Which hormone lowers the level of calcium in the blood by depositing calcium into the bone?

Calcitonin is the hormone that specifically lowers calcium levels in the blood by promoting the deposition of calcium into the bones. When blood calcium levels rise, calcitonin is released from the thyroid gland. It acts largely on osteoblasts, which are the cells responsible for bone formation, stimulating them to absorb calcium from the bloodstream and incorporate it into the bone matrix. This process not only decreases blood calcium levels but also strengthens bones.

In contrast, parathyroid hormone plays a critical role in increasing calcium levels in the blood by stimulating the release of calcium from bones, increasing calcium reabsorption in the kidneys, and promoting the activation of vitamin D. Growth hormone primarily affects overall growth and metabolism rather than directly regulating calcium levels. Thyroxine, a hormone produced by the thyroid gland, influences metabolic rate and growth but does not have a direct role in calcium regulation in the same manner as calcitonin.