POMC and ACTH Syndrome, Ectopic: Numerous biochemical tests have been evaluated to establish the diagnosis of CS and to differentiate the etiology which can be categorized into adrenocorticotropin (ACTH)-dependent CS caused by pituitary (Cushing disease [CD]), or ectopic tumors (ectopic ACTH syndrome [EAS]), or ACTH-independent (adrenal Cushing's [AC]).