Elevated serum cortisol and elevated ACTH. ( Normally should be suppressed) To differentiate if ACTH coming from pituitary or ectopic do an overnight dexamethasone suppression test with 8 mg. If level of ACTH is suppressed to less than 1/2 or normal diagnostic of Cushing Disease. Next is to image brain with MRI. To r/o ectopic ACTH form malignancy check 17 hydroxysteroid. Elevated