The Study
Association of Mild-to-Moderate Iodine Deficiency With Thyroid Function—A Systematic Review and Meta-analysis
This study looked at many other studies that measured iodine levels and thyroid hormones in people. It found that having slightly low iodine doesn’t clearly change thyroid hormone levels. But because these studies just took a snapshot in time, we can’t say for sure whether low iodine causes changes or not.
Analysis score
Maximum 100 for a systematic review with meta-analysis.
Where the score came from
This study looked at whether people who don’t have quite enough iodine in their body have problems with their thyroid, which helps control energy and growth.
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 546 / 100
Quality score
The highest quality evidence. Systematic reviews and meta-analyses that pool randomized controlled trials, giving the most reliable summary of experimental evidence.
Key takeaways
Summary
Based on the study abstract and findings.
- 1These tiny changes don’t matter for how the body works — like finding one less jellybean in a jar and still having plenty.
- 2In pregnant women, the difference in thyroid hormone levels was tiny: TSH changed by just 0.03, fT4 by -0.20, and fT3 by 0.05 — all within normal ranges.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Advances in Nutrition
Year
2025
Authors
Tonje E. Aarsland, Inger Aakre, T. H. Stea, S. Henjum, M. Markhus, T. Strand, Lisbeth Dahl, Tim I M Korevaar, K. S. Bakken, S. Sleire
Related Content
Claims (6)
Pregnant women with slightly low iodine levels don’t seem to have noticeable changes in their thyroid hormones compared to those with good iodine levels — their thyroid still works fine even if their iodine isn’t perfect.
For kids, teens, and adults, not getting quite enough iodine doesn’t seem to clearly affect thyroid hormone levels — some studies see no change, others see mixed results, so we can’t say for sure either way.
We don't have strong enough proof to say whether mild or moderate iodine deficiency really affects thyroid function, because the studies done so far aren't very reliable or consistent.
People who don’t get quite enough iodine don’t seem to have a clear difference in thyroid problems compared to those who get enough — most studies show no big link, even though a few suggest there might be a small risk.
Your thyroid can still work normally even if you're not getting quite enough iodine, thanks to built-in backup systems that kick in for months or years.
Your body uses iodine to build thyroid hormones — without iodine, it can't make the key hormones that help control your metabolism.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.