Relative Frequency of Islet Autoimmunity in Children and Adolescents with Autoimmune Thyroid Disease.

The present study aims to investigate islet autoimmunity and susceptibility to type 1 diabetes (T1D) in children/adolescents with autoimmune thyroid disease (AITD, and family members of AITD patients with islet autoimmunity. Islet-cell cytoplasmic, glutamic-acid decarboxylase, and tyrosine-phosphatase autoantibodies were measured in 161 AITD patients [(127 with autoimmune thyroiditis (AT); 34 with Graves' disease (GD)], 20 family members of AITD patients with islet autoimmunity, and 155 age-matched controls. Islet autoimmunity was found in 10.6% of AITD patients, significantly more frequent than in controls (1.9%; p=0.002). A higher prevalence of islet autoantibodies was found in females with AITD (p=0.011) but not in males (p=0.16) and AT (p=0.013) but not in GD patients (p=0.19), compared to corresponding controls. Two or three islet autoantibodies were found concurrently in six AITD patients with islet autoimmunity. They all developed T1D and had significantly higher islet autoantibodies titers (p=0.01) than AITD patients with single islet autoantibodies but normal glucose metabolism. T1D was found in 3.7% of AITD patients compared to 0.2% of the age-matched, general Croatian population. Islet autoantibodies were found in 5/20 family members of AITD patients with islet autoimmunity, among which two developed T1D. None of the controls was positive to more than one islet autoantibody or developed T1D. Conclusion: Children/adolescents with AITD (particularly females and patients with AT) represent a risk group for islet autoimmunity and T1D, as well as family members of AITD patients with positive islet autoantibodies, but the last observation must be examined in a more significant number of patients.