Corticotropin Releasing Hormone Stimulation Test and Nocturnal Cortisol Levels in Normal Children

ABSTRACT: This study examined hypothalamic-pituitary-adrenal axis functioning in a group (n = 25) of very carefully screened normal children with considerable attention to issues of adaptation and procedural stress. The subjects (mean age 10.3 ± 1.6 y) were selected as “supernormal” controls as a part of a large psychobiologic study of childhood depression. After careful acclimatization over 24 h, the subjects underwent all-night sampling of plasma cortisol every 20 min, then the following evening had a corticotropin releasing hormone (CRH) stimulation test (using human CRH). Human CRH resulted in a rapid stimulation of adrenocorticotropin and cortisol. Adrenocorticotropin levels increased from 6.8 ± 3.5 (± SD) pmoI/L (30.7 ± 16.1 pg/dL) to a peak of 11.6 ± 5.5 pmol/L (52.9 ± 24.8 pg/mL) at 15 min with return to baseline levels by 60 min. Cortisol levels increased from 131.4 ± 59.7 nmol/ L (4.8 ± 2.2 Mg/dL) to a peak of 427.0 ± 113.5 nmol/L (15.5 ± 4.1 Mg/dL) at 30 min with return to baseline by 120 min. The cortisol peak was significantly greater (p < 0.05) in boys [474.6 ± 129.7 nmol/L (17.2 ± 4.7 ng/dL)] than in girls [366.9 ± 52.4 nmol/L (13.3 ± 1.9 ng/dL, p < 0.05)]. Age, body mass index, and pubertal status were not significantly related to hypothalmic-pituitary-adrenal axis measures. Nocturnal cortisol reached a nadir at 160 ± 60 min after sleep onset (0102 h) and a peak 480 ± 60 min after sleep onset (0612 h). Nocturnal cortisol levels were significantly (positively) correlated with human CRH-stimulated cortisol (r = 0.56, p = 0.004). There was also significant correlation between sleep continuity and nocturnal cortisol (Spearman rho = −0.55, p = 0.005) and between sleep continuity and human CRH-stimulated cortisol (Spearman rho = −0.53, p = 0.008). These significant correlations across different stress measures indicate the importance of individual (subject) differences in patterns of stress response. These results also highlight the need to consider procedural, subjective, and psychologic factors when conducting tests measuring stress hormone levels in children.