The aim of the present study was to investigate the role of the rs1990760 polymorphism within the IFIH1 gene in German patients with GD (n = 258), Hashimoto's thyroiditis (HT, n = 106), Addison's disease (AD, n = 195) and healthy controls (HC, n = 227) as well as in 55 GD families (165 individuals, German) and 100 HT families (300 individuals, Italian). Here, IFIH1 is linked to Hashimoto thyroiditis.