Potential role of iodine excess in papillary thyroid cancer and benign thyroid tumor: A case-control study.

Background And Objectives: The relationship between nutritional status of iodine and thyroid tumor is unclear. We investigated the association between urinary iodine concentration and thyroid function in patients with papillary thyroid cancer, benign thyroid tumor and healthy individuals.

Methods And Study Design: We compared the biomarkers of thyroid function and urinary iodine concentration within and between each group. A regression analysis was used to identify risk factors for papillary thyroid cancer. Correlation analysis was performed to determine whether any significant correlation exists between urinary iodine concentration and thyroid function biomarkers.

Results: The iodine nutrition statuses of these three groups were adequate (median urinary iodine concentration= 100-199 μg/L). However, the median urinary iodine concentration of papillary thyroid cancer (174.7 μg/L) and benign thyroid tumor (165.04 μg/L) groups was significantly higher than that of the healthy control group (135.8 μg/L) (p<0.05). The regression analysis showed that thyroglobulin antibody was an independent risk factor for papillary thyroid cancer. After adjusting for age and gender, the association between thyroglobulin antibody and urinary iodine concentration was significant (β: 0.002; p<0.05). In subgroup analyses, significant correlations was noted only in the papillary thyroid cancer group (adjusted β: 0.002; 95% confidence interval: 0.000- 0.003).

Conclusions: Excessive iodine in patients with thyroid tumors may affect thyroglobulin antibody, which may be an independent risk factor for papillary thyroid cancer.