Suppression and Partial Recovery of Hypothalamic-Pituitary-Testicular Axis Hormones in Ultraendurance Athletes

In men, the hypothalamic-pituitary-testicular (HPT) axis controls the secretion of testosterone, which is a major anabolic hormone. Physical exercise affects the entire axis and suppresses testosterone concentrations by complex, multilevel mechanisms. These involve hormones of the hypothalamic-pituitary-adrenal (HPA) axis such as corticotropin-releasing hormone (CRH), beta-endorphin, and cortisol. After the exercise, the HPT axis recovers, however the time course and degree of recovery is not known. This is particularly relevant to the evaluation of athletes for possible doping when examined during and after a bout of strenuous exercise. PURPOSE: To examine the influence of a long distance, endurance exercise on the HPT axis and the secretion of testosterone in order to estimate their influence when evaluating athletes for doping. METHODS: In 16 male athletes participating in the ultradistance foot race of the 246 Km "Spartathlon" (continuous, prolonged, brisk exercise for up to 36 hours), we measured circulating concentrations of testosterone, DHEAS, FSH, LH, and cortisol before the race, at the end of the race and 48h postrace. For the measurements we employed immunochemiluminescence (Bayer Centaur) and chemiluminescence (Nichols Diagnostics) techniques. RESULTS: Testosterone, FSH and LH decreased dramatically at the end of the race, compared with the levels before the race (108.4±17.7 ng/dL, 2.6±0.4 IU/L and 1.7±0.2 IU/L versus 460.5±34.2 ng/dL, 4.4±0.5 IU/L and 3.9±0.4 IU/L, respectively. Testosterone only partially recovered 48 hours postrace to about half the prerace values (233.7±18.1 ng/dL). The HPA axis hormone DHEAS and cortisol levels increased significantly at the end of the race (294±40.8 μg/dL and 31.1±2.5 μg/dL versus 162.9±17.7 μg/dL and 13.9±1.1 μg/dL, respectively, and returned to normal 48h postrace. CONCLUSION: The observed alterations of hypothalamic-pituitary-testicular axis hormones found in ultramarathon runners, suggest that prolonged exercise suppresses testosterone which remains partially suppressed for at least 48 hours, even after the HPA axis has recovered. We propose that each exercise paradigm will have a distinct pattern of hormonal response and recovery and should be taken into account when evaluating athletes for doping.