Iodine Modifies the Susceptibility of Thyroid to Fluoride Exposure in School-age Children: a Cross-sectional Study in Yellow River Basin, Henan, China

Du, Yuhui; Zhou, Guoyu; Gong, Biao; Ma, Jun; An, Ning; Gao, Minghui; Yang, Meng; Ma, Qiang; Huang, Hui; Zuo, Qiting; Ba, Yue

doi:10.1007/s12011-020-02519-8

Cited by 9 publications

(7 citation statements)

References 44 publications

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“…We found that the association between prenatal fluoride exposure and FSIQ was stronger among boys whose mothers had low urinary iodine concentrations in pregnancy compared to boys whose mothers had adequate iodine concentrations in pregnancy. These findings are consistent with previous experimental and human epidemiological studies [27][28][29][30]45] and indicate that even mildly reduced iodine levels may have biological significance when interacting with fluoride. Importantly, our findings were observed in a Canadian pregnancy sample with, on average, sufficient iodine intake (median iodine = 294 µg/g) and with 88% of women taking prenatal multi-vitamins.…”

Section: Discussionsupporting

confidence: 93%

“…In our study, the interaction between fluoride and iodine was only evident in boys. This finding is consistent with a recent cross-sectional study conducted in China showing that iodine modified the susceptibility of the thyroid gland to fluoride exposure in school-aged boys, but not girls [ 45 ]. For boys with lower urinary levels of iodine, higher urinary fluoride was associated with larger thyroid volumes, whereas higher levels of iodine reduced the effects of fluoride on the thyroid.…”

Section: Discussionsupporting

confidence: 92%

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Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys’ Intelligence

et al. 2022

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In animal studies, the combination of in utero fluoride exposure and low iodine has greater negative effects on offspring learning and memory than either alone, but this has not been studied in children. We evaluated whether the maternal urinary iodine concentration (MUIC) modifies the association between maternal urinary fluoride (MUF) and boys’ and girls’ intelligence. We used data from 366 mother–child dyads in the Maternal–Infant Research on Environmental Chemicals Study. We corrected trimester-specific MUF and MUIC for creatinine, and averaged them to yield our exposure variables (MUFCRE, mg/g; MUICCRE, µg/g). We assessed children’s full-scale intelligence (FSIQ) at 3 to 4 years. Using multiple linear regression, we estimated a three-way interaction between MUFCRE, MUICCRE, and child sex on FSIQ, controlling for covariates. The MUICCRE by MUFCRE interaction was significant for boys (p = 0.042), but not girls (p = 0.190). For boys whose mothers had low iodine, a 0.5 mg/g increase in MUFCRE was associated with a 4.65-point lower FSIQ score (95% CI: −7.67, −1.62). For boys whose mothers had adequate iodine, a 0.5 mg/g increase in MUFCRE was associated with a 2.95-point lower FSIQ score (95% CI: −4.77, −1.13). These results suggest adequate iodine intake during pregnancy may minimize fluoride’s neurotoxicity in boys.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 92%

Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys’ Intelligence

et al. 2022

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“…TSH receptor inactivation can result in decreased thyroid hormone production in the thyroid gland. These effects can be the reasons for the thyroid hormone feedback loop to attain new equivalence, resulting in increased TSH levels [ 18 , 60 , 61 ]. Fluoride additionally inhibits pathways that are indirectly a part of this TSH feedback loop, as described in the following.…”

Section: Discussionmentioning

confidence: 99%

Iodine Status in Pregnant Women Having Urinary Fluoride in Contaminated Areas: A Case Study of Phayao Province

Somporn

Lapinee

Umponstira

et al. 2023

Journal of Environmental and Public Health

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Fluoride naturally occurs in the Earth’s crust and is widely dispersed in groundwater. The high consumption of fluoride can inhibit iodine metabolism in the human body, especially in the thyroid gland. This study assessed iodine knowledge, iodine consumption behavior, urinary iodine (UI), thyroid stimulating hormone (serum TSH), and free triiodothyronine3 (serum FT3) and examined the connection between fluoride exposure and UI and thyroid function as serum concentrations of TSH and FT3 in pregnant women dwelling in an area of endemic fluorosis. This was a cross-sectional study. The population included 152 pregnant women within the 1st trimester of pregnancy, during which they were provided antenatal care (ANC) in seven public community hospitals in Phayao province, Thailand. The study consisted of two components. First, the study consisted of a questionnaire in which we evaluated the iodine knowledge and iodine consumptive behaviors in subjects. Second, biochemical data were investigated to evaluate thyroid function in the subjects. The gestational age of most subjects was 8–12 weeks. The study population has lived in fluoride-contaminated areas since birth (76.97%). The iodine and iodine consumption levels were moderate (50.00%). Their food iodine consumption was 3–4 days/week, and the top five consumption ranks were iodized salt, cooked pork, eggs, sticky rice, and iodine fish sauce. In terms of biochemical parameters, 63.16% of respondents had UI levels below 150.00 g/L, which is below the normal reference range of 150.00–249.00 g/L. 89.47% of the risk of hypothyroidism was associated with serum TSH levels below 2.50 g/L. In 38.16% of the samples, normal levels of serum FT3 (2.00–4.40 pg/L) were identified in the subjects. In addition, 61.84% of the samples had FT3 concentrations greater than 4.40 pg/L (high intake of iodine). The approved association between positive serum FT3 data and serum TSH was positive (r = 260 and p < 0.05). These studies imply that these elevated levels of TSH and FT3 place pregnant women in their first trimester at risk for hypothyroidism.

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“…Children and adolescents who are I sufficient but living in areas with high concentrations of water F had higher rates of endemic goiter than those living in areas with low concentrations of water F [ 23 ]. Another recent study found smaller thyroid volume in children with high UIC than those with low UIC who were living in a high environmental F area of China [ 152 ]. Thyroid volume increased with increasing UFC with a greater change observed in boys than in girls [ 152 ].…”

Section: And F and Thyroid Functionmentioning

confidence: 99%

“…Another recent study found smaller thyroid volume in children with high UIC than those with low UIC who were living in a high environmental F area of China [ 152 ]. Thyroid volume increased with increasing UFC with a greater change observed in boys than in girls [ 152 ]. Total T3 was negatively associated with UFC in those with UIC ≤300 μg/L [ 152 ].…”

Section: And F and Thyroid Functionmentioning

confidence: 99%

A Scoping Review of Iodine and Fluoride in Pregnancy in Relation to Maternal Thyroid Function and Offspring Neurodevelopment

Griebel-Thompson¹,

Sands²,

Chollet‐Hinton³

et al. 2023

Advances in Nutrition

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Iodine Modifies the Susceptibility of Thyroid to Fluoride Exposure in School-age Children: a Cross-sectional Study in Yellow River Basin, Henan, China

Cited by 9 publications

References 44 publications

Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys’ Intelligence

Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys’ Intelligence

Iodine Status in Pregnant Women Having Urinary Fluoride in Contaminated Areas: A Case Study of Phayao Province

A Scoping Review of Iodine and Fluoride in Pregnancy in Relation to Maternal Thyroid Function and Offspring Neurodevelopment

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