Abstract
The hypothalamic–pituitary–adrenal axis is essential for the adaptive response and for the maintenance of homeostasis during critical illness. Relative adrenocortical dysfunction as well as hypotension are often observed in septic shock and multiple organ dysfunction syndrome (MODS). This review highlights angiotensin II (Ang II), vasopressin (AVP) and apelin (APL) as ‘new’ factors that are potentially involved in the secretion of adrenocorticotrophic hormone (ACTH) and cortisol in critical illness. Indeed, Ang II is involved in all phases of the stress response, while exogenous infusion of AVP is generally effective at controlling intractable hypotension. Finally, APL can directly release ACTH and reduce plasma AVP. All of the proposed mechanisms by which these three neuropeptides could be involved in sepsis and MODS are discussed herein.