Plasma Cortisol Levels Increase with Age in Obese Subjects

Abstract

In order to assess the influence of age, sex, and body mass on plasma cortisol concentrations, we measured the 24‐hour Integrated Concentration (IC) of cortisol (F) in 36 obese subjects (16 males, 20 females) aged 5.3–56.4 years, BMI=35.5 ± 7.3 kg/m2 and compared with 119 nonobese subjects, body mass indices (BMI) 21.2 ± 2.7 kg/m2, aged 8.8–66.2 years (55 males, 64 females). Subjects were nondiabetic, normotensive, without history of psychiatric illness, and otherwise in good health. IC studies were performed using a continuous blood withdrawal methodology, and IC‐F was assayed from the 24 hour pooled sample by a protein binding method. The effect of age and gender on IC‐F was analyzed by multivariate regression. In the nonobese group there was no effect of age or sex on IC‐cortisol levels, the mean IC‐F= 173.8 ± 44.1 nmol/L. A statistically significant but weak negative effect of BMI on IC‐cortisol (r = ‐.18, p<0.05) was present. In the obese subjects there was a significant increase in IC‐cortisol levels with age IC‐F(nmol/L)=2.76 x age(years) + 85.0 (r2=.36, p<0.0001). IC‐cortisol levels tended to be lower in obese males than females when controlled for age (p<0.05). We conclude that in nonobese subjects IC‐F levels are independent of age and gender. However, there is a significant increase of IC‐cortisol levels with age in obese individuals. The observed increase of IC‐cortisol with age may contribute to metabolic complications of obesity. 1993 North American Association for the Study of Obesity (NAASO)