5α-Reductase enzyme (5α-Reductase)

The 5α-reductase enzyme is a family of enzymes responsible for catalyzing the irreversible reduction of testosterone into dihydrotestosterone (DHT), a more potent androgen that plays a critical role in male sexual differentiation and development as well as in several androgen-dependent conditions. There are three known isoforms—type 1, type 2, and type 3—encoded by SRD5A genes. The enzyme is expressed in various tissues including reproductive organs, skin, liver, and nervous system. Inhibition or deficiency of this enzyme leads to significant clinical consequences related to androgen action such as ambiguous genitalia or reduced secondary male characteristics at birth.

Other names

3-oxo-5α-steroid 4-dehydrogenaseSteroid 5α-reductaseSRD5A (refers to gene family)Five alpha reductaseTestosterone reductase (less common)

Finasteride and dutasteride are competitive inhibitors of the 5α-reductase enzyme, blocking the conversion of testosterone to DHT, thereby reducing DHT levels in tissues.