Final answer:
Calcitonin inhibits osteoclasts, stimulates osteoblasts, and promotes calcium excretion by the kidneys to add calcium to the bones.
Step-by-step explanation:
The hormone calcitonin, which is produced by the parafollicular or C cells of the thyroid, inhibits osteoclasts, stimulates osteoblasts, and stimulates calcium excretion by the kidneys. These actions result in calcium being added to the bones to promote structural integrity. Calcitonin is most important in children, during pregnancy, and during prolonged starvation. In healthy nonpregnant, unstarved adults, the role of calcitonin is unclear.