About cushing syndrome, true Is -
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)
Low dose dexamethasone suppress coisone secretion
CA of adrenal is more common than adenoma
Pituitary adenoma size > 2 cm (usually)
ACTH secretion is the commonest cause
Endocrinology