Karanikas et al. (2005) have shown that a high titer of TPOAb may significantly contribute to increased TNF-α production, which is associated with high activity of Hashimoto thyroiditis. Therefore, we suggest that a disturbance of intestinal microflora components, such as Prevotella and Bacteroides, can affect the Th1/Th2 balance and related cytokines, and an increase in the levels of cytokines, such as TNF-α and IFN-γ, can cause thyroid injury via various pathways. This evidence concerns the gene IFNG and Hashimoto thyroiditis.