What is the recommended test for monitoring an incidental adrenal mass?

The overnight dexamethasone suppression test is the recommended test for monitoring an incidental adrenal mass primarily to assess for hypercortisolism, which can be associated with adrenal tumors such as adrenal adenomas or carcinomas. This test helps determine how well the body regulates cortisol production in response to dexamethasone, a synthetic glucocorticoid.

If the suppression of cortisol levels occurs after administration of dexamethasone, it is suggestive of a normal adrenal function, whereas failure to suppress cortisol output might indicate conditions such as Cushing's syndrome, which could be related to the adrenal mass. Therefore, this test is crucial in stratifying the risk associated with the adrenal mass and deciding on further management.

Other methodologies, such as imaging or urine cortisol tests, serve different purposes. A 24-hour urine free cortisol test is useful in confirming the diagnosis of excess cortisol production but is not specifically designed for initial monitoring of incidental adrenal masses. A computed tomography (CT) scan provides imaging information but does not give functional status, while magnetic resonance imaging (MRI) is also used for imaging purposes and, similar to CT, doesn't evaluate hormone production. Hence, the dexamethasone suppression test is vital for functional assessment,