Figure 5. The development of male internal genitalia in the human embryo. The stabilization and differentiation of the Wolffian ducts are mediated by testosterone synthesized by the fetal Leydig cells. The enzyme 5α-reductase 2 converts testosterone to dihydrotestosterone (DHT). The Wolffian ducts differentiate into epididymis, vas deferens and seminal vesicles. DHT contributes to prostate differentiation.