Background: Calcitonin (CT) is a peptidic hormone produced by the thyroid C cells and related to calcium metabolism. High plasmatic levels of this hormone are found in patients with medullary thyroid carcinoma, what makes it an excellent tumor marker for this disease. However, there are reports that showed an increase of plasmatic CT levels in patients with other tumors, mainly in lung cancer.
Purpose: These data prompt us to investigate the validity of the CT level determinations as a potential tumor marker in different histologic lung cancer, and its correlation with hypercalcemia, a very common complication in these tumors.
Method: Blood were sampled from 56 patients with malignant lung disease for the CT and ionized calcium determinations. Calcitonin was measured using a specific radioimmunoassay for the monomeric form of the molecule, in a previous silica extracted serum probe.
Results: We did not find elevated levels of monomeric CT in lung cancer. Only 3 patients had mild elevated levels, while in the others CT was normal or undetectable. Hypercalcemia was found in 21.4% of these patients, but only one with supranormal CT levels.
Conclusion: Monomeric CT serum levels are normal in lung cancer, what makes the latter use an unreliable tumor marker.