This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
[{'content': 'Which of the following statements about Cushing’s disease is true? \nSelect and explain. \nA. Serum adrenocorticotropin (ACTH) levels usually are low, B. Pituitary microadenoma usually is present, C. There is a high incidence of nonendocrine tumors, D. Nonsuppression of cortisol production by the high-dose dexamethasone suppression test is a characteristic finding', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Cushing’s syndrome is due to increased adrenal cortisol production, regardless of etiology.\nCushing’s disease usually is caused by a pituitary microadenoma producing high adrenocorticotropin (ACTH) levels.\nIn most patients, cortisol levels would be suppressed as a result of the high-dose dexamethasone suppression test.\nTranssphenoidal microsurgical removal of the microadenoma is the treatment of choice in most centers.', 'role': 'assistant'}]