Majority of sick full term newborns have adequate adrenal cortical function in response to stress. Acutely ill neonates with a basal cortisol level less than 15 µg/dL (414 nmol/L) suggest adrenal insufficiency and require function testing of adrenal function. In premature infant, immaturity of hypothalamic-pituitary adrenal axis (HPA axis), may limit the ability to increase cortisol production in response to stress. The response to low dose ACTH and CRH appears to be useful as an additional test of adrenal function. CRH stimulation has been used increasingly in neonates. The ACTH and CRH stimulated cortisol response of more than 17 µg/dL (469 nmol/L) indicates a normal response.