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: Physiology
Osteoclasts are inhibited by: 
Select and explain. 
A. Parathyroid hormone, B. Calcitonin, C. 1,25-dihydroxycholecalciferol, D. Tumor necrosis factor
B: Calcitonin
Answer: B: Calcitonin 
Explanation: Calcitonin inhibits bone resorption by direct action on osteoclasts. Ref: Ganong's Review of Medical Physiology, 21st Edition, Page 397