Copeptin in obese children and adolescents: relationships to body mass index, cortisol and gender.

OBJECTIVE: Copeptin has been reported to be associated with stress, obesity and the metabolic syndrome (MetS) in adults. However, data in childhood are scarce. Therefore, we studied the relationships between copeptin, cortisol, puberty and parameters of the MetS in children.

DESIGN: Cross-sectional study.

PATIENTS: A total of 51 obese children (10·8 ± 3·2 years, 39% male, 45% prepubertal, body mass index standard deviation score (BMI-SDS) 2·77 ± 0·56) and 24 lean children of similar age, gender and pubertal stage.

MEASUREMENTS: Copeptin, serum cortisol, 24-h urinary free cortisol, BMI-SDS and, as parameters of the MetS, insulin resistance index (HOMA), HbA1c, uric acids, blood pressure and lipids.

RESULTS: Copeptin levels were significantly (P = 0·047) higher in obese children (5·8 ± 2·8pmol/l) compared to lean children (4·6 ± 2·2pmol/l). BMI-SDS (β-coefficient 0·38 ± 0·35, P =0·033), but not any parameter of the MetS, was significantly related to copeptin in multiple linear regression analyses adjusted for age, gender and pubertal stage. A 24-h urinary free cortisol (β-coefficient 0·13 ± 0·06, P < 0·001), but not serum cortisol, was significantly related to copeptin in multiple linear regression analyses adjusted for age, gender, pubertal stage and BMI-SDS. Pubertal boys (6·6 ± 2·8pmol/l) demonstrated significantly (P = 0·042) higher copeptin levels compared to pubertal girls (4·8 ± 2·6pmol/l), while copeptin concentrations did not differ between prepubertal girls and boys.

CONCLUSIONS: Copeptin levels are related to 24-h urinary free cortisol in obese children. Pubertal boys, but not prepubertal boys, demonstrated higher copeptin levels than girls, suggesting that sex hormones are involved in the regulation of copeptin levels. Further studies are necessary to understand the relationship between obesity, cortisol, gender, pubertal stage and copeptin levels.