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Towards a pill for men

This review outlines the prospects for the development of an oral contraceptive for men. Male fertility may be temporarily interrupted by interference with the hormonal control of the testis, a direct action of agents on spermatogenesis or by interference with the acquisition of fertilizing ability once sperm leave the testis. Spermatogenesis can be suppressed successfully by the antigonadotrophic action of androgens, progestagens or oestrogens used alone or in combination and the results of these studies provide the basis for the future development of an oral contraceptive. Achievement of this goal will require the adjustment of doses to provide adequate spermatogenic suppression without loss of libido. Preliminary studies indicate that compounds which are capable of selectively suppressing FSH levels do exist and may enable spermatogenic suppression without alteration of androgenic function. The majority of substances that act directly on the testis appear to be too toxic to suppress spermatogenesis reversibly. However, recent studies with 5-thio-D-glucose have demonstrated inhibition of spermatogenesis which is reversible on ceasing to take the agent. This material appears non-toxic in the doses required and does not alter libido and potency. Interference with the epididymal maturation of sperm is feasible using α-chlorohydrin but toxic effects have prevented its use in primates. Analogues with similar actions have been identified which cause infertility but toxicity data have not been fully evaluated.