This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Musculoskeletal system, Subject name: Anatomy
Osteoclast are stimulated by 
Select and explain. 
A. Thyroxine, B. PTH, C. Calcitonin, D. Estrogen
B: PTH
Answer: B: PTH 
Explanation: Refer Robbins page no 1207-1208 Parathyroid hormone related protein (PTHrP) is a local factor, expressed by perichondrial stromal cells and early proliferating chondrocytes, that activates the PTH receptor and maintains proliferation of chondrocytes.