Dihydrotestosterone (commonly abbreviated to DHT), or 5α-dihydrotestosterone (5α-DHT), also known as androstanolone (5α-androstan-17β-ol-3-one) as well as 17β-hydroxy-5α-androstan-3-one, is a sex steroid and androgen hormone. The enzyme 5α-reductase synthesizes DHT in the prostate, testes, hair follicles, and adrenal glands. This enzyme reduces the 4,5 double-bond of the hormone testosterone.