Most cases of hypothyroidism occur because the immune system attacks the thyroid gland, and the thyroid naturally holds more selenium than most other tissues in the body.
Evidence from Studies
Supporting (3)
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Selenium supplementation and placebo are equally effective in improving quality of life in patients with hypothyroidism
This study shows that selenium helps reduce immune attacks on the thyroid in people with autoimmune hypothyroidism, which supports the idea that selenium plays an important role in thyroid health. It doesn't prove selenium is concentrated there, but it strongly suggests selenium is involved in how the thyroid gets damaged.
Concentration of Metals and Trace Elements in the Normal Human and Rat Thyroid: Comparison with Muscle and Adipose Tissue and Volcanic Versus Control Areas
This study found that selenium, a mineral, is packed much more tightly in the thyroid gland than in other parts of the body like muscle or fat — which matches part of the claim. But it didn’t look at why most hypothyroidism happens.
This study found that selenium, a mineral, is packed tightly in the thyroid gland — which matches what the claim says. It doesn't prove that 90% of thyroid problems are from the immune system attacking the gland, but it does show selenium is important there, which fits with the rest of the claim.
Contradicting (0)
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Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.