Endocrine Abstracts

Introduction: Obesity in children is rising worldwide with premature development which could involve greater risk of complications and comorbidities in adult life. Central adiposity is a well known feature of glucocorticoid excess and there are some speculations that cortisol biosynthesis is involved in pathogenesis of metabolic syndrome. However the circadian rhythm of cortisol axis or incrimination of cortisol excess in obese children is less known. Our aim is to investigate diurnal cortisol levels and other hormonal tests in relation to body composition in obese children.

Patients and method: Twenty three overweight and obese children (12 boys, 11 girls) were included in this study with ages 7–17 years. Height, weight and pubertal stage were recorded. Basal cortisol was taken at 8 a.m. as well as TSH, FT4, and ACTH. To determine skeletal maturation, hand radiography was performed. Body composition (BC) was measured using dual – energy x-ray absorptiometry (Hologic Delphi A: version 12.6.2). Whole body and regional body composition including fat mass and lean body mass were measured after an overnight fast, with participants in the supine position.

Results: Eighteen (78.2%) children were obese (> 95^th percentile): 11 boys and 7 girls. Five (21.73%) children were overweight (85–95^th percentile): 4 girls and 1 boy. Of overall participants, 18 children (10 girls and 8 boys) had DXA total body fat above 40%. TSH result was elevated (> 5.5 uIU/mL) in 3 girls (13%) and moderate elevated (>4 uIU/mL) in 3 girls and 1 boy meaning 20% of participants. Diurnal cortisol was low (<5 μg/dL) in 2 boys and 1 girl (13%) and moderate low (<10 μg/dL) in 6 boys and 4 girls meaning 50% of children. Bone age exceeded chronological age by minimum 2 years in 6 of 9 children.

Conclusion: Overweight and obese children had low morning cortisol, this findings are in accordance with previous studies. One hypothesis is that obesity enhances cortisol clearance resulting low morning cortisol compensated by higher evening secretion. Also stress is suggested to play an important role in development of children obesity, so reducing direct emotional stress may be a critical prevention strategy. The mechanism of elevated TSH and obesity is not known, insulin resistance and leptin may be involved. Also, obesity is linked to advanced pubertal evolution that explains bone age maturation in our participants, most likely due to altered steroid hormones synthesis attributed to obesity.