This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cushing Syndrome, Subject name: Medicine
[{'content': 'A 46-year-old man has mild renal failure and hypeension which is proving difficult to manage. CT scan shows both a small adrenal tumor and bilateral hyperplasia. Which of the following is the best test to make a definitive diagnosis? \nSelect and explain. \nA. Dexamethasone suppression test, B. NP-59 adrenal scintigraph, C. Adrenal MRI, D. Selective adrenal vein sampling', 'role': 'user'}, {'content': "Answer: D \nExplanation: Option A- Useful for diagnosis of Cushing syndrome Option B- Used for the diagnosis of Pheochromocytoma (which doesn't have renal failure) C/P given as B/L hyperplasia + Small adrenal tumor = ADRENAL ADENOMA (cause of Conn's Syndrome) Option C- Since CT scan has already been done so MRI is not that useful. Option D- useful as it can enable us to see the hormones produced by the tumor.", 'role': 'assistant'}]