Value of urinary free cortisol/cortisone in assessing the activity of 11-beta-hydroxysteroid dehydrogenase in obese children: optimization of high performance liquid chromatography

ABSTRACT

Increased secretion of glucocorticoids is associated with obesity and cortisol secretion is increased in subjects with idiopathic obesity, especially of central distribution. Intercon-version of active cortisol with inactive cortisone is catalysed by the isozymes of 11 beta -HSD activities in different tissues can be assessed by ratio of urinary free cort isol to cortisone. The present study was carried out to evaluate the free cortisol/cortisone ratio in urine of obese children and adolescents to clarify the role of 11 beta-HSD in the pathogenesis of exogenous obesity. Thirty obese children were included in the present study; they were recruited from those attending Diabetic Endocrine Metabolic Pediatric Unit [DEMPU], Children Hospital, Cairo University, for assessment of obesity. Ten apparently healthy, non obese children matched in age and sex, were also included as controls. Urinary free cortisol [UFF] was measured by radio immune assay [RIA] and High performance liquid chromatography [HPLC] while urinary free cortisone [UFE] was measured by HPLC. The obtained results showed higher ratio of UFF/UFE in obese children suggesting that cortisol metabolism may be enhanced in children with higher body fat. This finding is supported by the positive correlation encountered between UFF and both BMI and fat%, which can be attributed to a higher activity of 11 beta-HSD-1 expressed in both subcutaneous and visceral fat with increased reactivation of cortisone to cortisol. This highlights the value of the UFF/UFE in demonstrating 11 beta-HSD activity more than measuring UFF or UFE alone. Finally, HPLC method under adopted conditions was found to be rapid, reliable and specific for measurement of both UFF and UFE