The hypothalamic-pituitary-adrenal axis in obese women with different patterns of body fat distribution

Abstract

To investigate whether obese subjects with abdominal obesity may be characterized by hyperactivity of the hypothalamic-pituitary-adrenal axis, we examined two groups of obese women with a waist to hip ratio (WHR) lower than 0.80 (n = 13), therefore having peripheral body fat distribution (P-BFD), or a WHR higher than 0.85 (n = 12), thus having abdominal body fat distribution (A-BFD). A group of seven normal weight healthy women served as controls. All subjects underwent the following protocol study that included 1) measurement of daily urinary free cortisol excretion rate; 2) a CRF test (human CRF, 1 microgram/kg BW, as iv bolus), with blood samples taken at regular intervals for ACTH and cortisol determination; and 3) an ACTH test, performed by administering two boli of ACTH (Synacthen, 0.2 microgram/kg BW, iv), at 90-min intervals, with blood samples taken for cortisol determination. Each woman also had a control saline study. Basal levels of both ACTH and cortisol rose significantly after CRF administration in all groups, but this increase was significantly higher in A-BFD than in P-BFD and control women. A significant correlation was found between the incremental area of cortisol and that of ACTH during the CRF test (r = 0.502), but not between these parameters and WHR values. Although the cortisol increase after the ACTH test was higher in A-BFD than in the other groups, these differences were only significant at 60 min during the test and when the analysis for repeated…