The aim of this study was to determine the prevalence of autoantibody biomarkers including GADA, IAA, IA-2A and ZnT8A in type 1 diabetes (T1D), tissue transglutaminase autoantibodies (tTGA) in celiac disease (CD) and thyroid peroxidase autoantibodies (TPOA) in autoimmune thyroid disease (AITD) in individuals, living in three Swedish regions, and diagnosed with T2D, and compare them to T1D individuals as well as to population-based controls. The gene discussed is TPO; the disease is type 1 diabetes mellitus.