Beta-endorphin/beta-lipotropin release and gonadotropin secretion after acute exercise in physically conditioned males.

beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) concentrations were measured in the basal state and after acute exercise for 15 min or until exhaustion in 6 physically conditioned male volunteers. Serum concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone and prolactin were also measured in the basal state. In addition, the concentrations of the gonadotropins (LH and FSH) were determined after exercise and the gonadotropin response to gonadotropin releasing hormone was assessed before and after exercise. The data show that acute exercise stimulates the release of both beta-EP and beta-LPH which return to base-line levels within 60 min after exercise. This is in contrast to our previously described results in physically unconditioned male volunteers in whom only beta-LPH release was noted after exercise. Serum LH concentrations declined after exercise reaching nadir values between 60 to 150 min after exercise. As we previously reported in physically unconditioned male volunteers, serum FSH concentrations did not change with exercise and the gonadotropin response to LRH stimulation was uninfluenced by exercise. Serum testosterone and prolactin concentration were within the normal range for healthy adult males. We speculate that the difference in beta-EP release with exercise in physically conditioned and unconditioned males represents a difference in processing of the opioid precursor molecule (pro-opiomelanocortin, POMC) in the two groups.