What mechanism does Calcitonin use to adjust blood calcium levels?

• A. Stimulates calcium absorption
• B. Inhibits osteoclast activity
• C. Enhances vitamin D production
• D. Promotes excessive calcification

Answer: (B)

Calcitonin is a hormone produced by the thyroid gland that plays a key role in regulating calcium levels in the blood. Its primary mechanism of action is to inhibit osteoclast activity. Osteoclasts are the cells responsible for the breakdown of bone tissue, a process that releases calcium into the bloodstream. By inhibiting these cells, calcitonin effectively reduces the release of calcium from bones, leading to a decrease in blood calcium levels.

This regulation is crucial, especially during times when calcium levels in the blood are high, as it helps to maintain homeostasis and prevents potential complications resulting from hypercalcemia. Thus, by directly targeting osteoclasts, calcitonin serves as a protective mechanism against elevated calcium levels and supports overall bone health.

The other choices involve different processes: stimulating calcium absorption would relate more to the actions of parathyroid hormone or vitamin D, enhancing vitamin D production is not a function of calcitonin itself, and promoting excessive calcification is not consistent with the role of calcitonin, which is to reduce calcium concentration in the blood rather than promote its accumulation in bones.