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: Orthopaedics
Brown a tumour is seen in 
Select and explain. 
A. Hypothyroidism, B. Hyperparathyroidism, C. none, D. all of the above
B: Hyperparathyroidism
Answer: B: Hyperparathyroidism 
Explanation: Brown's tumour is seen in Hyperparathyroidism. 
It's an expansile lytic lesion. This is a collection of osteoclasts.
It commonly found in maxilla and mandible, other bones also affected.
Other features are multiple bone cysts, subperiosteal retraction of bones, salt and pepper appearance of the skull in X-ray.