Diffuse hyperthyroidism (Graves disease) is a disease caused by many factors and genetic susceptivity may play a key role in pathogenesis of Graves disease. As a susceptibility gene for many autoimmune diseases, protein tyrosine phosphatase non-receptor type 22 (PTPN22) plays negative regulation of T-cell signal transduction and in maintaining the immune system balance through encoding lymphoid tyrosine phosphatase (LYP), PTPN22 gene polymorphism (C1858T) leads to the decrease in T cell surface receptors (TCR) signaling and the functional defection in the regulatory T cells (Tregs), subsequently results in Graves disease.