Clinical Information

The primary use of this test is to ensure that dexamethasone concentrations are adequate for interpretation of cortisol concentrations following the overnight dexamethasone administration. Suboptimal dexamethasone concentrations may be seen when absorption of dexamethasone is impaired, when metabolism of dexamethasone is accelerated due to concomitant medications, or when instructions for taking or timing of dexamethasone are not followed.

Overnight dexamethasone suppression testing is a standard-of-care endocrine test for assessment of mild autonomous cortisol secretion in adrenal tumors or for evaluation of endogenous hypercortisolism (Cushing syndrome) of any kind (ectopic, pituitary, adrenal). Consensus guidelines recommend concomitant measurement of dexamethasone and cortisol to minimize the risk of false-positive results when performing dexamethasone suppression testing.(1)

An additional potential application of this test is to aid in the assessment of secondary adrenal insufficiency.

Synthetic glucocorticoids are widely used and have an important clinical utility both as anti-inflammatory and immunosuppressive agents. The medical use of these agents, as well as their surreptitious use, can sometimes lead to a confusing clinical presentation. Patients exposed to these steroids may present with clinical features of Cushing syndrome but with suppressed cortisol and corticotropin concentrations, ie, hypothalamus-pituitary-adrenal axis suppression. This test provides measurements of dexamethasone, a commonly used glucocorticoid. The synthetic glucocorticoid screen measures a broader spectrum of synthetic glucocorticoids and would be the recommended test when exogenous glucocorticoid exposure is suspected; see SGSS / Synthetic Glucocorticoid Screen, Serum.