Increased frequency of subclinical hypothyroidism and thyroid associated antibodies in siblings of children and adolescents with type 1 diabetes mellitus

In recent years, it has been well established that early detection of thyroid autoimmunity or disease in children is important, leading to the idea of treating patients with subclinical hypothyroidism in the presence of high serum thyroid antibody, as progression to overt hypothyroidism is common (1). Furthermore, thyroxine replacement therapy started early in patients with subclinical hypothyroidism reduces the risk of hyperlipidemia and atherosclerotic heart disease (2). Disease-associated autoantibodies can be easily used as a tool to identify patients at increased risk of progression to clinical thyroid dysfunction. Because siblings of patients with type 1 diabetes mellitus (T1DM) share the HLA-risk alleles, we asked whether they might be at increased risk of thyroid autoimmunity and disease.