kalkitonin

Calcitonin, sometimes spelled kalkitonin in some non-English sources, is a peptide hormone produced by the parafollicular C cells of the thyroid gland. In humans it is encoded by the CALCA gene, and a related peptide called calcitonin gene-related peptide (CGRP) is produced from the same gene by alternative splicing in other tissues.

Physiological role: Calcitonin lowers serum calcium by inhibiting osteoclast-mediated bone resorption. Its overall contribution to calcium and phosphate homeostasis in adult humans is modest compared with the actions of parathyroid hormone and vitamin D.

Clinical significance: Calcitonin serves as a tumor marker for medullary thyroid carcinoma (MTC) and C-cell hyperplasia. Baseline serum levels and serial measurements are used in diagnosis and postoperative monitoring. Elevated levels may indicate MTC, though elevations can occur in other conditions such as chronic kidney disease and certain thyroid disorders. Stimulation tests using calcium or secretin have been used in the past to provoke calcitonin release.

Pharmacology and safety: Salmon calcitonin and other calcitonin derivatives have been used as medicines to treat osteoporosis, Paget disease, and hypercalcemia. However, their efficacy is modest and long-term use has been limited by safety concerns, including reports of an increased cancer risk with calcitonin-containing therapies, leading to reduced use in many guidelines.

Laboratory testing: Calcitonin is measured in serum by immunoassay. Reference ranges vary by assay and age, with smoking and renal impairment potentially elevating levels. When elevated, clinicians perform imaging studies to assess for MTC, along with monitoring of related markers such as carcinoembryonic antigen (CEA).