calcitonin
Hormone produced by thyroid C cells that regulates calcium metabolism and serves as a tumor marker for medullary thyroid carcinoma.
Full Definition
Calcitonin is a 32-amino acid peptide hormone produced by the parafollicular C cells of the thyroid gland in response to elevated serum calcium levels. Its primary physiological function is to lower blood calcium by inhibiting osteoclast activity and promoting calcium excretion by the kidneys. In clinical practice, calcitonin serves as an important tumor marker for medullary thyroid carcinoma, as these tumors often secrete excessive amounts of the hormone. Elevated calcitonin levels may also be seen in other conditions including C-cell hyperplasia, chronic kidney disease, and certain medications. Baseline and stimulated calcitonin measurements are used for diagnosis and postoperative surveillance.
Usage
Usage note: May be called thyrocalcitonin in older literature; calcitonin is the preferred modern term.
In Context
- "Baseline calcitonin levels were markedly elevated, suggesting medullary thyroid carcinoma." — laboratory report
- "Postoperative calcitonin monitoring is essential for detecting MTC recurrence." — follow-up protocol