Testosterone is produced by the Leydig cells of the testes, which also produce (in lesser amounts) androstenedione, D5-androstenediol, dihydrotestosterone and oestradiol. While testosterone itself appears to produce development of the male body habitus and to change the male voice, 5a reduction of testosterone to form dihydrotestosterone within target cells is the factor that causes phallic development, prostate enlargement, temporal hair recession and beard growth in males. In females, testosterone is derived mainly from extraglandular conversion of ovarian androstenedione.
