SRD5A2, or 5-alpha-reductase 2, is an enzyme that facilitates the conversion of testosterone into dihydrotestosterone (DHT), a more potent androgen. It is primarily expressed in androgen-sensitive tissues such as the prostate gland, hair follicles, and external genitalia. SRD5A2 plays a key role in androgen metabolism and the regulation of androgen signaling. Testosterone, produced mainly in the testes, adrenal glands, and ovaries, serves as the precursor for DHT. By reducing the 4,5 double bond in the A ring of testosterone, SRD5A2 increases DHT’s binding affinity to the androgen receptor (AR).