Serum calcitonin, thyrotropin, and goiter

Objective: Recent papers reported that basal calcitonin (CT) level may be related to thyroid volume. This study aims to evaluate if this finding is confirmed in patients undergoing ultrasonography-guided fine-needle aspiration cytology (FNAC) for thyroid nodules. Design: Retrospective university-center study. Methods: From February 2010 to September 2012, 561 patients underwent ultrasonography-guided FNAC and a complete evaluation including basal serum FT4, FT3, TSH, CT and estimation of thyroid volume. Results: The mean thyroid volume was 21.10±9.58 ml in males and 13.42±6.48 ml in females (P<0.001). Thyroid was found to be atrophic in 18 cases and goiter was diagnosed in 128 patients. A linear regression analysis was performed between serum CT levels and thyroid volume, showing a weak direct relationship (R2=0.023, P<0.001). There is no correlation between serum TSH and CT levels. In patients grouped according to morphologic diagnosis (atrophy, normal volume and goiter), CT levels are slightly higher in the high-volume groups: the mean value was 2.02±0.09 in the atrophy group, 2.86±1.73 in the normal volume group, and 3.00±1.66 in the goiter group (P=0.02). When males and females are computed separately, the statistical significance is lost. Conclusions: The small difference in basal CT levels is probably due to a genetically determined higher thyroid volume and increased number of C-cells rather than to acquired goiter. Gender may act as a ‘surrogate marker’ of thyroid volume and the application of a gender-specific cut-off can probably overcome this issue.