Context: Topical corticosteroids are the recommended first-line treatment for all severities of persistent asthma and moderate to severe allergic rhinitis (AR). Potential adrenal suppression resulting from corticosteroid administration necessitates monitoring of children participating in clinical studies. Measurement of pretreatment cortisol concentrations is necessary to assess effects on adrenal function.

Objective: Plasma cortisol concentrations are assay dependent; normal reference range values must be obtained for each assay. Our objective is to provide these values for children as determined by high-performance liquid chromatography (HPLC).

Design and Patients: Two multicenter, randomized, double-blind, placebo-controlled studies evaluating basal and cosyntropin-stimulated morning plasma cortisol concentrations for patients aged 5 to <12 months with asthma and patients aged 2 to <6 years with AR using HPLC.

Main Outcome Measures: Main planned outcomes of these studies are reported elsewhere. This manuscript reports plasma cortisol concentration reference range values.

Results: In general, mean basal plasma cortisol concentrations (n = 177) (mean ± SD, nmol/L) were similar among the 5 to <9 month, 9 to <12 month, 2 to <3 year, 3 to <4 year, 4 to <5 year, and 5 to <6 year age groups (218 ± 149, 281 ± 144, 257 ± 105, 231 ± 83, 298 ± 118, and 237 ± 65, respectively) and increased to comparable levels 60 minutes after cosyntropin stimulation (n = 178) (622 ± 176, 638 ± 176, 697 ± 99, 655 ± 103, 662 ± 113, and 610 ± 68, respectively). However, patients <12 months had wider ranges of basal and stimulated values.

Conclusions: Basal and cosyntropin-stimulated morning plasma cortisol concentrations of children aged 5 to <12 months and 2 to <6 years were consistently measurable, with the large majority similar among the age groups examined, and comparable to those reported elsewhere for adults.