The Study
Iodine Modifies the Susceptibility of Thyroid to Fluoride Exposure in School-age Children: a Cross-sectional Study in Yellow River Basin, Henan, China
This study looked at a group of kids and found that those with more fluoride in their urine tended to have bigger thyroids, and kids with more iodine seemed to have less of a change. But it didn’t change anything on purpose — it just watched what was already happening, so we can’t say fluoride made the thyroids bigger or iodine fixed it.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
Fluoride in water or tea can make kids' thyroids grow bigger, especially in boys. But if they have enough iodine (from salt or food), their thyroids don't grow as much.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 544 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1A 0.22 cm³ increase is small but measurable; in children, even small thyroid changes can signal early disruption, especially if hormone levels drop.
- 2Every time fluoride in urine went up by one standard deviation, thyroid size increased by 0.22 cm³.
- 3Boys' thyroids grew more than girls'.
- 4With iodine ≤300 μg/L, higher fluoride meant lower TT3 hormone.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Biological Trace Element Research
Year
2021
Authors
Yuhui Du, Guoyu Zhou, Biao Gong, Jun Ma, Ning An, Minghui Gao, Meng Yang, Qiang Ma, Hui Huang, Q. Zuo, Y. Ba
Related Content
Claims (5)
Boys' thyroids tend to get bigger than girls' when they're exposed to fluoride in water or food, which suggests boys might be more sensitive to fluoride's effects on their thyroid gland.
When kids have just enough iodine in their urine but are exposed to more fluoride, their bodies might make less of an important thyroid hormone called TT3 — like their thyroid is struggling a bit under those conditions.
In kids aged 7 to 12, the more fluoride they have in their urine, the bigger their thyroid gland tends to be — by a tiny amount, about the size of a small grape.
When kids have more iodine in their urine, fluoride doesn’t seem to make their thyroid gland grow as much—so iodine might help protect their thyroid from fluoride’s effects.
In kids, more fluoride in their urine seems to be linked to bigger thyroids, but iodine in their urine doesn’t seem to make a clear difference—so fluoride might be the main thing affecting their thyroid size.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.