Which test is used in the initial hormonal workup to screen for cortisol excess in adrenal incidentaloma evaluation?

Which test is used in the initial hormonal workup to screen for cortisol excess in adrenal incidentaloma evaluation?

• A. Plasma metanephrines
• B. Overnight 1 mg dexamethasone suppression test
• C. Aldosterone/renin ratio
• D. CT scan of the adrenal glands

Answer: (B)

In evaluating an adrenal incidentaloma for cortisol excess, the first hormonal screen is the overnight dexamethasone suppression test. The principle is simple: in a normal system, a small amount of dexamethasone at night should suppress ACTH and lower morning cortisol. If cortisol remains high the next morning, it suggests autonomous cortisol production by the adrenal mass, indicating possible cortisol excess or subclinical Cushing’s syndrome. The standard protocol uses 1 mg of dexamethasone given at night, with cortisol measured the next morning. Suppression is typically defined as a morning cortisol below about 1.8 μg/dL (50 nmol/L); values above that raise concern for cortisol excess and warrant further confirmatory testing. Other listed tests target different adrenal issues: plasma metanephrines screen for pheochromocytoma, the aldosterone/renin ratio screens for primary aldosteronism, and a CT scan is imaging to visualize anatomy rather than assess hormone production.

In evaluating an adrenal incidentaloma for cortisol excess, the first hormonal screen is the overnight dexamethasone suppression test. The principle is simple: in a normal system, a small amount of dexamethasone at night should suppress ACTH and lower morning cortisol. If cortisol remains high the next morning, it suggests autonomous cortisol production by the adrenal mass, indicating possible cortisol excess or subclinical Cushing’s syndrome. The standard protocol uses 1 mg of dexamethasone given at night, with cortisol measured the next morning. Suppression is typically defined as a morning cortisol below about 1.8 μg/dL (50 nmol/L); values above that raise concern for cortisol excess and warrant further confirmatory testing.

Other listed tests target different adrenal issues: plasma metanephrines screen for pheochromocytoma, the aldosterone/renin ratio screens for primary aldosteronism, and a CT scan is imaging to visualize anatomy rather than assess hormone production.