Calcitonin is secreted by which gland to help decrease calcium levels in the blood and move calcium into storage in bones and teeth?

• A. Parathyroid glands
• B. Pancreas
• C. Posterior pituitary
• D. Thyroid gland

Answer: (D)

Calcium balance is regulated by hormones that respond to the level of calcium in the blood. When calcium is high, calcitonin helps lower it by slowing bone breakdown and encouraging calcium to move into bone tissue. Calcitonin is produced by the thyroid gland, specifically by the parafollicular (C) cells. That makes the thyroid gland the source describing this action.

The parathyroid glands release parathyroid hormone, which has the opposite effect by raising blood calcium through bone resorption and increased kidney reabsorption. The pancreas and the posterior pituitary are not primary regulators of blood calcium in this way.