Calcitonin is a hormone produced by the C-cells of the thyroid gland and also known as thyrocalcitonin. High concentration of calcitonin may lead to increase urine excretion of calcium and phosphate which leads to hypocalcaemia. Calcitonin helps to regulate levels of calcium and phosphate in the blood during pregnancy. Increase of calcitonin will cause medullary thyroid cancer. Patients who have removed their thyroid gland will lead to undetectable levels of calcitonin in the blood stream. Symptoms of medullary thyroid cancer: A lump or swelling at the front of the neck, pain at the throat or front of the neck, change in the voice, difficulty swallowing or breathing, persistent cough not associated with a cold.