dexametasonisuppressio

Dexametasonisuppressio refers to the suppression of the body's natural production of cortisol by the adrenal glands, typically induced by exogenous administration of dexamethasone, a potent synthetic corticosteroid. This phenomenon is a key principle behind the dexamethasone suppression test, a diagnostic tool used to evaluate hypercortisolism, a condition characterized by excessive production of cortisol.

When a dose of dexamethasone is administered, it mimics the negative feedback mechanism of cortisol on the hypothalamic-pituitary-adrenal (HPA) axis. Normally, elevated cortisol levels signal the hypothalamus to reduce the release of corticotropin-releasing hormone (CRH) and the pituitary gland to reduce the release of adrenocorticotropic hormone (ACTH). This, in turn, suppresses cortisol production by the adrenal glands. Dexamethasone, being a synthetic glucocorticoid, binds to glucocorticoid receptors and exerts a similar suppressive effect.

In the standard low-dose dexamethasone suppression test, a small amount of dexamethasone is given orally, usually overnight. In healthy individuals, this exogenous dexamethasone will suppress the HPA axis, leading to significantly reduced levels of plasma ACTH and cortisol the following morning. Failure of cortisol levels to be adequately suppressed suggests a problem with the HPA axis, such as in Cushing's disease, where the pituitary gland autonomously produces excess ACTH, or in adrenal tumors that produce cortisol independently of ACTH stimulation. Higher doses of dexamethasone may be used in more complex testing to differentiate between the causes of hypercortisolism.