Adrenal Insufficiency, Relative
Basic Information 
Definition
Relative adrenal insufficiency (RAI) is a condition in which the adrenal gland, notably the adrenal cortex, is unable to respond (ie, secrete cortisol) to an appropriate level given the stimulus. RAI is often observed in patients with critical illness such as sepsis, in which adrenal hypofunction is considered part of the multiple organ dysfunction complex.
Species, Age, Sex
Premature foals have been shown to have hypofunctional hypothalamic-pituitary-adrenal axis (HPAA) responses, possibly due to underdevelopment; however, foals with sepsis or severe stress may have RAI, with a reported incidence of up to 52%.
Clinical Presentation
Etiology and Pathophysiology
• Prolonged or severe systemic illness leads to HPAA stimulation to yield increased cortisol concentrations.
• Diseases causing systemic inflammation and hypotension significantly increase HPAA responses.
• Excessive stimulation of the adrenal cortex (notably the zona fasciculata) results in an inability to secrete cortisol at an appropriate concentration for the stimulus (eg, adrenocorticotropin [ACTH])
• HPAA underdevelopment associated with neonatal prematurity may result in similar findings.
• In humans, subnormal cortisol responses have been associated with refractory hypotension and correlated with nonsurvival in certain patient populations (eg, septic shock).
Full access? Get Clinical Tree
