Low-dose adrenocorticotropic hormone stimulation testing in term infants

Background: Low-dose adrenocorticotropic hormone (ACTH) stimulation testing is a commonly accepted way to evaluate adrenal function in children. However, there are no published data on the use of this test in term infants less than 12 months of age outside the newborn period. Methods: We identified 14 infants at our center who were full term and had one or more ACTH tests at less than 12 months of age to evaluate for secondary adrenal insufficiency (AI). We retrospectively assessed peak cortisol response in these infants to determine whether a cut-off of 20 μg/dl is appropriate to distinguish normal from abnormal adrenal function in this age group. Results: Five infants had peak cortisol ≥20 μg/dl on their first ACTH test and had a clinical picture consistent with normal adrenal function. Nine infants had peak cortisol <20 μg/dl on their first ACTH test. When retested later in infancy, four of these patients achieved peak cortisol ≥20 μg/dl. Conclusions: In term infants, the low-dose ACTH stimulation test is useful for demonstrating normal adrenal function but is of limited value in diagnosing secondary AI. For infants with peak cortisol <20 μg/ dl, clinical observation and repeat ACTH testing later in infancy clarified diagnosis.