Selenium — Thyroid + Antioxidant Cofactor
Selenoproteins help convert thyroid T4 to active T3 and protect the thyroid. Deficiency is rare in the US, and Brazil nuts are high enough to exceed the upper limit.
Selenium is an essential trace mineral whose selenoproteins help convert the thyroid prohormone T4 into active T3 and help protect the thyroid gland — the blood test shows your selenium status against your lab's range.
The biomarker
- Name: Serum Selenium
- Units: µg/L (some labs report µg/dL — multiply by 10 to convert to µg/L)
- Standard reference range: laboratory-specific — read your result against the range printed on your report (ranges vary by lab)
How to read your result
| Value | Interpretation |
|---|---|
| Below your lab's range | Ask your clinician to review your diet; selenium deficiency is rare in the United States |
| Within your lab's range | No action suggested by this result alone |
| Above your lab's range | Chronically high intake causes selenosis — review all selenium sources with your clinician and do not keep taking selenium supplements without their advice |
What to know about intake
- Food sources. Brazil nuts, fish, shellfish, red meat, grains, eggs and chicken all provide selenium. The adult RDA is 55 mcg a day.
- Brazil nuts. One nut carries 68–91 mcg of selenium, so eating many can push intake past the 400 mcg adult upper limit.
- Supplements. Do not start selenium supplements without a clinician, and avoid stacking several products that each contain selenium.
- Testing. Recheck only if your clinician advises it.
Why this test is worth asking for
- The thyroid holds more selenium than any other organ, and selenoproteins are needed to convert T4 to the active hormone T3.
- The selenoproteins glutathione peroxidase and thioredoxin reductase help protect the thyroid from the hydrogen peroxide made during hormone synthesis.
- Selenium is not part of standard metabolic panels, so it has to be requested — often discussed alongside a TSH / free T3 / T4 panel.
Related protocols
- TSH, Free T3 and T4 — Thyroid Panel
- Magnesium RBC — Cellular Magnesium Status Explained
- Zinc — Immune Mineral Status
Sources
AgeGen lab guides are educational only. We do not provide medical diagnosis, prescribe brands, or recommend specific doses. Talk to a licensed clinician before changing your supplement or medication routine.
