Plasma Adrenocorticotropin, Cortisol, and Aldosterone Responses to Corticotropin-Releasing Factor:Modulatory Effect of Basal Cortisol Levels

Abstract

Two hundred micrograms of corticotropin-releasing factor (CRF) were administered as an iv bolusinjection to 10 normal subjects (5 men and 5 women). Mean plasma ACTH levels rose significantly (P< 0.0005, by Friedman's nonparametric analysis of variance) from a basal value of 27± 5 pg/ml (mean ± SEM) to a peak value of 63 ± 8 pg/ml 30 min after CRF administration. This ACTH response was followed by a rise in plasma mean cortisol levels (P < 0.0005, by Friedman's test) from a baseline value of 12.3 ± 1.4 µg/100 ml to a peak value of 21.0 ± 0.7 µg/100 ml 60 min after CRF and a risein mean plasma aldosterone levels from a basal value of 13 ± 2 ng/100 ml to a peak value of 23 ± 2 ng/100 ml. There was no significant difference between men and women in the responsiveness of ACTH, cortisol, and aldosterone to CRF administration. The individual basal cortisol levels were highly significantly and negatively correlated with the areas under the individual ACTH curves (r = −0.76; P < 0.005, by Pearson's correlation test) and cortisol curves (r = −0.91; P < 0.001, by Pearson's test). These data suggest a modulatory effect of physiological cortisol levels on the response of thepituitary-adrenal axis to CRF.