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
Brown tumor is characteristic of? 
Select and explain. 
A. Hyperparathyroidism, B. Hypoparathyroidism, C. Hyperthyroidism, D. Hypopituitarism
A: Hyperparathyroidism
Answer: A: Hyperparathyroidism 
Explanation: Ans. A. HyperparathyroidismBrown tumor occurs due to the increased osteoclastic activity in hyperparathyroidism. It is a benign mass of reactive tissue.