What does a positive low-dose dexamethasone suppression test indicate?

A positive low-dose dexamethasone suppression test indicates that the body's cortisol production is not being adequately suppressed by dexamethasone, which is a glucocorticoid. This lack of suppression suggests the presence of Cushing's syndrome, a condition characterized by excessive levels of cortisol in the body, which can be due to various causes such as adrenal tumors, pituitary adenomas, or ectopic ACTH production. In a healthy individual, administration of dexamethasone typically suppresses cortisol production; therefore, a positive test suggests that the feedback mechanism is impaired, which is a hallmark of Cushing's syndrome.

Understanding this concept is important for diagnosing conditions related to abnormal cortisol levels, guiding further diagnostic testing and management of the patient.