calcitonin

n. (Medicine) hormone that is produced in the thyroid gland and serves to regulate blood calcium levels (given as a medication to treat hypercalcemia)

Calcitonin is a 32 amino acid polypeptide hormone that is produced in humans primarily by the parafollicular (also known as C) cells of the thyroid, and in many other animals in the ultimobranchial body. It acts to reduce blood calcium Ca2+, opposing the effects of parathyroid hormone (PTH). It has been found in fish, reptiles, birds and mammals. Its importance in humans has not been as well established as its importance in other animals.
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Calcitonin /cal·ci·to·nin/ a polypeptide hormone secreted by C cells of the thyroid gland, and sometimes of the thymus and parathyroids, which [more]Calcitonin - Community and Resources

Noun
1. thyroid hormone that tends to lower the level of calcium in the blood plasma and inhibit resorption of bone
(synonym) thyrocalcitonin
(hypernym) thyroid hormone

A hormone formed by the C cells of the thyroid gland. It helps maintain a healthy level of calcium in the blood. When the calcium level is too high, calcitonin lowers it.