Humoral immune abnormalities in diabetes mellitus.

We previously showed that for Singapore diabetics, a low prevalence of islet cell antibodies (ICA) and insulin autoantibodies (IAA) were observed, unlike the high prevalence rates in Caucasian populations. In this report, we have measured other autoimmune markers (thyroid autoantibodies, thyrotrophin [TSH] receptor antibodies, rheumatoid factor and anti-dsDNA antibodies) to assess the extent of autoimmunity in our newly diagnosed diabetes patients and those with long-standing diabetes. Results indicate that there is a raised prevalence of thyroid autoantibodies in diabetics compared to the general population. Thyroid autoantibodies occurred in 24.3% (28/115) of the patients; thyroid microsomal antibodies (16.5%, 19/115) was much higher than for thyroglobulin antibodies (1.7%, 2/115). Prevalence rates of thyroid autoantibodies were lower in diabetics who were newly diagnosed (21.6%, 11/51), compared to those with long-standing disease (25.5%, 14/55). Three patients (3/9) with gestational diabetes were also positive for thyroid autoantibodies. TSH receptor antibodies associated with Graves' disease, were found in two patients. However, they also had thyrotoxicosis. Five patients (4.3%, 5/115) were detected with rheumatoid factor, but were clinically asymptomatic. Anti-dsDNA antibodies were not detected in any of the subjects. The presentation of thyroid autoantibodies or rheumatoid factor with age did not coincide with diabetes-associated ICA and IAA. It may mean that inspite of prevalence of subclinical autoimmunity in diabetes, autoimmunity against beta-cell lesions is not associated with the overall autoimmune tendency in our diabetes.