Adrenal Function in Critical Illness

An appropriate hypothalamic-pituitary-adrenal (HPA) axis response is required to survive critical illness. Primary adrenal insufficiency, relative adrenal insufficiency, tissue resistance to glucocorticoids, ACTH deficiency and immune-mediated inhibition of the HPA axis may impair the secretion or action of glucocorticoids in critically ill patients. Adrenal insufficiency is estimated to occur in up to 77 percent of critically ill patients, but currently, there is no consensus on the diagnostic criteria for adrenal insufficiency in this setting, and standard testing does not discriminate among the aforementioned factors. We will study the incidence and natural history of adrenal insufficiency in critically ill patients to further define adrenal insufficiency and provide data to develop diagnostic tests. Clinical features and outcomes will be correlated with laboratory measurements of hormones, cytokines and glucocorticoid action. Healthy volunteers will undergo cortrosyn tests with measurement of free cortisol levels to develop a normative range for this endpoint. Patients with known adrenal insufficiency will also be studied to help determine the clinical utility of diagnostic tests among these different groups. Previous glucocorticoid use, if prolonged and supraphysiologic, also inhibits the HPA axis and can result in adrenal insufficiency. Patients with short intermittent courses of glucocorticoid administration have not been studied well, and may also be at risk. To gain further information about this group, patients receiving pulse glucocorticoid doses as part of bone marrow transplant regimens at the Clinical Center will also be studied.