Effect of antithyroid autoantibodies on pancreatic islet-cell function

Association of Autoimmune Thyroid Disease with Anti-GAD Antibody ELISA Test Positivity and Risk for Insulin Deficiency in Slowly Progressive Type 1 Diabetes

The presence of antiglutamic acid decarboxylase antibody (GADA) is required for the diagnosis of slowly progressive type 1 diabetes (SPT1D). We examined the factors influencing GADA determination by radioimmunoassay (GADA-RIA) and by enzyme-linked immunosorbent assay (GADA-ELISA). Sixty patients with SPT1D and 154 patients with type 2 diabetes were examined by both GADA-RIA and GADA-ELISA and for the presence of autoimmune thyroid disease (AITD). We compared the clinical characteristics of these patients based on the positivity or negativity of GADA-RIA and GADA-ELISA, and the existence or nonexistence of AITD. Thirty of 60 (50.0%) GADA-RIA-positive patients were GADA-ELISA negative, whereas none of the 154 GADA-RIA-negative patients were GADA-ELISA positive. Concomitant AITD was significantly less in patients with GADA-RIA and without GADA-ELISA and was significantly more in patients with GADA-RIA and GADA-ELISA. In GADA-RIA-positive patients, there was no significant difference in the GADA-RIA titer among the GADA-ELISA-negative patients with and without AITD, and the GADA-ELISA-positive patients without AITD; whereas the frequency of insulin deficiency was significantly higher in the patients with AITD and/or GADA-ELISA than in those without AITD and GADA-ELISA. Examination of GADA-ELISA and AITD in GADA-RIA-positive patients might be useful in predicting insulin deficiency in these patients.

Thyroid autoantibodies and thyroid function in patients with pancreatic adenocarcinoma

Pancreatic adenocarcinoma (PA) patients often present high serum titres of several autoantibodies including autoantibodies against beta-islet cells and insulin. In the present study we examined with an hemagglutination method the sera of 33 patients with PA for the presence of both anti-mitochondrial and anti-thyroglobulin antithyroid autoantibodies (ATA). Twenty-six surgical patients with other non-malignant gastrointestinal tract (GI) disease (chronic pancreatitis or hernia) and 40 healthy volunteers were used as controls. Eight of the 33 PA patients were found to have ATA autoantibodies, whereas only one patient with chronic pancreatitis and 2 normal individuals had high serum ATA titres. The difference between the PA patients and either of the control groups was statistically significant (p < 0.05). The production of autoantibodies could be attributed to impaired immunoregulation caused by the malignant cells.