Serum thyroglobulin, a biomarker for iodine deficiency, is not associated with increased risk of upper gastrointestinal cancers in a large Chinese cohort.

Iodine concentrates in gastric tissue and may act as an antioxidant for the stomach. We previously showed that self-reported goiter was associated with significantly increased risk of gastric noncardia adenocarcinoma (GNCA) and nonsignificantly increased risks of gastric cardia adenocarcinoma (GCA) and esophageal squamous cell carcinoma (ESCC) in a prospective case-cohort study in a high-risk population in China. Negatively correlated with iodine levels, serum thyroglobulin (Tg) is a more sensitive biomarker of iodine deficiency than goiter. Our study aimed to determine whether baseline serum Tg was also associated with development of GNCA, GCA and ESCC in the same cohort, the Linxian General Population Nutrition Intervention Trial. Sera from ∼200 subjects of each case type and 400 noncases were tested for serum Tg concentration using appropriate assays. Tg was modeled as sex- and assay-specific quartiles in Cox regression models adjusted for age, smoking, alcohol, Helicobacter pylori status, pepsinogens I/II ratio, family history and commune of residence. In the final combined analysis, participants in the highest quartile of serum Tg, compared to those in the lowest quartile, had adjusted hazard ratios of 0.88 (95% confidence interval 0.50-1.52), 1.14 (0.63-2.05) and 0.78 (0.47-1.31) for GNCA, GCA and ESCC, respectively. Using serum Tg, a sensitive biomarker of iodine deficiency, we found no association between serum Tg concentrations and risk of these upper gastrointestinal (UGI) cancers in the study population. Our results do not support the hypothesis that iodine deficiency, as assessed by serum Tg, is associated with an increased risk of UGI cancers.