The activity of the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system in relation to waist/hip circumference ratio in men

Objective: To investigate possible differences, between generally and abdom inally obese men, in activity and regulation of the hypothalamic-pituitary- adrenal (HPA) axis and the sympathetic nervous system. Research Methods and Procedures: Fifty non-diabetic, middle-aged men were s elected to obtain two groups with similar body mass index (BMI) but differe nt waist/hip circumference ratio (WHR). Measurements were performed of the activity of the HPA axis and the sympathetic nervous system, as well as met abolic and endocrine variables. Results: Men with a high WHR, in comparisons with men with a low WHR, had h igher insulin, glucose, and triglyceride values in the basal state and high er glucose and insulin after an oral glucose tolerance test. Men with high WHR had elevated diurnal adrenocorticotropic hormone (ACTH) values but simi lar cortisol values, except lower cortisol values in the morning. Diurnal g rowth hormone concentrations showed reduced peak size. Stimulation of the H PA axis with corticotropin-releasing hormone (CRH) and laboratory stress sh owed no difference in ACTH values between groups, but cortisol values were lower in-men with high WHR. In comparison with men with a low WHR, men with a high WHR had elevated pulse pressure and heart rate in the basal state a nd after challenges by CRH and laboratory stress. They also had increased u rinary excretion of catecholamine metabolites. Discussion: These results suggest a mild dysregulation of the HPA axis, occ urring with elevated WHR independent of the BMI. The results also indicate a central activation of the sympathetic nervous system, such as in the earl y phases of hypertension, correlating with insulin resistance.