Frequency of diabetes and thyroid autoantibodies in patients with type 1 diabetes and their siblings

Abstract

The aim of this study was to better understand the frequency of autoimmune thyroid and diabetes antibodies in patients with type 1 diabetes mellitus (T1DM) compared with their siblings. Glutamic acid decarboxylase antibodies (GADA), islet cell antibodies (ICA), insulin autoantibodies (IAA), and thyroid autoantibodies were studied in all subjects. The rates of positive GADA and IAA were significantly higher in probands compared to in siblings (p＜0.001) or controls (p＜0.001). All pancreatic autoantibodies were not significantly different between the siblings and the healthy controls. Thyroid antiperoxidase antibody (TPOAb) and antithyroglobulin antibody (TGAb) were significantly different between the probands and the control subjects (p=0.002 and p=0.018, respectively). The rates of TPOAb and TGAb positivity in siblings were higher than in those of the controls, but there was no significant difference between the two groups. However, thyroid autoimmunity (TA) was significantly different among the groups (p=0.004). Siblings of the TA-positive probands were shown to have a greater prevalence of thyroid antibodies than did the controls (p=0.022), but siblings of the TA-negative probands did not have such a prevalence compared with the control subjects. The prevalence of pancreatic and thyroid antibodies positivity in probands was statistically significant compared with the siblings and the controls. Siblings of TA-positive probands revealed a greater prevalence of thyroid antibodies than did the controls. Therefore, the screening for TA in siblings, particularly siblings of TA-positive probands, is as important as it is in probands. INTRODUCTIONType 1 diabetes mellitus (T1DM) results from lack of insulin secretion caused by the destruction of pancreatic  cells.1 Most patients with T1DM have the diabetes autoantibodies such as insulin autoantibodies (IAA), glutamic acid decarboxylase (GADA), and islet cell antibody (ICA). 2T1DM patients are at an increased risk for additional autoimmune diseases like that Graves' disease, Hashimoto's thyroiditis, and Addison's disease. 3 The most common autoimmune disorder related with T1DM is autoimmune thyroid disease (AIT). [4][5][6][7] The frequency of thyroid autoantibody positivity in children with T1DM has been reported in about 50% in different ethnicity.8 Thyroid disorders occurred within 3 to 4 years in fifty percent of the thyroid autoantibody positive subjects. 5,9 It has been suggested that T1DM and AIT have common genetic sources since they often co-occur in patients and families. 10 The risk for this autoimmune disorder is known to increase in first-degree relatives of T1DM subjects, and 8% of first-degree families have AIT. 11,12 To our best knowledge, the frequency of autoantibodies for diabetes and thyroid in Korean children with T1DM and their siblings have not been investigated. So, in this study, we aim to investigate the frequency of autoimmune thyroid and diabetes antibodies in patients of T1DM, their siblings, and healthy controls. MATERIALS AND METHODS Su...