IMPAIRED PITUITARY HORMONAL RESPONSE TO EXHAUSTIVE EXERCISE IN OVERTRAINED ENDURANCE ATHLETES

The aim of the present prospective longitudinal study was to investiga te the hormonal response in overtrained athletes at rest and during ex ercise consisting of a short-term exhaustive endurance test on a cycle ergometer at an intensity 10% above the individual anaerobic threshol d. Over a period of 19 +/- 1 months, 17 male endurance athletes (cycli sts and triathletes; age 23.4 +/- 1.6 yr; (V)over dot O-2max 61.2 +/- 1.8 mL.min(-1).kg(-1); means +/- SEM) were examined five times on two separate days under standardized conditions. Short-term overtraining s tates (OT, N = 15) were primarily induced by an increase of frequency of high-intensive bouts of exercise or competitions without increase o f the total amount of training. OT was compared with normal training s tates intraindividually (NS, N = 62). During OT, the time to exhaustio n of the exercise test was significantly decreased by 27% on average. At rest and during exercise, the concentrations in plasma and the noct urnal excretion in urine of free epinephrine and norepinephrine were n ot significantly changed during OT. At physical rest, the concentratio ns of (free) testosterone, cortisol, luteinizing hormone, follicle-sti mulating hormone, adrenocorticotropic hormone, growth hormone, and ins ulin during OT were comparable with those during NS. A significantly ( P < 0.025) lower maximal exercise-induced increase of the adrenocortic otropic hormone and growth hormone, as well as a trend for a decrease of cortisol (P = 0.060) and insulin (P = 0.036), was measured. The res ponse of free catecholamines as well as the ergometric performance of an all-out 30-s test was unchanged. Serum urea, uric acid, ferritin, a nd activity of creatine kinase showed no differences between condition s. In conclusion, the results confirm the hypothesis of a hypothalamo- pituitary dysregulation during OT expressed by an impaired response of pituitary hormones to exhaustive short-endurance exercise.