5-Alpha reductase deficiency: a 40-year retrospective review

5-Alpha reductase is an enzyme responsible for the conversion of testosterone to dihydrotestosterone. This key enzyme is responsible for triggering masculinization of the male external genitalia. Discovery of 5-alpha reductase deficiency as a syndrome of disordered male sexual development led to our molecular understanding of the role that this key enzyme plays in male sexual differentiation. This article will review the clinical and molecular history behind the discovery of 5-alpha reductase deficiency.

Three different genes encoding for 5-alpha reductase have been identified, with 5-alpha reductase type 2 being implicated in disordered male sexual development.

The discovery of 5-alpha reductase deficiency has not only shed light on the crucial role of 5-alpha reductase, testosterone, and dihydrotestosterone in male sexual differentiation but it also has facilitated the discovery of novel therapeutic applications of 5-alpha reductase inhibitors in clinical practice.