Calcitonin is a hormone produced by the thyroid gland that helps regulate calcium levels in the body and is involved in the process of bone building. When taken by shot or nasal spray, it slows the rate of bone thinning related to osteoporosis.

Calcitonin levels in the blood drop after a person has his or her thyroid gland removed. However, medication is not needed to replace this lost hormone.

Calcitonin sometimes is used as treatment to relieve pain from spinal fractures related to osteoporosis. It is not known how calcitonin decreases pain.