Low-dose overnight dexamethasone suppression test is used for diagnosing which condition?

Low-dose overnight dexamethasone suppression test is used for diagnosing which condition?

• A. Cushing disease
• B. Addison disease
• C. Adrenal carcinoma
• D. Hyperthyroidism

Answer: (A)

Low-dose overnight dexamethasone suppression testing is a screening tool for hypercortisolism, i.e., Cushing syndrome. In a normal person, a small dose of dexamethasone at night suppresses ACTH and lowers cortisol by the next morning. If cortisol remains elevated, it indicates Cushing syndrome rather than normal physiology. To determine the exact source of excess cortisol, further testing (like high-dose dexamethasone suppression or other workups) is used. Among the given options, the condition most aligned with this test is Cushing disease, a pituitary ACTH-secreting tumor that causes Cushing syndrome. Addison disease and hyperthyroidism aren’t diagnosed with this suppression pattern, and adrenal carcinoma can cause Cushing syndrome but the test primarily screens for the presence of hypercortisolism, with pituitary sources classically assessed via subsequent testing.

Low-dose overnight dexamethasone suppression testing is a screening tool for hypercortisolism, i.e., Cushing syndrome. In a normal person, a small dose of dexamethasone at night suppresses ACTH and lowers cortisol by the next morning. If cortisol remains elevated, it indicates Cushing syndrome rather than normal physiology. To determine the exact source of excess cortisol, further testing (like high-dose dexamethasone suppression or other workups) is used. Among the given options, the condition most aligned with this test is Cushing disease, a pituitary ACTH-secreting tumor that causes Cushing syndrome. Addison disease and hyperthyroidism aren’t diagnosed with this suppression pattern, and adrenal carcinoma can cause Cushing syndrome but the test primarily screens for the presence of hypercortisolism, with pituitary sources classically assessed via subsequent testing.