The Calcitonin Test is a diagnostic tool used to measure the levels of calcitonin, a hormone produced by the C cells in the thyroid gland. This test is primarily employed to detect and monitor medullary thyroid cancer (MTC), a rare form of thyroid cancer that arises from these specific cells. Calcitonin levels are typically elevated in individuals with MTC, and the test helps in the early detection, diagnosis, and management of the disease. Additionally, the test may be used to evaluate individuals with a family history of MTC or those with thyroid nodules.