title: New insights into the controversy of adrenal function during critical illness.
abstract: Critical illness represents a life-threatening disorder necessitating recruitment of defence mechanisms for survival. Herein, the hypothalamic-pituitary-adrenal axis is essential. However, the relevance of a relative insufficiency of the hypothalamic-pituitary-adrenal axis in critical illness, which is diagnosed by a suppressed cortisol response to exogenous adrenocorticotropic hormone (ACTH) irrespective of the plasma cortisol concentration, is controversial. Findings from several studies have provided insights that clarify at least part of this controversy. Rather than an activated hypothalamic-pituitary-adrenal axis, ACTH-independent regulators have been reported to contribute to increased cortisol availability during critical illness. One of these regulators is reduced cortisol breakdown, mediated by suppressed expression and activity of cortisol metabolising enzymes in the liver and kidneys. This downstream mechanism increases concentrations of plasma cortisol, but the ensuing feedback-inhibited ACTH release, when sustained for more than 1 week, has been shown to negatively affect adrenocortical integrity and function. Reduced adrenocortical ACTH signalling could explain reduced cortisol responses to exogenous ACTH. Whether such reduced cortisol responses in the presence of raised plasma (free) cortisol identifies adrenal failure needing treatment is unlikely. Additionally, reduced cortisol breakdown affects the optimum dose of hydrocortisone treatment during critical illness. Identification of patients with an insufficient hypothalamic-pituitary-adrenal axis response and the optimum treatment for this disorder clearly need more well designed preclinical and clinical studies.
authors.affiliation: Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, KU Leuven University, Leuven, Belgium.
authors.forename: Eva
authors.initials: E
authors.lastname: Boonen
authors.affiliation: Department of Medicine III, Universitätsklinikum Carl Gustav Carus an der Technischen Universität Dresden, Dresden, Germany; Diabetes and Nutritional Sciences, Rayne Institute, Denmark Hill Campus, King's College London, London, UK.
authors.forename: Stefan R
authors.initials: SR
authors.lastname: Bornstein
authors.affiliation: Clinical Division and Laboratory of Intensive Care Medicine, Department of Cellular and Molecular Medicine, KU Leuven University, Leuven, Belgium. Electronic address: greet.vandenberghe@med.kuleuven.be.
authors.forename: Greet
authors.initials: G
authors.lastname: Van den Berghe
mesh_terms: D000302:Adrenal Cortex / Q000378:metabolism*; D000311:Adrenal Glands / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D016638:Critical Illness / Q000628:therapy; D025461:Feedback, Physiological; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism* / Q000627:therapeutic use; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000378:metabolism*
chemical_list: D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone