Impact of Drinking Water Fluoride on Human Thyroid Hormones: A Case- Control Study

The elevated fluoride from drinking water impacts on T₃, T₄ and TSH hormones. The aim was study impacts of drinking water fluoride on T₃, T₄ and TSH hormones inYGA (Yazd Greater Area). In this case- control study 198 cases and 213 controls were selected. Fluoride was determined by the SPADNS Colorimetric Method. T₃, T₄ and TSH hormones tested in the Yazd central laboratory by RIA (Radio Immuno Assay) method. The average amount of TSH and T₃ hormones based on the levels of fluoride in two concentration levels 0-0.29 and 0.3-0.5 (mg/L) was statistically significant (P = 0.001 for controls and P = 0.001 for cases). In multivariate regression logistic analysis, independent variable associated with Hypothyroidism were: gender (odds ratio: 2.5, CI 95%: 1.6-3.9), family history of thyroid disease (odds ratio: 2.7, CI 95%: 1.6-4.6), exercise (odds ratio: 5.34, CI 95%: 3.2-9), Diabetes (odds ratio: 3.7, CI 95%: 1.7-8), Hypertension (odds ratio: 3.2, CI 95%: 1.3-8.2), water consumption (odds ratio: 4, CI 95%: 1.2-14). It was found that fluoride has impacts on TSH, T₃ hormones even in the standard concentration of less than 0.5 mg/L. Application of standard household water purification devices was recommended for hypothyroidism.