the androgen receptor (AR). 3β-Androstanediol has been reported to also bind to ERα with low nanomolar affinity, with several-fold lower affinity relative to ERβ. It  has approximately 3% and 7% of the affinity of estradiol at the ERα and ERβ, respectively. Unlike 3α-androstanediol, 3β-androstanediol does not bind to the GABA receptor. 3β-Androstanediol may be the primary endogenous ligand of ERβ in the prostate gland, and as a result of activation of the ERβ, 3β-androstanediol has antiproliferative effects against prostate cancer cells. Through the ERβ, 3β-androstanediol positively regulates oxytocin neurons and signaling in the paraventricular nucleus of hypothalamus, and has been found to have antidepressant, anxiolytic, cognitive-enhancing, and stress-relieving effects via this action. Androgens, including testosterone and 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-androstanediol rather than to activation of the AR. Biochemistry. 3β-Androstanediol is a 5α-reduced and 17β-hydroxylated metabolite of dehydroepiandrosterone (DHEA) as well as a 3β-hydroxylated metabolite of DHT (and by extension of testosterone). A determination of the circulating levels of 3β-androstanediol in humans found concentrations of 239 ± 76 pg/ml and 82 ± 45 pg/ml of the compound in normal male and female serum, respectively. 3β-Androstanediol shows high  affinity for sex hormone-binding globulin (SHBG), similar to that of DHT. Chemistry. 3β-Androstanediol, also known as 5α-androstane-3β,17β-diol, is a naturally occurring androstane steroid and a structural analogue of DHT (5α-androstan-17β-ol-3-one). A notable positional isomer of 3β-androstanediol is 3α-androstanediol. 17α-Ethynyl-3β-androstanediol is a 17α-substituted derivative of 3β-androstanediol and is an estrogen similarly.