Se is primarily stored in the body as selenoprotein that plays a crucial role in the immune system and activation of thyroid hormones.[13,14] In patients with autoimmune thyroid diseases, the Se levels are significantly low, leading to weakened resistance against oxidative stress.[15] The synthesis of thyroid hormone requires the enzyme thyroid peroxidase (TPO) to convert iodine into active iodine, which then iodinates tyrosine residues under the oxidation of hydrogen peroxide (H2O2). The gene discussed is TG; the disease is autoimmune thyroid disease.