This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
[{'content': "Which of the following statements about Cushing's disease is true? \nSelect and explain. \nA. Serum adrenocoicotropin (ACTH) levels usually are low, B. Pituitary microadenoma usually is present, C. There is a high incidence of nonendocrine tumors, D. Nonsuppression of coisol 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 coisol production, regardless of aetiology.Cushing's disease usually is caused by a pituitary microadenoma producing high adrenocoicotropin (ACTH) levels.In most patients, coisol 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 centres.", 'role': 'assistant'}]