What role does calcitonin play in the body?

Calcitonin plays a crucial role in maintaining calcium homeostasis in the body by decreasing blood calcium levels. It is a hormone secreted by the parafollicular cells (C cells) of the thyroid gland. Its primary action is to inhibit the activity of osteoclasts, which are the cells responsible for bone resorption or breakdown. When osteoclast activity is inhibited, less calcium is released from bones into the bloodstream, leading to a decrease in blood calcium levels.

This action of calcitonin is particularly important during periods of high calcium levels, as it helps to prevent hypercalcemia. By promoting the storage of calcium in bone and reducing the levels of calcium circulating in the blood, calcitonin works in conjunction with parathyroid hormone (PTH), which exerts opposite effects by increasing blood calcium levels.

Hence, the statement that calcitonin decreases blood calcium levels by inhibiting osteoclast activity accurately reflects its physiological function.