Adrenocortical responsiveness to graded ACTH infusions in normal young and elderly human subjects

The responses of plasma cortisol, aldosterone, dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S) to graded ACTH infusions (from 50 mU/h to 1,000 mU/h) in elderly subjects were compared with those in young subjects. There were no significant differences between young and elderly subjects in terms of the levels of plasma cortisol during ACTH infusion. The increment in median serum cortisol increase observed in elderly subjects was also equal to that found in young subjects. Plasma aldosterone concentration showed a gradual increase in response to ACTH infusion in both young and elderly individuals. There was no significant difference between the response of young and aged subjects. Significant increases in serum DHEA in response to ACTH infusion were observed in both young and aged individuals, however, the median increase of serum DHEA (delta DHEA) in the elderly subjects was markedly lower than that in the young ones. Serum DHEA-S concentrations prior to ACTH infusion were significantly lower in the elderly subjects. With graded infusions of ACTH, plasma DHEA-S concentrations in young subjects tended to increase gradually, whereas there was no significant increase in plasma DHEA-S concentrations in the elderly. These results are indicative that the responses of adrenal androgens in elderly subjects to small, graded doses of ACTH infusion are preferentially impaired; however, the responses of cortisol and aldosterone are well maintained.