LAUSR

Background: The utility of circadian cortisol variation in estimating the degree of hypercortisolemia in different forms of endogenous Cushing syndrome (CS) has not been evaluated in children yet. Methods: A retrospective cohort study, including children who underwent surgery due to CS (n = 115), was divided into children with a pituitary adenoma (Cushing disease) (n = 88), primary adrenal CS (n = 21), or ectopic adrenocorticotropin- or corticotropin-releasing hormone (ACTH-/CRH)-secreting tumors (n = 6). Circadian plasma cortisol measurements were obtained at 11: 30 p.m. and at midnight, and at 7: 30 and 8: 00 a.m. The ratios between the morning and late-night concentrations were calculated. Results: Plasma cortisol early-morning and midnight (AM/PM) ratios negatively correlated with 24-h urinary free cortisol (UFC) collections among the full study population and in each of the individual etiologies. Plasma ACTH concentrations positively correlated with plasma cortisol AM/PM ratios among patients with ACTH-independent CS. Finally, patients with primary pigmented nodular adrenocortical disease showed no correlation between UFC collections and the plasma cortisol AM/PM ratio, in contrast with other etiologies for primary adrenal CS, which showed a strong negative correlation between them. Conclusion: Our study shows the association between the plasma cortisol AM/PM ratio and the degree of hypercortisolemia in children with CS.