Calcitonin as a tumor marker. When do you test its levels?

Tumor markers are very important indicators that are tested as a part of cancer diagnostics. One of the markers commonly checked is calcitonin - higher than normal calcitonin levels can confirm the presence of a neoplastic disease or detect disease recurrance following treatment.

Calcitonin - what is it?

Calcitonin is a polypeptide hormone that is composed of 32 amino acids. Unlike many other hormones, the production of calcitonin is not regulated by the pituitary gland. Instread it is directly produced by the thyroid gland - more precisely by the follicular cells (C cells). The production of calcitoning is closely linked to blood calcium levels. Thyroid C-cells have special receptors that detect rising blood calcium levels and in turn increase calcitonin production. Conversely, a decrease in calcium ions in the blood reduces the secretion of the calcitonin.

Calcitonin - hormone’s function

Calcitonin is responsible for the proper functioning of the phosphorus-calcium balance by regulating the concentration of calcium in the blood. The main action of calcitonin is to inhibit calcium resorption and thus prevent bone decalcification. A higher concentration of blood calcium ions stimulates the thyroid gland to secrete calcitonin, which in turn acts to reduce blood calcium levels. Calcitonin exerts its effects mailny through stopping osteoclasts from demineralizing bones. Additionally, calcitonin reduces tubular reabsorption of calcium, phosphorus, and sodium in the kidneys and also reduces gastric acid secretion.

Calcitonin - increased levels

Calcitonin production may be elevated in case of excessive growth of C cells (non-cancerous), or due to the presence of a specific type of thyroid cancer - medullary thyroid carcinoma.

Symptoms of medullary thyroid cancer include:

• palpable lump in the neck,
• soreness of the thyroid gland
• swallowing problems
• hoarseness,
• diarrhea,
• enlargement of cervical lymph nodes (lymph nodes of the neck).

High levels of calcitonin can also occur in other diseases, for example in hyperparathyroidism, hypergastrinaemia, renal dysfunction, lung diseases, pancreatic and respiratory neuroendocrine neoplasms, as well as melanoma and leukemia. Higher concentrations of calcitonin are also observed during pregnancy and lactation. They tend to rise during labour and may be transiently elevated in newborns. Sometimes calcitonin levels may rise after exercise. Calcitonin can also be produced by some lung tumors.

Calcitonin and medullary thyroid cancer

Calcitonin is a very specific tumor marker that allows the detection of thyroid neoplasms. Malignancies such as medullary thyroid cancer often increase the secretion of calcitonin. Medullary thyroid cancer itself is a rare malignancy, and may develop as part of a genetic predisposition (like MEN2) or be the result of a spontaneous mutation.

More about thyroid cancer: Thyroid tumor - symptoms, diagnosis, treatment

Calcitonin - diagnosis

In order to measure calcitonin levels, it is necessary to take a blood sample, which is then sent to the laboratory. Indications for calcitonin testing include::

Diagnostics of thyroid cancer in patients with nodules;
Screening for hereditary medullary thyroid cancer;
Post-operative monitoring for medullary thyroid cancer - increase in calcitonin concentration is associated with recurrance of the disease.

More about tests worth doing as part of cancer prevention: Cancer prevention - what tests should be performed?

Calcitonin - what are the normal levels?

Normal values of calcitonin in the blood depend on both age and gender. Infant blood levels of calcitonin are high, then drop rapidly during childhood, and remain relatively constant throughout the rest of the life. Calcitonin levels tend to be higher in people with a higher body weight. Calcitonin levels may be increased in patients with chronic renal failure and hyperparathyroidism, leukemia and less common disorders such as: myeloproliferative syndrome, Zollinger-Ellison syndrome, autoimmune thyroiditis, or small cell lung cancer. The use of certain medications (e.g., epinephrine, oral contraceptives) may affect calcitonin levels - make sure you inform your doctor about your medications before the test is ordered.