What is the Origin of Dexamethasone Suppression Test?

The development of the DST is fundamentally based on the established physiological principle of negative feedback within the HPA axis, where circulating glucocorticoids inhibit the release of ACTH from the pituitary gland. Researchers designed this test to exploit the potent suppressive effect of exogenous corticosteroids on the pituitary-adrenal axis. Various protocols, including the overnight and the low-dose/high-dose versions, were systematically refined to improve the test's sensitivity and specificity for various etiologies of cortisol excess.

What is the Mechanism of Dexamethasone Suppression Test?

Upon administration, the synthetic glucocorticoid dexamethasone binds to and activates glucocorticoid receptors in the pituitary gland. This receptor activation signals the pituitary to drastically reduce the secretion of Adrenocorticotropic Hormone (ACTH). In a healthy individual, this reduction in ACTH subsequently leads to a significant and measurable suppression of cortisol release from the adrenal cortex. A failure of the plasma or urinary cortisol level to suppress below a predetermined threshold following dexamethasone administration indicates a pathological, autonomous overproduction of cortisol.

Dexamethasone Suppression Test

Meaning

The Dexamethasone Suppression Test (DST) is a specialized diagnostic procedure in clinical endocrinology utilized to evaluate the integrity and regulation of the hypothalamic-pituitary-adrenal (HPA) axis. This test assesses the body’s negative feedback response to the administration of dexamethasone, a potent synthetic glucocorticoid. It serves as a primary screening tool for conditions of endogenous hypercortisolism, such as Cushing’s syndrome, by determining if the adrenal production of cortisol can be appropriately suppressed. The DST is critical for differentiating between normal physiological variation and pathological hormonal excess.