Among these genes, steroid 5α-reductase 1 (SRD5A1) and steroid 5α-reductase 2 (SRD5A2) encode 5α-reductase type 1 and type 2, respectively, which are involved in testosterone metabolism and have been associated with an increased risk of prostatic hyperplasia [37, 38]. This evidence concerns the gene SRD5A1 and benign prostatic hyperplasia.