β-Endorphin/β-lipotropin release and gonadotropin secretion after acute exercise in physically conditioned males

Abstract

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.

Beta-endorphin immunoreactivity during high-intensity exercise with and without opiate blockade

“…Such increases in b-endorphin concentration were observed early in exercise (i.e., 5±10 min.). Some investigators who also employed vigorous but less intense protocols (i.e., 80±85% of maximal HR) failed to show any signi®cant changes in b-endorphin concentration during exercise (Bullen et al 1984;Elias et al 1989). Moreover, other investigators have also reported no signi®cant changes in b-endorphin concentration during exercise of low to moderate intensity (Goldfarb et al 1991;McMurray et al 1987).…”

Pituitary-gonadal response to gonadotropin-releasing hormone stimulation is enhanced in men after strenuous physical exercise

“…However, infertility is uncommon in male athletes (9). Attenuated LH response to GnRH stimulation has been shown in long-distance runners (11), but the gonadotropin response to GnRH stimulation is reported to be uninfluenced by acute short-term exercise to exhaustion (14). Also, the overtraining syndrome has been related to hypothalamic dysfunction: ACTH, GH and prolactin responses to insulin-induced hypoglycemia was attenuated in overtrained athletes (15).…”

The Male Reproductive System, Exercise, and Training

“…Alterations in circulating ~-endorphin levels have been considered responsible for short-term and chronic exercise-associated suppression of the HPG axis in both men and women. This has been difficult to prove, since opiate antagonism does not prevent the exercise-induced decrease in LH observed by some, but by no means all investigators (14,49,52,53,57,58). Gonadotropin response to GnRH has been reported as reduced and increased following prolonged, exhaustive exercise (53,59).…”

“…GnRH-induced LH response appears to be impaired (58). No evidence has supported increased opioidergic tone as being important in the generation of GnRH-LH suppression in athletes, but the effects of catecholamines have received little attention (57,102). Chronic elevation of serum cortisol levels has been associated with overtraining, but cortisol levels are usually nonnal in male endurance-trained runners (104).…”