Assessment of hair cortisol as a potential biomarker for possible adrenal suppression due to inhaled corticosteroid use in children with asthma: A retrospective observational study

Background: Inhaled corticosteroids (ICS) are the recommended long-term control therapy for asthma in children. However, concern exists regarding potential adrenal suppression with chronic ICS use. Our pilot study reported that hair cortisol in children was 50% lower during ICS therapy than prior to therapy, suggestive of adrenal suppression. Objective: To evaluate hair cortisol concentration (HCC) as a potential biomarker for possible adrenal suppression from ICS use in children with asthma. Methods: A retrospective observational study was performed at asthma clinics in Vancouver, Winnipeg, and Toronto, Canada. Children (n = 586) were recruited from July 2012 to December 2014 inclusive of those without asthma, with asthma not using ICS, and with asthma using ICS. The most recent three-month HCC was measured by enzyme immunoassay and compared among the groups. Quantile regression analysis was performed to identify factors potentially affecting HCC. Results: The median HCC was not significantly different among the children: No ICS (n = 47, 6.7 ng/g, interquartile range (IQR) 3.7–9.8 ng/g), ICS Treated (n = 360, 6.5 ng/g, IQR 3.8–14.3 ng/g), and Controls (n = 53, 5.8 ng/g, IQR 4.6–16.7 ng/g). 5.6% of the children using ICS had hair cortisol <2.0 ng/g compared to none in the control groups (P <.05, comparing ICS Treated (20/360) to all Controls combined (0/100)) and only half had been exposed to systemic corticosteroids. Age, sex, BMI, and intranasal corticosteroid use were significantly associated with HCC. Conclusions: Results suggest HCC may be a potential biomarker for adrenal suppression as a population of children using ICS with HCC < 2.0 ng/g was identified compared to none in the control groups. Further research is needed to determine if those children have or are at risk of adrenal suppression or insufficiency.