AR and prostate cancer: Type I and type III 5α-reductase (SRD5A1 and SRD5A3) were discovered to be correlated with DHT generation and AR activation in malignant prostate tumors (Uemura et al., 2008; Godoy et al., 2011), while type II (SRD5A2) is primarily expressed in normal prostate tissues (Thigpen et al., 1993; Chen et al., 1998).