This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
[{'content': 'Not a marker for hyperparathyroidism is - \nSelect and explain. \nA. Increase in serum calcium, B. Increase in 24 hour urinary calcium excretion, C. Increase in serum calcitonin, D. Subperiosteal resorption of phalanges', 'role': 'user'}, {'content': 'Answer: C \nExplanation: markers include increased serum calcium, 24-hr urinary calcium , creatinine clearance, bone mineral density ( Harrison 17 pg 2383)', 'role': 'assistant'}]