5-alpha-reductase (5α-reductase)

5-alpha-reductase Overview

5-alpha-reductase (5α-reductase) is a family of membrane-bound enzymes that catalyze the NADPH-dependent reduction of the Δ4,5 double bond in steroid substrates, most notably converting testosterone into dihydrotestosterone (DHT), a more potent androgen. This reaction is crucial for normal male sexual differentiation and development, as DHT plays an essential role in forming external genitalia before birth and influences secondary male characteristics later in life. There are three known human isozymes: Type 1, Type 2, and Type 3. Each isozyme has distinct tissue distributions and physiological roles. Type 2 is especially important for male sexual differentiation during embryogenesis, while type 1 predominates in skin and liver. Type 3 also participates in N-glycosylation via dolichol phosphate formation. Inhibitors such as finasteride target types 1/2 isoforms selectively or non-selectively. Therapeutic uses include treatment of BPH and hair loss; ongoing research explores broader implications due to CNS effects from altered neurosteroid synthesis.

Mechanism of Action

Inhibition of 5-alpha-reductase, reducing DHT levels

Biological Functions

Safety Considerations

Interacting Drugs