Hypothalamic-pituitary-adrenal axis function in elderly endurance athletes

To explore the effects of repeated episodes of hypercortisolemia on hypothalamic-pituitary-adrenal axis regulation, we studied plasma ACTH and cortisol (CORT) responses to 100 micrograms human CRH (hCRH) in 10 dexamethasone (1.5 mg)-pretreated elderly endurance athletes who had abstained from physical activity for at least 48 h before testing and 13 sedentary age-matched controls. Basal CORT and ACTH levels were indistinguishable between runners and sedentary controls, whereas CORT responses to hCRH were significantly increased in endurance athletes, and ACTH responses tended to be higher in this group. Comparing the dexamethasone/hCRH test results of the runners with those of an age-matched sample of previously studied depressed patients (n = 9), similar hormone responses to CRH challenge were noted. The mechanisms underlying these alterations may either be a stepwise decrease in corticotropic sensitivity to the negative feedback signal leading to a switch to positive glucocorticoid feedback, an enhanced cosecretion of ACTH secretagogues such as vasopressin, or a combination of both. In conclusion, hypothalamic-pituitary-adrenal axis physiology seems to be determined by previous stressful events associated with hypercortisolemia, regardless of its etiology.