Calcitonin targets the bones and causes the release of calcium from storage when serum calcium levels are low.
True
False
The correct answer and explanation is:
Correct Answer: False
Calcitonin does not cause the release of calcium from bones. Instead, it lowers blood calcium levels by inhibiting bone resorption. This hormone is produced by the parafollicular cells (C cells) of the thyroid gland and plays a role in calcium homeostasis.
When blood calcium levels are too high, calcitonin is secreted. It acts primarily on the bones, where it inhibits the activity of osteoclasts, the cells responsible for breaking down bone tissue. Normally, osteoclasts dissolve bone matrix and release calcium into the bloodstream. By reducing their activity, calcitonin helps prevent additional calcium from entering the blood. Therefore, it promotes the storage of calcium in the bones rather than its release.
In contrast, parathyroid hormone (PTH) has the opposite effect. When blood calcium levels drop, PTH is released from the parathyroid glands. PTH stimulates osteoclasts, enhancing bone resorption and releasing calcium into the blood. It also increases calcium reabsorption in the kidneys and activates vitamin D, which boosts calcium absorption from the intestines.
Calcitonin is more important in short-term regulation of calcium, especially in children or during periods of rapid bone growth. In adults, its role is less critical, as long-term calcium balance is mostly regulated by PTH and vitamin D.
In summary, the statement is false because calcitonin does not release calcium from bones. Instead, it acts to lower blood calcium levels by preventing bone breakdown and promoting calcium deposition in the bone matrix. This mechanism is vital in maintaining normal calcium levels, preventing hypercalcemia, and supporting skeletal health.