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Etienne Cavalier, Agnès Carlisi, Jean-Paul Chapelle, Pierre Delanaye, Analytical Quality of Calcitonin Determination and Its Effect on the Adequacy of Screening for Medullary Carcinoma of the Thyroid, Clinical Chemistry, Volume 54, Issue 5, 1 May 2008, Pages 929–930, https://doi.org/10.1373/clinchem.2007.100636
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To the Editor:
Calcitonin, a 32–amino acid calcium-lowering peptide secreted by the C cells (parafollicular cells) of the thyroid, is used as a marker for medullary carcinoma of the thyroid (MCT). However, calcitonin is not specific for MCT, because it is also secreted by other neoplasms, including breast cancer and small cell lung cancer.
Secretion of calcitonin is regulated primarily by the concentration of extracellular calcium, but can also be stimulated by gastrin. Although calcitonin concentrations are higher in men than in women and tend to decline with age, many laboratories use a cutoff value of 10 ng/L instead of a population-based reference interval. Prior studies have shown that basal calcitonin concentrations are below this threshold in a normal population(1)(2) and in 90% of patients suffering from other nodular thyroid diseases(3). In clinical practice, a patient with a calcitonin concentration higher than 10 ng/L should undergo a pentagastrin test to exclude MCT.