In a cross-sectional study sera of 130 children and adolescents with insulin dependent (type I) diabetes were tested for the presence of cytoplasmatic islet cell antibodies (ICA), thyroid microsomal antibodies (TMA) as well as thyroid function (T3, T4, thyrotrophin). 102 of the patients were examined for thyroid enlargement, all patients with TMA were within this group. TMA were found in 15.4%, ICA in 38.5%, the latter decreasing with duration of diabetes. Of the TMA positive sera, 45% were also ICA positive, but only one child out of these was diabetic for more than 5 years. Thyroid enlargement occurred in 33.3%, however in TMA positive patients in 70%, of which one girl suffered from hypothyroidism due to biopsy-proven Hashimoto's thyroiditis, all the other diabetics being euthyroid. There was no sex predisposition. By HLA-typing 40% of TMA positive patients expressed the HLA-DR3 antigen which is said to be responsible for "autoimmune" diabetes, whereas only some of these were ICA positive as well. In our study, no significant association was found between presence or even persistence of ICA and TMA, nor between thyroid autoimmunity and HLA-DR3. Since type I diabetic patients with thyroid autoimmunity are predisposed to develop hypothyroidism with time, less likely also Addison's disease, screening of type I diabetics for thyroid microsomal antibodies should be considered especially in those with thyroid enlargement.
