The Acute and Chronic Effects of Marathon Training on the Function of the Hypothalamic - Pituitary - Gonadal Axis of Male Runners (Reproductive System, Testosterone, Gonadotropins).

The long-term and acute effects of marathon running on the reproductive system of male runners, specifically the hypothalamic-pituitary-gonadal axis, is not well understood. While evidence is available for women runners demonstrating alterations of this axis resulting in menstrual cycle disorders, such evidence is lacking for men. The purpose of the present investigation was to examine the effect of marathon training on the hypothalamic-pituitary-gonadal axis of competitive male marathon runners. Both the cumulative and acute effects of training were examined by measuring testosterone, luteinizing hormone (LH), and follicle stimulating hormone (FSH) concentrations, and the secretory pattern of LH during basal conditions and during a two-hour run. In addition, pituitary and testicular sensitivity was examined with the administration of gonadotropin releasing hormone (GnRH) and human chorionic gonadotropin (hCG), respectively. While there was no cumulative effect of marathon training on testosterone concentrations of the runners, the hypothalamic-pituitary axis was affected. The LH pulse frequency was significantly lower, and mean LH concentrations were significantly higher in the runners. In response to stimulation with three increasing doses of GnRH, the percent rise in LH was lower in the runners than in the controls, indicating some impariment of the hypothalamic-pituitary axis. There were no other differences between groups for testosterone, FSH, or prolactin concentrations, nor for LH pulse amplitude. In addition, testicular responsiveness to a bolus injection of hCG was similar for both groups. The two-hour exercise bout had little effect on the hypothalamic-pituitary-gonadal axis. Testosterone concentrations increased significantly by 40 minutes of running and remained elevated for the duration of the run. However, in the absence of any alterations in LH and FSH concentrations, the rise was due more to decreased metabolic clearance of testosterone than to increased testosterone secretion. The pulsatile secretion of LH and FSH was unaffected by the exercise bout.Ph.D.Physical educationUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160690/1/8520937.pd