Evidence that type I diabetes and thyrogastric autoimmunity have different genetic determinants.

The prevalences of autoimmune endocrine disease and relevant organ-specific autoantibodies were determined in 141 patients with type I (insulin-dependent) diabetes and their families. All available members of the families were genotyped for HLA. Islet-cell antibody was found in 10 (4%) out of 248 unaffected siblings, all of whom were genetically potential cases of diabetes. One developed classical symptoms six months later. In contrast, thyroid and gastric parietal-cell antibodies occurred independent of the HLA-linked susceptibility to diabetes. These results suggest that different genes control the production of these autoantibodies and the susceptibility to type I diabetes.