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': 'In hyperparathyroidism, all are seen except \nSelect and explain. \nA. Osteopetrosis, B. Osteoporosis, C. Cysts, D. Brown tumor', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Parathyroid\xa0hormone (PTH), also called parathormone or parathyrin, is a hormone secreted by .... (most, 60-70%, of it in the proximal tubule),\xa0except\xa0in the thin segment of the loop of Henle. .... while secondary\xa0hyperparathyroidism\xa0is an appropriately high PTH level\xa0seen\xa0as a physiological .... "A mouse for\xa0all\xa0reasons".', 'role': 'assistant'}]