How does male hormonal contraception (MHC) work?

MHCs work by stopping the signals and processes that control sperm production. The brain (via the hypothalamus) detects the body's testosterone (T) levels and determines whether to send signals (GnRH, LH, and FSH) to the testes to make more. The amount of T floating around the testis controls sperm production. Giving additional T or similar hormone signals, like androgens and progestins, can trick the brain and prevent it from signaling more T production in the testes. Without high enough levels of T in the testes, sperm production is shut down. The T in the bloodstream remains normal, maintaining male features, like muscle tone and libido.