ABSTRACT
Efforts are underway to develop new methods of contraception for men. The most promising approach to male contraceptive development is hormonal and involves the administration of testosterone. When testosterone is administered to a man, it functions as a contraceptive by suppressing the secretion of luteinizing hormone and follicle-stimulating hormone from the pituitary gland, thereby depriving the testes of the signals required for spermatogenesis. After two to three months of treatment, low levels of gonadotropins lead to markedly decreased sperm counts and effective contraception in a majority of men. In many clinical trials, male hormonal contraception has proven to be free from serious adverse effects and is well-tolerated by men. In addition, sperm parameters uniformly normalize when treatment is discontinued. The main drawback to this approach is the observation that spermatogenesis is not suppressed to zero in all men, meaning that some potential for fertility persists. Because of this, recent studies have combined testosterone with progestogens and/or gonadotropin-releasing antagonists to synergistically suppress pituitary gonadotropins and improve suppression of spermatogenesis. Current combinations of testosterone and progestogens severely suppress spermatogenesis without severe side effects in 80-90% of men, with significant suppression in the remainder of individuals. Recent trials with newer, long-acting forms of injectable testosterone, such as testosterone undecanoate, which can be administered every 8-10 weeks, combined with progestogens, administered either orally or by long-acting implant, have yielded promising results and may soon result in the marketing of a safe, reversible and effective hormonal contraceptive for men.
