The calcitonin determination is intended to be used as an aid in the diagnosis and treatment of diseases involving the thyroid and parathyroid glands, including carcinoma and hyperparathyroidism in conjunction with other clinical and laboratory findings.
Human calcitonin (hCT) is a 32 amino acid peptide hormone with a molecular mass of 3418 daltons which is secreted primarily by the parafollicular C cells of the thyroid gland. 1 It is metabolized in the liver and kidney and regulated by serum calcium levels. Physiologically hCT has effects on calcium and phosphorus metabolism. It is an inhibitor of bone resorption to prevent bone loss at times of calcium stress (e.g. pregnancy, lactation and growth).
Serum hCT levels are relatively high in infants, decline rapidly and are relatively stable from childhood through adult life. In general hCT serum levels are higher in men than in women whereas smoking may lead to an additional increase in serum calcitonin levels.
Elevated levels of hCT can be found in various pathological conditions e.g. medullary thyroid carcinoma, a tumor of the calcitonin secreting cells of the thyroid. It is also frequently elevated in leukemic and myeloproliferative disorders 7 or may be produced ectopically in tumors like lung (small cell lung cancer) or breast cancer. Furthermore elevated levels can also be found in conjunction with hyperparathyroidism, hypergastrinemia, renal failure and chronic inflammatory disease.
The most prominent clinical syndrome associated with a disordered hypersecretion of hCT is the medullary thyroid carcinoma (MTC), which comprises 5‑10 % of all thyroid cancers. It may occur sporadically or in a familial form that is inherited as an autosomal dominant trait. Furthermore, calcitonin measurements can also be used to monitor the efficacy of therapy in patients with calcitonin producing tumors. In a small but increasing percentage of patients, however, basal hormone levels are indistinguishable from normal. Some of these subjects represent the early stages of C‑cell neoplasia or hyperplasia that are most amenable to surgical cure. To identify these patients in an early disease stage, provocative tests for hCT secretion are necessary to exclude false negative diagnosed patients. Most tumors respond with an increase of hCT levels after administration of calcium or pentagastrin or the combination of both.