Changes of Nodular Size and Its Risk Factors in Iodine-Sufficient Area: a Retrospective Cohort Analysis of 7753 Thyroid Nodules

ABSTRACT

Background and Objectives@#Iodine is known to be an important factor in the occurrence of goiter, and South Korea is a region with sufficient iodine supplementation. In this regard, we checked the size change of thyroid nodules found by health check-up in Koreans and examined which risk factors influence the size change. @*Materials and Methods@#A total 7753 subjects who underwent thyroid sonography two or more times were included. We defined that there was a change in the size of the nodule when the difference in diameter identified in the last ultrasound was more than 3 mm. @*Results@#Thyroid nodules were decreased in 895 subjects (11.5%) and increased in 1041 subjects (13.5%). The rate of increased nodule was on an increasing trend according to the duration (annual percent change 2.6%, p＜0.001). In contrast, the rate of decreased nodule was unchanged. Predictive factors related to decrease of the nodule size were young age, male sex, larger initial nodule size and thyroiditis. Similarly, young age, larger initial nodule size and diffuse parenchymal abnormality were significant predictive factors for increased nodules. However, diffuse parenchymal abnormality was not a predictive factor when we analyzed only thyroid nodules larger than 1 cm. @*Conclusion@#In our study, 11.5-13.5% of benign thyroid nodules were increased or decreased during median 27 months of follow-up in iodine sufficient condition. Young age, larger initial size and diffuse parenchymal abnormality were common predictive factor affecting both the increase and decrease of thyroid nodules.