This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bone and Imaging, Subject name: Orthopaedics
Osteitis fibrosa cystica is seen in: 
Select and explain. 
A. Hyperparathyroidism, B. Hypoparathyroidism, C. Hypothyroidism, D. Hypehyroidism
A: Hyperparathyroidism
Answer: A: Hyperparathyroidism 
Explanation: Brown tumor /osteitis fibrosa cystica One of the manifestations of Hyperparathyroidism Bony trabeculae are replaced by fibrous tissue and there is cystica that is cystic cavity in bone filled with blood and blood degradation products giving it brown color. Hemosiderin impas the brown color (hence the name of the lesions) Histologically brown tumors are identical to GCTs (both are osteoclastomas),