Urinary free cortisol excretion pattern in morbid obese women

The urinary excretion of free cortisol in a group of 10 control and 20 morbidly obese women was measured in all bladder voidings during 24 h. The data from obese women were measured under Hospital basal controlled conditions and after 3 days of very low calorie diet (VLCD, 1.9 MJ/d). The hourly cortisol excretion pattern was determined for each woman, and means of each group were computed in order to obtain a 24 h excretion pattern. In controls, the highest excretion rate was in the morning (8-9 h) and the lowest at 21-22 h. Inbasal conditions, the obese showed a similar but flatter pattern; the highest peak was also in the morning (9-10 h), but the lowest rate was between 21 and 24 h. The VLCD diet flattened the pattern even more, in away that no clear peak was observed from the early morning until the afternoon; however, the nadir coincided with that found in basal conditions. These patterns resulted in significant differences between VLCD, basal diet and control. The amount of free cortisol excreted was 93.0 +/- 6.9 nmol/ day in controls, 70.1 +/- 4.7 nmol/day in obese under basal conditions and 62.6 +/- 3.0 nmol/day when subjected to VLCD. The results presented are consistent with a lower overall cortisol secretion in the morbid obese women, which also show a narrower margin of variation in cortisol secretion than non-obese controls. The data also show the significant influence of dietary energy on the pattern of cortisol excretion in obese women.