ArticleEnvironment international2024
Fluoride exposure and thyroid hormone levels in pregnancy: The MIREC cohort.
Article in Environment international, 2024. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 6 papers.
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Who cites it
6 citing papers in PubMed, 11 citations in OpenAlex.
- Prenatal fluoride exposure and pregnancy outcomes in two US pregnancy cohorts.International journal of epidemiology · 2026Article
- International fluoride symposium: effects of fluoride on human health and its mechanisms of action - a meeting report.BMC proceedings · 2025Article
- Updated consumer risk assessment of fluoride in food and drinking water including the contribution from other sources of oral exposure.EFSA journal. European Food Safety Authority · 2025Article
- Fluoride, Teeth, and Developing Brains: Dental Health in Tension With Environmental Health, Millions Affected.American journal of public health · 2025Article
- How the public's knowledge, attitudes, and practice intersect with scientific evidence about fluoride.Current problems in pediatric and adolescent health care · 2025Article
- Article
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Authors and funding
6 authors at 4 institutions in 1 country.
Funding
Abstract
backgroundFluoride exposure may increase the risk of hypothyroidism, but results from previous studies are inconsistent at low-level fluoride exposure (i.e., ≤0.7 mg/L). Human studies of fluoride and thyroid hormone levels in pregnancy are scarce.
objectivesWe examined associations between fluoride exposure and maternal thyroid hormone levels in a Canadian pregnancy cohort, with consideration for fetal sex-specific effects.
methodsWe measured fluoride concentrations in drinking water and spot urine samples collected during each trimester from 1876 pregnant women enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) study. We also measured maternal thyroid stimulating hormone (TSH), free thyroxine (FT4), and total thyroxine (TT4) levels during the first trimester of pregnancy. We used linear and non-linear regression models to estimate associations between fluoride exposure and levels of TSH, FT4, and TT4. We explored effect modification by fetal sex and considered maternal iodine status as a potential confounder.
resultsA 1 mg/L increase in urinary fluoride was associated with a 0.30 (95 %CI: 0.08, 0.51) logarithmic unit (i.e., 35.0 %) increase in TSH among women pregnant with females, but not males (B = 0.02; 95 %CI: -0.16, 0.19). Relative to women with urinary fluoride concentrations in the first quartile (0.05-0.32 mg/L), those with levels in the third quartile (0.49-0.75 mg/L) had higher FT4 and TT4 (i.e., inverted J-shaped associations), but the association was not statistically significant after adjustment for covariates (p = 0.06). Water fluoride concentration showed a U-shaped association with maternal FT4, whereby women with water fluoride concentrations in the second (0.13-0.52 mg/L) and third (0.52-0.62 mg/L) quartiles had significantly lower FT4 compared to those with levels in the first quartile (0.04-0.13 mg/L). Adjustment for maternal iodine status did not change the results. DISCUSSION: Fluoride exposure was associated with alterations in maternal thyroid hormone levels, the magnitude of which appeared to vary by fetal sex. Given the importance of maternal thyroid hormones for fetal neurodevelopment, replication of findings is warranted.
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