Endocrine Abstracts (2008) 16 P510

Daily and nightly urinary free cortisol ratio as a marker of the hypothalamic-pituitary-adrenal (HPA) axis activity in abdominal obesity

Romina Di Agostinio1, Valentina Vicennati1, Uberto Pagotto1, Silvia Genghini1, Bruno Ambrosi2, Mauro Maccario2, Ettore Degli Uberti2, Marco Boscaro2, Francesco Cavagnini2, Franco Mantero2, Decio Armanini2, Roberto Vettor2, Mario Marugo2 & Renato Pasquali1

1Endocrinology Unit, Bologna, Italy; 2‘HPA axis and Obesity Group’, the Italian Society of Endocrinology, Bologna, Italy.

Abdominal obesity (AO) might have a hyperactivation of the HPA axis but previous studies are limited by the small and heterogeneous number of patients investigated. The aim of this study was to evaluate urinary free cortisol (UFC) output during daily and nightly hours in a large cohort of AO women versus normal weight controls (CT). 107 AO women and 37 CT women were enrolled in this study; all subjects underwent a complete physical examination, an OGTT and biochemical determinations. Moreover, each subject collected daily (from 0800 am to 0800 pm, dUFC) and nightly (from 0800 pm to 0800 am of the day after, nUFC) urine for UFC determinations.

Total cholesterol and triglycerides levels were significantly higher in the AO, whilst HDL were significantly lower than in CT. AO had significantly higher HOMA index than CT. There were no differences neither in dUFC nor in the nUFC between the groups but on the contrary, AO had significantly lower dUFC/nUFC ratio than CT. There was a negative and significant correlation between dUFC/nUFC and waist and BMI in all subjects. In the AO group, the correlation between dUFC/nUFC and anthropometric variables was still present, moreover, the ratio was also positively correlated to HOMA index.

In order to assess the linkage between HPA axis activity and metabolic syndrome, a multiple regression was performed in AO. dUFC/nUFC was still negatively and significantly correlated to BMI, while the correlation with waist circumference was lost. Interestingly, dUFC/nUFC was still positively and significantly correlated to HOMA index and systolic blood pressure. On the contrary, a negative and significant correlation was found between dUFC/nUFC and both HDL and diastolic blood pressure.

In conclusion, obesity by itself is characterized by high nightly UFC excretion. The HPA axis dysregulation is strictly associated to the abnormalities of the metabolic syndrome.