Two cases of Cushing's syndrome diagnosed by IPSS with normal or low plasma ACTH / 대한내과학회지

ABSTRACT

Cushing's syndrome results from prolonged exposure to high levels of glucocorticoid hormones. ACTH-dependent Cushing's syndrome accounts for about 85% of endogenous causes. Autonomous pituitary ACTH secretion, called Cushing's disease, is responsible for 80% of these causes, whereas ectopic ACTH secretion is responsible for 20% of them. Appropriate therapy of patients with Cushing's syndrome depends on accurate diagnosis and classification of the disorder. In addition to the history and clinical evaluation, the laboratory evaluation of a patient with Cushingoid appearance is necessary to establish the diagnosis and determine the cause of hypercortisolism. A major problem in the differential diagnosis of ACTH-dependent Cushing's syndrome is distinguishing Cushing's disease from the ectopic ACTH syndrome. Both entities can have similar clinical and laboratory features. In addition, both pituitary microadenoma and ectopic ACTH-secreting tumors may be radiologically occult. Bilateral inferior petrosal sinus and peripheral vein catheterization with simultaneous collection of samples for measurement of ACTH is one of the most specific tests available to localize the source of ACTH production. We report two cases of Cushing's syndrome diagnosed by inferior petrosal sinus sampling associated with normal or low ACTH levels on routine basal hormone assay.