<prompt> A 40-year old man with central obesity, buffalo hump and veical purple striae on abdomen, has fasting blood glucose levels in high normal range. Plasma levels of ACTH and coisol are both increased compared to normal. An overnight high-dose dexamethasone test produces 75 suppression of coisol levels. This patient most likely hasAddisons diseaseAn ectopic ACTH-secreting tumorConns syndromeCushings disease  <response>: - Given patient has increased coisol ACTH levels with cushingoid signs symptoms. - This could result from either functional ACTH-secreting tumor in pituitary Cushings disease or an ectopic tumor such as a small cell carcinoma of lung, choice B. - To distinguish bw these two,high doses of potent synthetic glucocoicoiddexamethasone is administered High-dose dexamethasone suppresses ACTH secretion at least by 50 in Cushings disease Whereas secretion from ectopic tumor is not suppressed by dexamethasone. - As 75 suppression of coisol levels is seen in this pt, diagnosis is cushings disease. OTHER OPTIONS: Addisons disease choice A is primary adrenal insufficiency, with increased plasma ACTH producing hyperpigmentation decreased plasma coisol, aldosterone levels compared to normal. Conns syndrome choice C results from hypersecretion of aldosterone by adrenal coex resulting in decreased ACTH production. 