Association of serum calcitonin levels with multinodular thyroid disease: 10-year single center experience

Background. From 2005 to 2015 routine calcitonin (CT) screening was performed in our department in all patients with multinodular goiter (MNG) using the same assay.

Aim. We investigated possible associations between unstimulated serum CT levels and the presence of either thyroid autoimmunity (AITD) or thyroid neoplasia.

Methods. This is a retrospective study of 648 patients (559 female [F] 86.3%, 89 male [M] 13.7%, age range 18-89, median 58 years,). CT≤4.6 pg/ml [F] and ≤11.5 pg/ml [M] was defined as normal. Patients were stratified into 4 groups according to CT. Group1: CT<0.05 (undetectable), Group2: CT [F&M] within normal range, Group3: CT:4.7-10 [F] & 11.6-20 [M], Group4: CT>10 [F] & >20 [M]. Furthermore patients were subcategorized in those with Autoimmune Thyroid Disease (AITD) and those without (non-AITD).

Results. The distribution of patients was: Group1: n=186 (28.7%), Group2: n=422 (65.1%), Group3: n=29 (4.5%), Group4: n=11 (1.7%). Of the patients with AITD history 23.4% belonged to Group1, 68.6% to Group2, 6.4% to Group3 and 1.6% to Group4 (x2, p=0.037). Forty seven patients (7.3%) underwent total thyroidectomy. Histopathological examination revealed: Medullary Thyroid Carcinoma (MTC) n=3 (3/3 Group4), C-Cell Hyperplasia (CCH) n=5 (3/5 Group3, 2/5 Group4), Papillary Thyroid Carcinoma (PTC) n=17 (7/17 Group1, 10/17 Group2), MNG n=22 (8/22 Group1, 10/22 Group2, 2/22 Group3, 2/22 Group4). 2/5 patients with CCH had PTC. 1/17 PTC patient had mixed PTC-MTC. Patients with MTC had remarkably higher CT levels (253-1222 pg/ml) compared to those with CCH (5.8-16.1 pg/ml).

Conclusions. This study reaffirms the positive correlation between CT levels and the presence of MTC or CCH, clearly and conspicuously distinguished by the range of CT levels, albeit in a small number of patients with these diagnoses. Patients with AITD have more frequently detectable or slightly increased CT levels.