What is being tested?This test measures the amount of calcitonin in the blood. The function of calcitonin in the human body is unknown; what is known is that it is a hormone produced by C-cells in the thyroid. The thyroid is a small butterfly-shaped gland that lies over and flat against the windpipe in the throat. It produces several hormones, primarily T4 (thyroxine) and T3 (triiodothyronine), that help control the rate of
metabolism.
In two rare conditions, C-cell hyperplasia and medullary thyroid cancer (MTC), excessive amounts of calcitonin are produced. C-cell hyperplasia is a benign condition that may or may not progress to become MTC. MTC is malignant – it can spread beyond the thyroid and can be difficult to treat if it is not discovered early.
About 75-80% of MTC 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), a syndrome associated with several related diseases, including MTC. The altered RET gene is inherited in an autosomal dominant fashion (only 1 copy of the mutated gene – from either your father or mother – is required to have a greatly increased risk of developing MTC). Most cases of sporadic MTC develop when patients are in their 40s or 50s and the prevalence is higher in women, but inherited MTC affects both sexes equally and can occur at an early age.
