Relative Adrenal Insufficiency (RAI): Unrecognized in Neonates with Cyanotic Congenital Heart Disease

Introduction At any age, functional hypothalamic-pituitary-adrenocortical (HPA) axis is essential for the maintenance of homeostasis during physiologic and stressful (illness) states [1-4]. Though the mechanisms of elevated serum cortisol in maintaining body milieu under these conditions remain unclear, even relative cortisol insufficiency leads to hypoglycemia, hypotension, shock and even death [1-8]. Relative adrenal insufficiency (RAI) occurs when serum cortisol concentration does not increase appropriately in response to stress or illness [1-10]. The definition of RAI in ill adults is a random serum cortisol of <15 μg/dl or an increase of less than 9 μg/dl in response to exogenous ACTH stimulation [26]. The incidence of RAI varies from 5 to 50% in adults, children and neonates with other critical illnesses [2-8].