Background: Excess endogenous or exogenous cortisol is a potent stimulus for fat gain.
Objective: We examined whether physiologic variations in endogenous cortisol secretion may be associated with changes in body composition during growth.
Design: Anthropometric measurements and 24-h excretion rates of urinary free cortisol (UFF) and cortisone (UFE) and the sum of 3 major glucocorticoid metabolites (GC), which reflects overall daily cortisol secretion, were determined cross-sectionally in healthy preschool (50 boys and 50 girls aged 4-5 y), late prepubertal (50 boys and 50 girls aged 8-9 y), and pubertal (50 males aged 13-14 y and 50 females aged 12-13 y) subjects.
Results: Significant positive associations (P < 0.001) were found between GC excretion and fat mass, percentage body fat, and body mass index by using covariance analysis adjusted for the grouping factors sex and age. The relations between GC and indexes of body fat remained significant (P < 0.05) even after GC was corrected for individual body surface area and the effect of maternal body mass index on fatness was considered. No consistent associations with fat indexes were seen for UFF, UFE, or the ratio of major urinary cortisol to cortisone metabolites, which reflects 11 beta-hydroxysteroid dehydrogenase type 1 activity.
Conclusions: Although direct effects of UFF and UFE on body composition were not shown, our findings strongly suggest that a higher adrenocortical activity is one endocrine-metabolic feature of healthy children with higher body fat. Whether urinary GC is a long-term predictor of fat gain during childhood should be analyzed in future studies.