<prompt> Calcitonin is produced byThyroidPituitaryPancreasHypothalamus  <response>: Calcitonin also known as thyrocalcitonin is a 32-amino acid linear polypeptide hormone that is produced in humans primarily by the parafollicular cells 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. Calcitonin has been found in fish, reptiles, birds, and mammals. Ref: Ganong;s review of medical physiology; 24th edition; page no-377 