calcitonin
Pronunciation: kal-si-TOH-nin
A hormone produced by thyroid C cells that serves as a tumor marker for medullary thyroid carcinoma.
Full Definition
Calcitonin is a 32-amino acid polypeptide hormone primarily produced by the parafollicular C cells of the thyroid gland. While its physiological role in calcium homeostasis is minimal in humans, calcitonin serves as an important tumor marker for medullary thyroid carcinoma (MTC). Elevated basal serum calcitonin levels or abnormal responses to provocative testing (with calcium or pentagastrin) can indicate C cell hyperplasia or MTC. Normal calcitonin levels are typically less than 10 pg/mL in most assays, though reference ranges vary by laboratory and gender. Serial calcitonin measurements are used for MTC surveillance following thyroidectomy, with rising levels suggesting recurrent or persistent disease.
Usage
Usage note: Reference ranges vary significantly between assays; always interpret in context of laboratory-specific values.
In Context
- "Baseline calcitonin levels of 450 pg/mL prompted further evaluation for medullary thyroid carcinoma." — Laboratory interpretation
- "The patient's calcitonin doubled to 200 pg/mL over six months, concerning for MTC recurrence." — Oncology follow-up note