About cushing syndrome, true Is -: (A) Low dose dexamethasone suppress coisone secretion, (B) CA of adrenal is more common than adenoma, (C) Pituitary adenoma size > 2 cm (usually), (D) ACTH secretion is the commonest cause
Answer is D. most cases the cause is bilateral adrenal hyperplasia due to hyper secretion of pituitary ACTH or ectopic production of ACTH by a non pituitary source ( Harrison 17 pg 2255)