The Endocrine Response to Critical Illness

The endocrine response to critical illness is composed of acute and chronic responses. The acute response is considered adaptive as a means of responding to physiologic stress. In this phase, stress stimulates the hypothalamic-pituitary-adrenal (HPA) axis, peripherally inactivates the hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-gonadal (HPG) axes, increases secretion of growth hormone, and induces insulin resistance and protein catabolism. The concept, diagnosis, and treatment of critical illness-related corticosteroid insufficiency remain controversial. The chronic response to critical illness is marked by central suppression of the HPT, HPG, and GH axes. This phase is particularly notable for continued protein catabolism and insulin resistance associated with significant morbidity and mortality.