calcitonin /kal′sitō″nin/ [L, calx + Gk, tonos, tone] , a hormone produced in parafollicular cells of the thyroid that participates in regulating the blood level of calcium and stimulates bone mineralization. A synthetic preparation of the hormone is used in the treatment of certain bone disorders. Calcitonin acts to reduce the blood level of calcium and to inhibit bone resorption, whereas parathyroid hormone acts to increase blood calcium level and bone resorption. Vitamin D also contributes to the regulation of calcium homeostasis. Also called salmon calcitonin, thyrocalcitonin.
