Selenium:
high amounts of iodine without selenium induces AIT (Auto Immune Thyroiditis) and goiter.
selenium + iodine reduces goiter and inflammation of the thyroid gland.
selenium supplementation reduces TgAb that may be elevated by taking iodine.
TPOAb antibody levels were inversely associated with selenium levels (if you have high selenium, you have low antibodies and vice versa).
selenium + iodine increases the regulatory immune cells which prevent the development of autoimmune diseases.
necessary for the body to produce glutathione peroxidase, which detoxes pesticides, mercury, chlorine and bromide.
Analysis of the medical literature is clear:
selenium plus iodine is the best combination for thyroid health. When iodine has been shown in studies to be damaging to the thyroid, it appears that concurrent selenium deficiency is the true culprit.
Not only that, if you are iodine deficient, selenium supplements “induce a dramatic fall of the already impaired thyroid function in clinically hypothyroid subjects”.
Effect of selenium supplementation in hypothyroid subjects of an iodine and selenium deficient area: the possible danger of indiscriminate suppleme... - PubMed - NCBI
Therefore, if you are already hypothyroid, taking selenium supplements while iodine deficient will make you MORE HYPOTHYROID.