3-oxo-5-alpha-steroid 4-dehydrogenase 2 (SRD5A2) (SRD5A2)

Type 2 5-alpha reductase, also known as 3-oxo-5-alpha-steroid 4-dehydrogenase 2, is a critical microsomal enzyme encoded by the SRD5A2 gene [2, 7]. It is predominantly expressed in the prostate, seminal vesicles, and hair follicles, where it catalyzes the irreversible conversion of testosterone into the more potent androgen, dihydrotestosterone (DHT) [1, 3, 4]. This enzymatic process is vital for normal male sexual differentiation and the maintenance of androgen-dependent tissues [15]. Pathologically, elevated DHT levels produced by this enzyme contribute to the development of benign prostatic hyperplasia (BPH) and androgenetic alopecia (male-pattern baldness) [9, 12]. Conversely, loss-of-function mutations in the SRD5A2 gene result in 5-alpha reductase deficiency, a condition characterized by ambiguous genitalia in genetic males [15, 19]. Therapeutic targeting of Type 2 5-alpha reductase with inhibitors such as finasteride and dutasteride is widely used to manage BPH and hair loss by lowering systemic and local DHT concentrations [12, 14]. Notable safety concerns for these inhibitors include sexual side effects and potential teratogenic risks to male fetuses [14, 18].

Other names

Steroid 5-alpha-reductase 25-alpha-reductase type 25 alpha-SR2SR type 2S5AR 2Type II 5-alpha reductase

Inhibition of the conversion of testosterone to the more potent androgen dihydrotestosterone (DHT) by blocking the 5-alpha reductase enzyme.