This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrine System, Subject name: Physiology
Osteoclast has specific receptor for: 
Select and explain. 
A. Parathyroid hormone, B. Calcitonin, C. Thyroxin, D. Vit D3
B: Calcitonin
Answer: B: Calcitonin 
Explanation: Calcitonin receptor is expressed in osteoclasts. Calcitonin inhibits bone resorption by inhibiting osteoclasts; and promotes Ca2+ from blood to be deposited on the bone. This decreases blood Ca2+. PTH is a primary endocrine regulator of bone remodeling in adults. The PTH/PTHrP receptor is expressed on osteoblasts, but not on osteoclasts.