Int J Thyroidol.  2020 Nov;13(2):118-127. 10.11106/ijt.2020.13.2.118.

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

  • 1Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul, Korea
  • 2Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
  • 3Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea
  • 4Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea
  • 5Department of Internal Medicine, Seoul National University Boramae Medical Center, Seoul, Korea
  • 6Department of Preventive Medicine, College of Korean Medicine, Dongguk University, Gyeongju, Korea
  • 7National Evidence-Based Healthcare Collaborating Agency, Seoul, Korea


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.
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.
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.


Thyroid nodule; Size; Iodine; Diffuse parenchymal abnormality
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