Stress Response and Endocrine Deregulation during Critical Illness

The stress system receives and integrates a diversity of cognitive, emotional, neurosensory, and peripheral somatic signals that arrive through distinct pathways. Activation of the stress system leads to behavioral and physical changes that are remarkably consistent in their qualitative presentation. The stress response is mediated largely by the hypothalamic-pituitary-adrenal (HPA) axis and the sympathoadrenal system, which includes the sympathetic nervous system and the adrenal medulla. The stress response is normally adaptive and time limited and improves the chances of the individual for survival. The time-limited nature of this process renders its accompanying antigrowth, antireproductive, catabolic, and immunosuppressive effects temporarily beneficial and/or of no adverse consequence to the individual. However, chronic activation of the stress system as occurs in critically ill patients may lead to a number of disorders, including stress hyperglycemia, dysfunction of the HPA and hypothalamic-pituitary-thyroid (HPT) axes, and hypothalamic-pituitary growth hormone (GH) dysfunction. These disorders are reviewed in this chapter. Diagnosis of adrenal insufficiency/critical illness