Relationship between iodine levels and papillary thyroid carcinoma: A systematic review and meta-analysis

Background: Iodine excess has been suggested as an exogenous risk factor of papillary thyroid cancer (PTC). We performed a systematic review and meta-analysis to assess the relationship between iodine exposure measured in various forms and PTC prevalence.

Methods: We searched MEDLINE, Embase, and the Cochrane Library for case-control studies on iodine and PTC published up to December 2015. Exposure to iodine was compared between PTC and control groups.

Results: From the 16 selected studies, the odds ratio (OR) for the overall effect size between high iodine exposure and PTC risk was 1.418 (95% confidence interval [CI] 1.054-1.909). Based on 7 studies conducted in high iodinated regions, a positive association between iodine exposure and PTC was observed (OR 2.200; 95% CI 1.389-3.483).

Conclusion: This study demonstrated a higher exposure to iodine in patients with PTC compared with controls, especially for patients from high iodinated regions.