Autoimmunity is characterized by an impaired self-tolerance and is the major cause for the two common autoimmune thyroid diseases (AITD), Hashimoto’s thyroiditis (HT), and Graves’ disease (GD) (Taylor et al. 2018). In AITD, the autoantibodies (aAb) to thyroglobulin (Tg), thyroperoxidase (TPO), and TSH receptor (TSH-R), respectively, are characteristic diagnostic markers. The thyroid gland is rich in the trace element selenium (Se), which may modulate the endocrine-immune interface and affect hydrogen peroxide metabolism, inflammation, and aAb generation (Duntas et al. 2015, Wu et al. 2015). Selenium transport is mediated by selenoprotein P (SELENOP) (Burk et al. 2015), and low Se supply is known to increase HT risk (Schomburg et al. 2011). In this study we hypothesize that autoimmunity to SELENOP may be associated with AITD.