Calcitonin is a polypeptide hormone that regulates calcium levels in body fluids. The parafollicular cells or C cells are present in the follicular epithelium of the thyroid gland and secrete calcitonin. While the exact mechanism of calcitonin's actions in calcium homeostasis is unknown, calcitonin has a role in bone calcium storage. It also plays a part in calcium ion absorption in the digestive system. It minimizes the post-meal calcium surge by promoting calcium excretion by the kidneys. Calcitonin is essential during childhood when it stimulates bone growth and mineral deposition. In adults, it also helps prevent bone mass loss during prolonged starvation and later stages of pregnancy.