Leptin and the hypothalamic-pituitary-adrenal axis activity in women with different obesity phenotypes

OBJECTIVE: Women with visceral obesity may have hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis. Since glucocorticoids are involved in the expression of the ob gene, this study was carried out to investigate the relationship between serum leptin and the activity of the HPA axis in women with different obesity phenotypes. DESIGN: Cross sectional clinical study. SUBJECTS: Fifteen obese (Body Mass Index BMI28 kg/m(2)) women and ten normal weight control women (BMI26 kg/m(2)) were included in the study. MEASUREMENTS: Body fat distribution was defined by CT scan at the L4-L5 level. Baseline blood samples were obtained for hormone concentrations. The activity of the HPA axis was evaluated by measuring ACTH and cortisol blood levels after combined iv administration of corticotropin releasing factor (100 mu g) + arginine-vasopressin (0.3 IU). RESULTS: Baseline cortisol, ACTH, and androgen levels were similar in all groups, whereas leptin levels were significantly higher in the obese groups than in normal weight controls, without any significant difference between women with different obesity phenotypes. Incremental areas of ACTH and cortisol were significantly higher in women with visceral obesity than in those with subcutaneous obesity and controls. No significant correlation was found between the activity of the HPA axis and leptin concentrations. Leptin showed a highly significant correlation with BMI and subcutaneous fat and a weak but significant correlation with visceral fat and the visceral-to-subcutaneous fat ratio. CONCLUSION: Women with different obesity phenotypes had similar serum leptin concentrations but different HPA axis activity, and there was no correlation between them.