A hormone, produced by the THYROID GLAND, which is involved in the metabolism of bone, acting to lower the CALCIUM and PHOSPHATE concentrations in the blood. Calcitonin is given by injection in the treatment of some patients with HYPERCALCAEMIA (especially when associated with malignant disease). In severe cases of PAGET'S DISEASE it is used mainly for pain relief, but also relieves some of the neurological complications such as deafness.