Steroid 5-alpha-reductase (SRD5A) (5α-reductase)

Steroid 5-alpha-reductase (5α-reductase) is a membrane-bound enzyme that catalyzes the NADPH-dependent conversion of testosterone into the more potent androgen, dihydrotestosterone (DHT) (UniProt P18405, P31213). It exists in two major isoforms: Type 1 (SRD5A1), found primarily in the skin, liver, and sebaceous glands, and Type 2 (SRD5A2), which predominates in the prostate and hair follicles (StatPearls, 5-Alpha Reductase Inhibitors). This enzyme plays a critical role in male sexual development and the pathophysiology of androgen-dependent conditions. Excessive DHT production is a primary driver of benign prostatic hyperplasia (BPH) and androgenetic alopecia (male pattern baldness) (PubMed PMID: 15116006). Therapeutic strategies involve the use of 5-alpha-reductase inhibitors (5ARIs) like finasteride and dutasteride to lower systemic and local DHT levels. While effective, these drugs are associated with side effects such as sexual dysfunction and must be avoided during pregnancy due to risks of fetal genital malformation (NIH PubChem CID 5901).

Other names

3-oxo-5-alpha-steroid 4-dehydrogenaseSRD5A1SRD5A25-alpha-reductase5AR

Competitive inhibition of the 5-alpha-reductase enzyme isoforms, which blocks the conversion of testosterone to dihydrotestosterone (DHT), thereby reducing androgenic stimulation in target tissues (StatPearls).