Figure 1: Schematic principle of the endocrine mechanism of hormonal male contraception. Testosterone or the androgen used suppresses GnRH release as well as the production of gonadotropins. This effect is augmented by additional use of a progestin or a long-acting GnRH antagonist. Testicular functions mediated by Leydig cells and Sertoli cells are attenuated and spermatogenesis is inhibited. Systemic androgen activity is maintained due to the administered androgen. DHT: double hydrogen testosterone; FSH: follicle-stimulating hormone; GnRH: gonadotropin-releasing hormone; LH: luteinizing hormone.