SEX-DEPENDENT ALTERATION IN CORTISOL RESPONSE TO ENDOGENOUS ADRENOCORTICOTROPIN

We have investigated ACTH and cortisol secretion patterns in two groups of five healthy adult male and female subjects. Plasma samples were obtained at 10-min intervals for 24 h, and pulsatile hormone release was analyzed by a multiparameter deconvolution technique. ACTH secretion was greater in male than female subjects; the production rate per 24 h was 139 +/- 7 pmol/L distribution volume in males, and 89 +/- 11 pmol/L distribution volume in females (P = 0.007). Cortisol secretion did not differ significantly between sexes; in males, the 24-h secretion rate was 2807 +/- 239 nmol/L distribution volume, and in females, it was 2970 +/- 411 nmol/L distribution volume (P = NS). The number of ACTH secretory pulses per 24 h, as determined by deconvolution analysis, was 16.2 +/- 1.4 in males and 19.6 +/- 2.0 in females (P = NS). There were no sex differences in the number of cortisol pulses or the calculated half-lives of ACTH and cortisol. ACTH and cortisol pulses were significantly concordant at a cortisol lag time of 10 min, as demonstrated by probability analysis and cross-correlation with autoregressive modeling. Based on a significantly different regression intercept of cortisol pulse height on ACTH pulse height in women than in men (P < 0.001) and a higher ratio of cortisol to ACTH production rates in women than in men (P = 0.013), we suggest that the female adrenal cortex is more responsive to ACTH than its male counterpart in terms of glucocorticoid production. Consequently, equivalent daily cortisol secretion rates are attained in men and women at the expense of greater ACTH release in men.