- strong evidence for Cushing s disease. This includes those with a central to peripheral ACTH gradient during IPSS or a lesion on pituitary MRI. We anticipate that these exclusion criteria will increase the ratio of patients with ectopic ACTH syndrome to those with Cushing s disease from the usual 1: 8 to 1: 2, thus we would accrue 3 patients to identify one with ectopic ACTH secretion.