ANNUAL PATTERNS OF LUTEINIZING-HORMONE, FOLLICLE-STIMULATING-HORMONE,TESTOSTERONE AND INHIBIN IN NORMAL MEN

Reproductive functions in most animals demonstrate seasonal fluctuatio ns that allow young to be born at a time of the year favourable for th eir survival. Whether there is a seasonal change in the human reproduc tive system is unclear. fn the present study, we measured serum concen trations of luteinizing hormone, follicle stimulating hormone, testost erone and inhibin in the same 16 normal men sampled monthly for 1 year . A statistically significant increase in all four measured hormones w as found in June, with a nadir in August. Our findings suggest that a circannual rhythm of gonadotrophins and testicular hormones exists in normal men. The mechanism leading to this rhythm and the importance of the rhythm in human biology are unknown.