Calcitonin

This test measures the amount of calcitonin in the blood. Calcitonin is a hormone produced by special cells in the thyroid called C-cells. It is involved in the regulation of calcium levels in the blood, and calcitonin inhibits bone breakdown (resorption), although how calcitonin works in the human body is unclear. The thyroid is a small butterfly-shaped gland that lies over and flat against the windpipe in the throat. It produces several hormones that help control the rate of metabolism - primarily thyroxine (T4) and triiodothyronine (T3).

In two rare conditions, C-cell hyperplasia and medullary thyroid cancer, excessive amounts of calcitonin are produced. C-cell hyperplasia is a benign condition that may or may not progress to become medullary thyroid cancer. Medullary thyroid cancer is malignant – it can spread beyond the thyroid and can be difficult to treat if it is not discovered early.

About 75-80% of medullary thyroid cancer cases are sporadic, but about 20-25% are related to an inherited mutation in the RET gene that leads to multiple endocrine neoplasia type 2 (MEN 2). MEN 2 is a syndrome associated with several related diseases, including medullary thyroid cancer and pheochromocytomas. The altered RET gene is inherited in an autosomal dominant fashion. Only one copy of the mutated gene – from either your father or mother – is required to have a greatly increased risk of developing medullary thyroid cancer. Most cases of sporadic medullary thyroid cancer develop when patients are in their 40s or 50s. The prevalence is higher in women, but the inherited form affects both sexes equally and can occur at an early age.

A blood sample is obtained by inserting a needle into a vein in the arm.

No test preparation is needed.