This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolic Bone Disease, Subject name: Orthopaedics
[{'content': 'Brown tumor is characteristic of? \nSelect and explain. \nA. Hyperparathyroidism, B. Hypoparathyroidism, C. Hyperthyroidism, D. Hypopituitarism', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. HyperparathyroidismBrown tumor occurs due to the increased osteoclastic activity in hyperparathyroidism. It is a benign mass of reactive tissue.', 'role': 'assistant'}]