[ACTH-dependent Cushing syndrome, a diagnostic challenge].

ACTH dependent Cushing syndrome accounts for approximately 80% of all Cushing syndrome. Distinguishing the pituitary origin from ectopic one is still a diagnosis problem in some cases, especially in bronchial carcinoids, because approximately 50% show cortisol suppresion after dexametasone and may be small and, therefore, difficult to detect in chest radiography. We present a case of a patient with ACTH dependent Cushing syndrome of difficult localization with usual diagnosis tests.