<prompt> In a chronic smoker with mild haemoptysis. He also gave a history of hypertension and obesity. Lab data showed raised ACTH levels, which were not suppressed by dexamethasone. The cause for the Cushings syndrome in the patient is -MEN IPituitary adenomaAdrenal cortical adenomaEctopic ACTH secreting tumor  <response>: Remember thisIn normal person Low dose dexamethasone suppresses cortisol secretion. In Cushings syndromes Low dose dexamethasone is unable to suppress cortisol secretion.When Cushings syndrome is caused due to ectopic ACTH production Even high dose dexamethasone is unable to suppress cortisol secretion. 