Establishing Normal Ranges of Basal and ACTH-Stimulated Serum Free Cortisol in Children

摘要

Background: Normative data have been established for stimulated serum total cortisol in children but not for serum free cortisol. Methods: Children who were referred for ACTH testing to rule out adrenal insufficiency were enrolled. Only children with normal response and normal androgen levels were included. Total cortisol was determined by a chemiluminescence method, and free cortisol was measured by the same method following equilibrium dialysis. Results: The study group consisted of 85 subjects (28 male; 57 female) with a median age of 8.5 years (range 0.6-17.7). The mean basal and peak total cortisol levels were 11.5 +/- 5.7 and 32.9 +/- 6.2 mu g/dl, respectively. The mean basal and peak free cortisol levels were 0.4 +/- 0.3 and 1.8 +/- 0.6 mu g/dl, respectively. There was a negative correlation between peak total cortisol and age but not between peak free cortisol and age. The 3rd and 97th percentile values for peak free cortisol were 0.94 mu g/dl (26 nmol/l) and 2.97 mu g/dl (82 nmol/l), respectively. Conclusions: Measurement of free cortisol has the advantage of being independent of cortisol-binding globulin levels. This study provides reference ranges for stimulated free cortisol in children, with a cutoff value of 0.9 mu g/dl (25 nmol/l) as a normal response to a standard ACTH test. (C) 2016 S. Karger AG, Basel