<prompt> Which of the following statements about Cushings disease is true?Serum adrenocorticotropin ACTH levels usually are lowPituitary microadenoma usually is presentThere is a high incidence of nonendocrine tumorsNonsuppression of cortisol production by the high-dose dexamethasone suppression test is a characteristic finding  <response>: Cushings syndrome is due to increased adrenal cortisol production, regardless of etiology.Cushings disease usually is caused by a pituitary microadenoma producing high adrenocorticotropin ACTH levels.In most patients, cortisol levels would be suppressed as a result of the high-dose dexamethasone suppression test.Transsphenoidal microsurgical removal of the microadenoma is the treatment of choice in most centers. 