Fluoride Exposure and Thyroid Function among Iodine Deficient Adults in Canada

Background: Fluoride exposure has the potential to disrupt thyroid functioning, though adequate iodine intake may mitigate this effect. This study is the first population-based study to examine the impact of chronic low-level fluoride exposure on thyroid function, while considering iodine status.Objective: This study used weighted population-based data from Cycle 3 (2012-2013) of the Canadian Health Measures Survey (CMHS), a cross-sectional survey designed to collect health and wellness data and biological specimens on Canadians.Methods: The weighted sample represented 7,543,966 adults aged 18-79 who were not taking any thyroid-related medication. Urinary fluoride concentrations were measured in spot samples using an ion selective electrode and adjusted for specific gravity (UFSG) and creatinine (UFCR). Serum TSH levels provided a measure of thyroid function. Multivariable regression analyses examined the relationship between adjusted levels of urinary fluoride and TSH, controlling for covariates. We test...