Objective: Morning cortisol levels are frequently used as screening tests for adrenal insufficiency in both adults and children. Reports differ on the specificity of this measurement. The present study was undertaken to determine whether sex or pubertal status affected morning cortisol values.
Methods: We measured morning cortisol levels and performed low-dose adrenocorticotropic hormone stimulation test in 35 healthy male and female subjects (ages 6-34) ranging in Tanner stage (TS) from TS 1 to TS 5. Testing was initiated at 08:00 after an overnight fast. Morning serum total cortisol, free cortisol, cortisol-binding globulin, estradiol (males and females), and testosterone (males) were obtained.
Results: Morning total and free cortisol levels were significantly higher in TS 5 participants than in prepubertal children. Using a morning cortisol of 248 nmol/L to define a normal value, 19/21(90%) of healthy TS 5 subjects exhibit normal values. In contrast, 0/8 TS 1 healthy subjects exhibited a value greater than 248 nmol/L (p=0.0005). We also observed sex differences in morning cortisol levels in pubertal but not in prepubertal subjects. We observed sex differences in morning cortisol levels in TS 5 individuals.
Conclusions: Morning cortisol measurements may be more useful as screening tests for adrenal function in adults than in children. TS and sex may be considered in the decision to screen for adrenal insufficiency using morning cortisol or whether to proceed directly to stimulation testing.