ACTH-dependent Cushing syndrome

A form of endogenous Cushing syndrome (CS) caused by abnormal production of ACTH due, in 80% of cases, to adrenocorticotropic hormone (ACTH) oversecretion by a pituitary adenoma (Cushing disease, CD) and in 20% of cases to ectopic ACTH secretion (CS due to EAS) by an extrapituitary tumor (in 50% of cases originating in the lungs or less commonly in the thymus, pancreas, adrenal gland or thyroid) or very rarely due to a tumor secreting both ACTH and corticotrophin-releasing hormone (CRH).