Selenium

Selenium's primary mechanism is incorporation into selenoproteins as the rare amino acid selenocysteine (Sec, the 21st amino acid in proteins). Twenty-five selenoproteins are encoded in the human genome, with the most clinically important being: glutathione peroxidases (GPx1-8) which neutralize hydrogen peroxide and lipid peroxides; thioredoxin reductases (TrxR1-3) which maintain redox homeostasis; and iodothyronine deiodinases (DIO1-3) which convert thyroid hormones (T4 to T3 conversion).,The thyroid mechanism is particularly relevant for autoimmune thyroid disease. Selenoproteins protect thyroid follicular cells from peroxide damage during thyroid hormone synthesis - a process that inherently generates reactive oxygen species. In Hashimoto's thyroiditis, selenium supplementation reduces oxidative damage and antibody-mediated destruction, leading to lower TPO antibody titers, improved thyroid function in subclinical hypothyroidism, and reduced inflammation. The deiodinase enzymes also depend on selenium for T4-to-T3 conversion, so deficiency can reduce active thyroid hormone availability.,Beyond thyroid effects, selenium's antioxidant role through GPx and TrxR is broadly cell-protective. Selenium also has direct anti-cancer mechanisms via apoptosis induction in cancer cells (especially methylselenocysteine), heavy metal binding (selenium binds mercury, cadmium, and arsenic, reducing their toxicity), and immune support. The relationship between selenium and cardiovascular disease is U-shaped - both deficiency and excess increase risk.

Selenium's primary mechanism is incorporation into selenoproteins as the rare amino acid selenocysteine (Sec, the 21st amino acid in proteins). Twenty-five selenoproteins are encoded in the human genome, with the most clinically important being: glutathione peroxidases (GPx1-8) which neutralize hydrogen peroxide and lipid peroxides; thioredoxin reductases (TrxR1-3) which maintain redox homeostasis; and iodothyronine deiodinases (DIO1-3) which convert thyroid hormones (T4 to T3 conversion).,The thyroid mechanism is particularly relevant for autoimmune thyroid disease. Selenoproteins protect thyroid follicular cells from peroxide damage during thyroid hormone synthesis - a process that inherently generates reactive oxygen species. In Hashimoto's thyroiditis, selenium supplementation reduces oxidative damage and antibody-mediated destruction, leading to lower TPO antibody titers, improved thyroid function in subclinical hypothyroidism, and reduced inflammation. The deiodinase enzymes also depend on selenium for T4-to-T3 conversion, so deficiency can reduce active thyroid hormone availability.,Beyond thyroid effects, selenium's antioxidant role through GPx and TrxR is broadly cell-protective. Selenium also has direct anti-cancer mechanisms via apoptosis induction in cancer cells (especially methylselenocysteine), heavy metal binding (selenium binds mercury, cadmium, and arsenic, reducing their toxicity), and immune support. The relationship between selenium and cardiovascular disease is U-shaped - both deficiency and excess increase risk.

What's safe to combine, and what belongs in a separate pin.

Storage. Store at room temperature (20-25C) in a cool, dry place. Capsules and tablets shelf-stable for 24+ months. Liquid forms should be refrigerated after opening.

Classified as a dietary supplement in the US. RDA is 55mcg/day for adults. Tolerable Upper Intake Level (UL) is 400mcg/day. Available widely over the counter. Multiple commercial forms (selenomethionine, selenium yeast, sodium selenite, methylselenocysteine).