In healthy young and elderly adults, hypothalamic-pituitary-adrenocortical axis reactivity (HPA AR) varies with increasing pharmacological challenge and with age, but not with gender.

BACKGROUND: Hypothalamic-pituitary-adrenocortical axis reactivity (HPA AR) is the key indicator of the psychophysiological response to stress. The HPA AR may vary with age and gender. To investigate these factors concurrently, the aims of the present study were to observe HPA AR (plasma ACTH and plasma cortisol) in response to a pharmacological challenge (dexamethasone/corticotropin releasing hormone test: DEX/CRH-test) and as a function of age and gender.
METHOD: 19 young (10 females and 9 males; mean age = 24.05 years) and 23 elderly (11 females and 12 males; mean age = 71.61 years) healthy volunteers took part in the study. To assess HPA AR, participants underwent the combined DEX/CRH test applied with the following DEX doses: 0.75, 1.5, and 3.0 mg, respectively.
RESULTS: A dose-dependent response was observed in young adult participants, but not in elderly participants. With increasing DEX doses, ACTH and cortisol values decreased in young adult participants, while the decrease was blunted among elderly compared to young adult participants. No differences were observed for gender.
CONCLUSIONS: Results point to diminished HPA axis sensitivity as an effect of normal aging, irrespective of gender. Therefore, altered HPA regulation in old age should be taken into account for developing new therapeutic approaches acting on the HPA axis and its receptor mechanisms.