How do calcitonin and denosumab differ in mechanism and typical use?

• A. Calcitonin directly inhibits osteoclast activity; denosumab inhibits RANKL, decreasing osteoclast formation and activity; denosumab is given by injection every 6 months.
• B. Denosumab inhibits osteoclasts; calcitonin inhibits osteoblasts; both are taken orally.
• C. Calcitonin increases calcium absorption; denosumab promotes bone loss.
• D. Calcitonin and denosumab have identical mechanisms.

Answer: (A)

Understanding how these two drugs work is the key. Calcitonin lowers bone resorption by acting directly on osteoclasts, reducing their activity. It’s used in osteoporosis but isn’t a first‑line choice because its efficacy is modest and it can be given intranasally or by injection, not as a convenient oral pill for long-term control. Denosumab, on the other hand, is a monoclonal antibody that targets RANKL. By blocking RANKL, it prevents the formation and activity of osteoclasts, leading to a stronger reduction in bone resorption. For osteoporosis, it’s given as a subcutaneous injection about every six months, which matches the dosing described.

That combination of mechanism and dosing is why the statement is correct. The other options misstate one or more facts: calcitonin does not inhibit osteoblasts, denosumab is not taken orally, and the two do not have identical actions.