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: Medicine
[{'content': 'Not seen in hyperparathyroidism \nSelect and explain. \nA. Increase in serum calcium, B. Increase in serum calcitonin, C. Subperiosteol resorption of phalanges, D. Increase in 24 hr urinary calcium excretion > 250', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]