Morning Serum Basal Cortisol Levels Are Affected by Age and Pubertal Maturation in School-Aged Children and Adolescents

Abstract

Background: The same reference values for cortisol have been used for adults and children, but laboratory results obtained from an adult population might not be suitable for pediatric patients. Aims: To determine morning serum basal cortisol levels in children and adolescents. Methods: The study was conducted on 120 suitable reference individuals, healthy Brazilian children and adolescents from both genders aged 4-19 years old. The method used for cortisol assessment was the chemiluminescent enzyme immunoassay (VITROS® 5600 MicroWell; Johnson & Johnson, High Wycombe, UK, 2009), and the kit reference interval was 4.46-22.7 μg/dl (122.7-626.2 nmol/l). The setting limits were calculated according to the Clinical Laboratory Standards Institute guidelines. Results: The morning serum basal cortisol levels increased with age and pubertal maturation, but there were no differences based on gender. The cortisol reference values were established based on the 2.5th and 97.5th percentiles as 2.97 μg/dl [81.9 nmol/l, 90% confidence interval (CI) 1.44-3.69 μg/dl] and 23.4 μg/dl (645.5 nmol/l; 90% CI 16.3-26.4 μg/dl), respectively. Conclusions: The assessment of the morning serum basal cortisol levels showed a unique pattern, with a different lower limit for the cohort compared to current values established for adult subjects.