Hair cortisol concentrations exhibit a positive association with salivary cortisol profiles and are increased in obese prepubertal girls

Cortisol, a key mediator of the stress response, has been associated with obesity and metabolic syndrome manifestations as early as in childhood. Scalp hair cortisol has been proposed as a reliable index of long-term circulating cortisol. We aimed to investigate whether obese prepubertal girls have higher scalp hair cortisol than normal-weight controls and whether hair cortisol levels are correlated with salivary cortisol concentrations in these groups. In this cross-sectional study, 25 obese girls and 25 normal-weighted, age-matched girls were enrolled. Anthropometric evaluation, blood chemistry and salivary cortisol measurements were performed, and body mass index (BMI) and areas under the curve with respect to ground (AUCg) were calculated. Hair cortisol determination was performed with liquid chromatography-tandem mass spectrometry. Both hair cortisol concentrations and salivary cortisol AUCs were higher in the obese than the normal-weight girls (p < .001 and p = .002, respectively). A positive correlation between hair cortisol and BMI Z-score was found (rho = .327, p = .025), while hair cortisol correlated positively with salivary cortisol AUCg (rho = .3, p = .048). We conclude that obese prepubertal girls have higher hair and salivary cortisol concentrations than their age-matched lean counterparts. Hair cortisol assessment seems to be a sensitive method of evaluating systemic cortisol exposure, which is supported by our finding that hair cortisol is associated with salivary concentrations of the hormone. Lay Summary: Cortisol is the key hormone of the stress response. Childhood obesity has been associated with cortisol production dysregulation. Our findings suggest a positive association between obesity in prepubertal girls and elevated cortisol concentrations, measured in saliva and hair.