Adrenal axis in critical illness.

After a stressful event, adaptative mechanisms are carried out to support vital functions. Hypothalamic-pituitary-adrenal axis plays a key role in stress response regulating metabolism, cardiovascular function and immune system. This review addresses pathophysiological changes of the adrenal axis during critical illness, recognizing limitations of methods applied for its evaluation in this special context and defining indications for corticosteroid replacement in critically ill patients. The concept of relative adrenal insufficiency should be abandoned; cosyntropin stimulation test should not be performed for diagnosis of adrenal insufficiency in critical illness nor for establishing the need of treatment.