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 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.