Discordant secretions of ACTH and cortisol: an observation indicating multifactoral regulation of adrenal function.

To test the long-standing concept that secretion of adrenal glucocorticoids is solely dependent upon plasma level of adrenocorticotropic hormone (ACTH), we collected sequential blood samples from normal subjects and patients with pituitary-adrenal axis disorders at 30-min intervals for 24 hours and analyzed for both the plasma ACTH and cortisol profiles. In a majority of time points, the changes of cortisol levels coincided with those of ACTH. However, in all individuals tested so far, on more than 24 per cent of occasions, plasma cortisol rose together with a declining or fell with an elevating plasma ACTH level, that indicates a secretory discordance between these two hormones. These discordant patterns cannot be explained simply by the ACTH-stimulatory and cortisol-feedback inhibitory mechanisms. Since a generalized quantitative relationship between the overall profiles of plasma ACTH and cortisol did exist and the mutually regulatory pathways between pituitary and adrenal functions were mostly observable, there were no other known reasons explaining why these frequent and unsynchronized secretory activities should happen. Our observation reveals that cortisol secretion is probably under some other minor but normal influences in addition to the major regulatory action of ACTH.