Hypothalamic-Pituitary-Adrenal (HPA) axis functioning in relation to body fat distribution.

Summary Objective: to relate hypothalamo-pituitary-adrenal (HPA) axis functioning and HPA feedback functioning to body fat distribution in normal weight to obese subjects. Patients: 91 men and 103 women (age 18-45y, BMI 19-35 kg/m(2), waist-to-hip ratio (WHR) 0.6-1.1) Measurements: anthropometry, body composition using hydrodensitometry and deuterium dilution method, cortisol variability by measuring 5h cortisol concentrations, HPA axis feedback functioning using a dexamethasone suppression test, and HPA axis functioning under a challenged condition consisting of a standardized high intensity test with ingestion of 4 mg dexamethasone. Results: in men an inverse relationship was observed between 5h cortisol exposure (nmol/ml) and fat mass index (FMI) (kg/m(2)) (r=-0.55, p<0.001). In women relationships were observed between 5h cortisol exposure (nmol/ml.min) and WHR (r=-0.49, p<0.001), maximal workload (r=0.32, p<0.001) as well as oral contraceptive use (r=0.38, p<0.001). Similarly, in men an inverse relationship was observed between negative feedback expressed as baseline concentrations minus post dexamethasone cortisol concentrations (nmol/ml) and FMI (r=-0.53, p<0.001). In women relationships were observed between negative feedback expressed as baseline concentrations minus post dexamethasone cortisol concentrations (nmol/ml) and WHR (r=-0.43, p<0.001), maximal workload (r=0.30, p<0.001) as well as oral contraceptive use (r=0.43, p<0.001) in women. Moreover, an inverse relationship was observed between HPA axis functioning in a challenged condition expressed as percentage increase of cortisol concentrations after standardized high intensity test with ingestion of 4 mg dexamethasone (%) and waist (r=-0.21, p<0.10) in men and WHR (r=-0.21, p<0.05) in women. In male subjects, strong positive relationships were observed between FMI and waist circumference (r=0.85, p<0.001), as well as waist-to-hip ratio (r=0.70, p<0.001). Conclusion: disturbance of HPA axis functioning under basal and challenged conditions is related to visceral fat accumulation