The Study
Thyroid function in patients with selenium deficiency exhibits high free T4 to T3 ratio
This study looked at a small group of kids and adults who didn't get enough selenium and noticed their thyroid numbers looked different. But it didn't prove that selenium caused those changes — maybe other things like their illnesses or medicines did. It's like noticing people who eat a lot of candy also have more cavities — but that doesn't mean candy always causes cavities.
Analysis score
Maximum 58 for a case-control study.
Where the score came from
Your body needs selenium to turn the inactive thyroid hormone (T4) into the active one (T3). If you don't get enough selenium, this conversion slows down, making T4 build up and T3 drop.
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
Researchers compare people who have a condition (cases) with similar people who do not (controls), looking back in time for differences in exposure. Useful but more prone to bias.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — this means low selenium can cause thyroid hormone imbalance without making your thyroid gland sick, and it can be fixed by eating more selenium-rich foods or taking supplements.
- 2In selenium-deficient patients, 27% had low T3, and the T4/T3 ratio was much higher than in healthy people.
- 3After taking selenium supplements, T3 went up and the ratio went down.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Clinical Pediatric Endocrinology
Year
2021
Authors
Ryohei Kobayashi, M. Hasegawa, C. Kawaguchi, N. Ishikawa, K. Tomiwa, M. Shima, K. Nogami
Related Content
Claims (10)
The body converts the thyroid hormone T4 into its active form, T3, using enzymes that require selenium as a component.
Selenium is necessary for the body to convert the thyroid hormone T4 into its active form, T3, and changes in the genes that code for deiodinase enzymes reduce this conversion.
The thyroid hormone T4 is changed into a more active form called T3 in organs like the liver and kidneys through a biochemical process.
In people with low selenium levels from limited food intake or nutritional support, a specific blood ratio of thyroid hormones (free T4 to free T3) is higher than in people with normal selenium levels, which may help detect selenium deficiency before symptoms appear.
In people with low selenium levels, the ratio of two thyroid hormones (FT4 to FT3) tends to rise more reliably than the individual levels of those hormones, making it a better marker for detecting disruptions in how the body processes thyroid hormones than measuring TSH, FT4, or FT3 by themselves.
In people with low selenium levels, taking selenium supplements lowers free T4 and the ratio of free T4 to free T3 while raising free T3 levels, suggesting that selenium plays a role in how the body converts thyroid hormones and that this process can improve with supplementation.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.