The hypothalamic-pituitary-adrenal axis in critical illness.

Severe stress, associated with critical illness, activates the hypothalamic- pituitary-adrenal (HPA) axis and stimulates the release of cortisol from the adrenal cortex. Cortisol is essential for general adaptation to stress and plays a crucial role in cardiovascular, metabolic, and immunologic homeostasis. During critical illness, prolonged activation of the HPA axis can result in hypercortisolemia and hypocortisolemia; both can be detrimental to recovery from critical illness. Recognition of adrenal dysfunction in critically ill patients is difficult because a reliable history is not available and laboratory results are difficult to interpret. The review in this article will illustrate how adrenal dysfunction presents in critically ill patients and how appropriate diagnosis and management can be achieved in the critical care setting.