The expression of GADA, ZnT8A and IA-2A in patients with type 1 diabetes mellitus with thyroid disease and their correlation with thyroid autoantibodies

OBJECTIVE: The aim of this research was to study the expression of anti-glutamate decarboxylase antibody (GADA), zinc transporter-8 autoantibody (ZnT8A), and insulinoma-associated protein-2 antibody (IA-2A) in patients with type 1 diabetes (T1DM) with thyroid disease (TD) and its correlation with thyroid autoantibodies. PATIENTS AND METHODS: 380 patients with T1DM were included in the study, of which 313 patients with T1DM alone were included in the control group. In the TD group, 41 patients with T1DM and Hashimoto's thyroiditis (HT) were included, and 26 cases of T1DM patients with Graves' disease were included in the Graves group. The clinical features of the control group, the HT group, and the Graves group were compared. The positive rates of insulin autoantibodies in the control group and the TD group were analyzed. The clinical characteristics of patients with and without insulin autoantibody positivity were compared. The positive rates of thyroid autoantibodies in T1DM patients with positive GADA, ZnT8A, IA-2A, and different numbers of positive insulin autoantibodies were analyzed. RESULTS: The levels of total cholesterol (TC) and thyroid stimulating hormone (TSH) in the HT group were significantly higher than those in the control and Graves groups, and the levels of free thyroid hormone (FT4) and low-density lipoprotein cholesterol (LDL-C) were significantly lower than those in the control and Graves groups (p<0.001). The levels of TC and TSH in the Graves group were significantly lower than those in the control group, the levels of HbA1c, LDL-C, and FT4 were significantly higher than those in the control group, and the levels of FT3 were significantly higher than those in the control and HT groups (p<0.001). The levels of C peptide, triglyceride (TG), and LDL-C of insulin autoantibodies positive patients were significantly lower than those of negative patients (p<0.05). The positive rates of GADA, ZnT8A, and IA-2A in the TD group, as well as the positive rates of double antibodies and triple antibodies, were significantly higher than those of the control group (p<0.05). In T1DM patients, the positive rates of thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TGAb) in GADA and IA-2A-positive patients were significantly higher than those in GADA and IA-2A-negative patients (p<0.05). The positive rate of TPOAb in ZnT8A-positive patients was significantly higher than that in ZnT8A-negative patients (p<0.05). The positive rates of TRAb, TPOAb, and TGAb in T1DM patients positive for two of the three insulin autoantibodies and three insulin autoantibodies were significantly higher than those positive for one of the three insulin autoantibodies (p<0.001). CONCLUSIONS: TD can exacerbate the disorder of glucose and lipid metabolism in patients with T1DM, and multiple insulin autoantibodies positive T1DM patients it is more likely to have thyroid autoantibody positivity. It is suggested that patients with aggravated glucose and lipid metabolism and multiple insulin autoantibody positivity should be routinely screened for thyroid antibodies to help early diagnosis of TD.