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C1 Esterase Inhibitor C Reactive Protein C Reactive Protein High Sensitivity CA 125 CA 153 CA 19.9 CA 27.29 Caffeine Calcitonin Calcium Calcium Ionized Carbamazepine Carbon Dioxide Carbon Monoxide Carcinoembryonic Antigen Cardiac Marker Panel Cardiovascular Risk Panel Carotene CCP Antibody CD4 Enumeration Celiac Disease Panel Centromere Antibody Cephalothin Antibody Cerebrospinal Fluid Ceruloplasmin Chemistry Panels Chlamydia Detection Chloride Cholesterol Cholinesterase Clindamycin Resistance Clostridium Difficile Coagulation Factor Assays Coagulation Factor Inhibitor Coagulation Screen Cold Agglutinin Titer Colloid Osmotic Pressure Complement Profile Complete Blood Count Congenital Adrenal Hyperplasia Cord Blood Gases Cord Blood Studies Corticotropin Releasing Hormone Stimulation Test Cortisol Cortisol in Critical Illness Cortisol Salivary Cortisol Urine Free Cortrosyn Stimulation Test Cotinine Creatine Kinase Creatine Kinase MB Creatinine Creatinine Clearance Crossmatch CRP Cryoglobulin Cryptococcal Antigen Cryptosporidium Antigen Crystal Identification Cushing Syndrome Cyclosporine Cystic Fibrosis Cytogenetic Studies Cytomegalovirus Antibody Cytomegalovirus Culture Cytomegalovirus PCR Qualitative Cytomegalovirus PCR Quantitative

Calcitonin

Calcitonin is a polypeptide hormone secreted by the parafollicular, or C cells, of the thyroid. Its main action is inhibition of bone resorption by regulating the number and activity of osteoclasts. Calcitonin is secreted in direct response to plasma hypercalcemia and prevents large oscillations in plasma calcium levels and excessive loss of body calcium. However, compared to parathyroid hormone and 1,25 OH-vitamin D, calcitonin plays a minor role in plasma calcium regulation. Measurement of plasma calcitonin levels is not useful in the diagnosis of hyper or hypocalcemia.

Medullary thyroid carcinoma usually produces elevated calcitonin levels. Medullary carcinoma is uncommon, comprising only 5% of thyroid malignancies. Approximately 25% of cases are familial. It the families do not manifest other endocrine dysfunction, it is called familial medullary thyroid carcinoma. However, medullary carcinoma also occurs as a component of multiple endocrine neoplasia type II (MEN II). Most patients with sproradic medullary thyroid cancer have high plasma calcitonin levels. Approximately 30% of patients with familial medullary thyroid cancer have normal levels. Previously, these patients required a calcium infusion provocative tests to demonstrate the abnormality. However, today this test has been replaced by detection of the RET proto-oncogene.

Following successful surgical removal of medullary carcinoma, plasma calcitonin levels fall into the undetectable range over a variable period of several weeks. Persistently elevated levels indicate incomplete cure. A rise in previously undetectable or very low postoperative plasma calcitonin levels is highly suggestive of disease recurrence.

Calcitonin may rarely be secreted by islet cell tumors, carcinoid tumors, or cancers of the lung, breast or pancreas. It may also be elevated in chronic renal failure, pernicious anemia, pregnancy at term, and in newborns.

Reference range is < 8 pg/mL in females and < 16 pg/mL in males.

Specimen requirement is one green-top (heparin) tube of blood from a fasting patient.