The Association Between Nitrite and Nitrate Levels in Drinking Water and Thyroid Dysfunction Biomarkers in Patients with Hypothyroidism: A Cross-Sectional Study in Iran

Introduction: Nitrate and nitrite are prevalent drinking water contaminants that can interfere with iodine uptake and thyroid hormone synthesis, acting as potential endocrine disruptors. Chronic exposure, even at concentrations within international safety limits, has been linked to autoimmune thyroid disorders. This study aimed to assess the association between drinking water nitrate and nitrite levels and serum thyroid autoantibodies—thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TGAb)—in patients with hypothyroidism. Methods: This cross-sectional study analyzed data from ۲۰۱۵ to ۲۰۱۹, integrating water quality records from the Fars Water and Wastewater Company and clinical data from hypothyroid patients attending the Jahrom endocrinology clinic. Serum TPOAb and TGAb levels were measured using chemiluminescent and ELISA methods, respectively. Results: A total of ۳۲ hypothyroid patients (۹ males, ۲۳ females; mean age ۳۳.۲ ± ۹.۹ years) were included. Median TPOAb and TGAb levels were ۲۹۷.۹ and ۴۱.۱ IU/mL, respectively. The median nitrate and nitrite concentrations in drinking water were ۲۵.۱ and ۰.۰۲ mg/L, both within the WHO limits. A significant positive correlation was observed between nitrate levels and TPOAb concentrations (r = ۰.۷۱۴, P = ۰.۰۰۱), whereas no significant correlation was found between nitrite and TPOAb concentrations. Conclusion: The findings suggest that long-term exposure to nitrate, even below regulatory limits, may contribute to autoimmune thyroid activation in hypothyroid patients. Continuous monitoring of nitrate in drinking water and future population-based, longitudinal studies are warranted to clarify causal mechanisms and inform public health interventions.

کلیدواژه ها:

Hypothyroidism ، Drinking water ، Environmental exposure