Effects of human chorionic gonadotropin administration on testicular testosterone secretion during prolonged exercise

A decrease in testosterone concentrations in men after prolonged exercise has been confirmed in many studies, although testosterone responses are somewhat variable and seem to depend on the duration and intensity of the exercise (1, 2). The decline in serum testosterone levels after prolonged exercise generally is ascribed to a decrease in the rate of secretion caused by a decrease in testicular blood flow, an increase in body temperature, and an increase in plasma concentrations of prolactin and cortisol. Data have shown that testicular secretion of testosterone may be influenced by prolonged exercise (3), but no direct evidence has yet been adduced.