Hormonal responses to the stress of exercise.

Exercise stimulates the hypothalamic-pituitary-adrenal and renin-angiotensin-aldosterone axes and causes growth hormone and prolactin release in an intensity-dependent fashion. Activation of the different endocrine responses examined occur at different exercise intensities. Subjects of differing training status respond similarly to matched exercise intensities. Highly trained subjects have elevated basal concentrations of ACTH and cortisol and a blunted response to exogenous corticotropin releasing hormone. These data are compatible with mild sustained hypercortisolism in highly trained runners.