Psychology Department, York University, Toronto, ON, Canada.
Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada.
Sci Total Environ. 2023 Apr 15;869:161149. doi: 10.1016/j.scitotenv.2022.161149. Epub 2023 Feb 9.
While fluoride can have thyroid-disrupting effects, associations between low-level fluoride exposure and thyroid conditions remain unclear, especially during pregnancy when insufficient thyroid hormones can adversely impact offspring development.
We evaluated associations between fluoride exposure and hypothyroidism in a Canadian pregnancy cohort.
We measured fluoride concentrations in drinking water and three dilution-corrected urine samples and estimated fluoride intake based on self-reported beverage consumption. We classified women enrolled in the Maternal-Infant Research on Environmental Chemicals Study as euthyroid (n = 1301), subclinical hypothyroid (n = 100) or primary hypothyroid (n = 107) based on their thyroid hormone levels in trimester one. We used multinomial logistic regression to estimate the association between fluoride exposure and classification of either subclinical or primary hypothyroidism and considered maternal thyroid peroxidase antibody (TPOAb) status, a marker of autoimmune hypothyroidism, as an effect modifier. In a subsample of 466 mother-child pairs, we used linear regression to explore the association between maternal hypothyroidism and child Full-Scale IQ (FSIQ) at ages 3-to-4 years and tested for effect modification by child sex.
A 0.5 mg/L increase in drinking water fluoride concentration was associated with a 1.65 (95 % confidence interval [CI]: 1.04, 2.60) increased odds of primary hypothyroidism. In contrast, we did not find a significant association between urinary fluoride (adjusted odds ratio [aOR]: 1.00; 95%CI: 0.73, 1.39) or fluoride intake (aOR: 1.25; 95%CI: 0.99, 1.57) and hypothyroidism. Among women with normal TPOAb levels, the risk of primary hypothyroidism increased with both increasing water fluoride and fluoride intake (aOR water fluoride concentration: 2.85; 95%CI: 1.25, 6.50; aOR fluoride intake: 1.75; 95%CI: 1.27, 2.41). Children born to women with primary hypothyroidism had lower FSIQ scores compared to children of euthyroid women, especially among boys (B coefficient: -8.42; 95 % CI: -15.33, -1.50).
Fluoride in drinking water was associated with increased risk of hypothyroidism in pregnant women. Thyroid disruption may contribute to developmental neurotoxicity of fluoride.
尽管氟化物会对甲状腺产生干扰作用，但低水平氟化物暴露与甲状腺疾病之间的关联仍不清楚，尤其是在怀孕期间，此时甲状腺激素不足会对后代发育产生不利影响。
我们评估了加拿大妊娠队列中氟化物暴露与甲状腺功能减退症之间的关联。
我们测量了饮用水和三种经稀释校正的尿液样本中的氟化物浓度，并根据自我报告的饮料摄入量估算了氟化物摄入量。我们根据第一孕期的甲状腺激素水平，将参与母婴环境化学物质研究的妇女分为甲状腺功能正常（n=1301）、亚临床甲状腺功能减退（n=100）或原发性甲状腺功能减退（n=107）。我们使用多变量逻辑回归估计氟化物暴露与亚临床或原发性甲状腺功能减退分类之间的关联，并考虑了甲状腺过氧化物酶抗体（TPOAb）状况，这是自身免疫性甲状腺功能减退的标志物，作为效应修饰剂。在 466 对母婴样本中，我们使用线性回归探讨了母体甲状腺功能减退症与儿童在 3 至 4 岁时的全量表智商（FSIQ）之间的关联，并检验了儿童性别对效应的修饰作用。
饮用水中氟化物浓度每增加 0.5mg/L，原发性甲状腺功能减退症的发生几率就会增加 1.65 倍（95%置信区间[CI]：1.04，2.60）。相比之下，我们没有发现尿氟化物（调整后的比值比[aOR]：1.00；95%CI：0.73，1.39）或氟化物摄入量（aOR：1.25；95%CI：0.99，1.57）与甲状腺功能减退症之间存在显著关联。在 TPOAb 水平正常的女性中，随着饮用水中氟化物和氟化物摄入量的增加，原发性甲状腺功能减退症的风险也随之增加（水氟浓度的 aOR：2.85；95%CI：1.25，6.50；氟化物摄入量的 aOR：1.75；95%CI：1.27，2.41）。与甲状腺功能正常的女性所生的孩子相比，患有原发性甲状腺功能减退症的女性的孩子的 FSIQ 得分较低，尤其是男孩（B 系数：-8.42；95%CI：-15.33，-1.50）。
饮用水中的氟化物与孕妇甲状腺功能减退症的风险增加有关。甲状腺功能紊乱可能是氟化物发育神经毒性的原因之一。
