Calcitonin is a polypeptide hormone secreted by the C-cells of the thyroid gland. The main action of calcitonin is to inhibit bone resorption. It achieves this effect by regulating the number and activity of osteoclastsw, or bone-destroying cells.
Calcitonin is secreted in response to elevated serum calcium levels, thereby reducing serum calcium levels, in part by increasing excretion by the kidneys. However, the role of calcitonin in regulating calcium levels is insignificant in comparison with the effects of parathyroid hormones s. Therefore, it is not used in the study of disorders of calcium homeostasis.
Calcitonin is a specific and sensitive tumor marker. Malignant tumors arising from thyroid cells (medullary thyroid carcinoma) usually secrete increased amounts of calcitonin. Medullary thyroid cancer is a rare malignancy and may be associated with a genetic family predisposition or the result of a spontaneous mutation. The major tumor marker for diagnosing and monitoring its development is calcitonin.
Serum calcitonin concentrations are high in infancy, decline rapidly in childhood, and remain relatively stable throughout the rest of life. As a general rule, serum calcitonin concentrations are higher in individualsb with higher body weights.
Serum calcitonin levels are higher in individuals with higher body weights
Calcitonin levels may be increased in patientswith chronic renal failure and hyperparathyroidism, leukemia and less common disorders such as myeloproliferative syndrome, Zollinger-Ellison syndrome, autoimmune thyroiditis, small-celllung cancer.
Calcitonin test
Calcitonin testing finds applications in cases such as:
- diagnosis of clinically symptomatic thyroid cancer in patientswith „cold” nodules or nodules with inconclusive histology (e.g., suspected anaplastic carcinoma);
- family screening for cases of hereditary medullary thyroid cancer;
- Postoperative monitoring of medullary thyroid cancer. Calcitonin concentration correlates with tumor mass. A doubling of the concentration is associated with tumor recurrence;
- monitoring patientsw with neuroendocrine tumors: carcinoma, insulinoma, small-celllung cancer. In them, calcitonin secretion may be part of the paraneoplastic syndrome, i.e., symptomsw independent of local tumor growth.
This test is not useful for evaluating calcium metabolism disorders.
When should calcitonin testing be performed?
Testing calcitonin levels is recommended for thyroid cancer. In the early stages, an increase in its concentration usually causes no symptomsw. As thyroid cancer grows, the following may appear:
- a lump thatry can be felt through the skinhand of the neck;
- change in voice, including increased hoarseness;
- difficulty associated with swallowing;
- bl of the neck and throat;
- swelling of the lymph nodesneck;
Preparation before the test
The examination does not require any prior preparation.
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