Abstract
This prospective study evaluated the concentrations of basal serum calcitonin (Ctn),
Ctn after stimulation with calcium, and Ctn in the needle washout (FNA-Ctn) as predictors
of sporadic medullary thyroid carcinoma (MTC) in patients with thyroid nodules and
basal Ctn between 10 and 100 pg/ml. Forty-one patients were included in the study.
MTC was diagnosed in only 6 patients (14.6%). None of the patients with basal Ctn≤24.6 pg/ml
(n=26) or stimulated Ctn≤186.5 pg/ml (n=21) had MTC. All patients without MTC had
basal Ctn<47 pg/ml and stimulated Ctn<655.2 pg/ml. Among patients with basal Ctn between
24.6 and 47 pg/ml (n=12), 3 (25%) had MTC. Among patients with stimulated Ctn between
186.5 and 655.2 pg/ml (n=18), 4 (22.2%) had MTC. FNA-Ctn distinguished nodules that
were MTC (n=6) from those that were not (n=60), without overlapping results. In the
calcium stimulation test, 19 patients (46.3%) reported some adverse effect, but none
of them was severe or required specific treatment. Our results highlight that in patients
without a history suspicious for MTC, mild or moderate basal hypercalcitoninemia should
not establish the diagnosis of this tumor. Depending on the concentration found, basal
Ctn should be sufficient to define patient management. In doubtful cases, FNA-Ctn
seems to be the best diagnostic test. Calcium stimulation testing was safe, but more
studies are needed to determine the Ctn cutoff after stimulation with calcium.
Key words thyroid nodule - hypercalcitoninemia - calcium stimulation test - medullary thyroid
carcinoma