Dihydrotestosterone (DHT), or 5?-dihydrotestosterone (5?-DHT), also known as 5?-androstan-17?-ol-3-one, is an endogenous androgen sex steroid and hormone. The enzyme 5?-reductase catalyzes the formation of DHT from testosterone in certain tissues including the prostate gland, seminal vesicles, epididymides, skin, hair follicles, liver, and brain. This enzyme mediates reduction of the C4-5 double bond of testosterone. Relative to testosterone, DHT is considerably more potent as an agonist of the androgen receptor (AR).