Factors for thyroid autoimmunity in children and adolescents with type 1 diabetes mellitus

Introduction. Type I diabetes mellitus (T1DM) is associated with an autoimmune reaction to thyroid antigens including thyroid peroxidase (anti-TPO) and thyroglobulin (anti-Tg). Aims. We determined in children with T1DM the relationship of positive anti-thyroid antibodies to potential risk factors, including, age, gender, duration of diabetes, and glutamic acid decarboxylase antibodies (anti-GAD). Materials and methods. We studied 144 children and adolescents with T1DM. Their age was 12.3 +/- 4.6 (mean +/- SD) years, and duration of diabetes was 4.6 +/- 3.8 years. Anti-thyroid antibodies were determined using a luminescence method and anti-GAD using an enzyme-linked immunosorbent assay. Results. The prevalence rates of anti-thyroid antibodies among the children with T1DM in our study were: anti-TPO (17.4%), anti-Tg (11.1%), and of both anti-thyroid antibodies (10.4%). The presence of serum anti-thyroid antibodies was positively associated with age (16.6 years in those with positive tests versus 12.0 years in those with negative tests, P = 0.027), duration of diabetes (7.4 versus 4.3 years, P = 0.031), and serum TSH (Thyroid-stimulating hormone) levels (4.8 versus 2.3 mu IU/mL, P = 0.002). The presence of both anti-thyroid antibodies was associated with female sex (boys: 4/75 (5.3%), girls: 11/69 (15.9%), chi-square = 6.44, P = 0.04). Subclinical autoimmune thyroiditis (SAIT) was present in 55.5% of the patients with thyroid antibody-positivity and was positively associated with age (16.6 versus 12.0 years, P = 0.001) and diabetes duration (7.6 versus 4.2 years, P = 0.001). Multiple logistic regression analysis revealed that the development of anti-thyroid antibodies was predicted by: 1) the presence of anti-GAD (odds ratio (OR) 1.45, 95% confidence interval (0) 1.09-1.92), 2) the presence of a second anti-thyroid antibody (OR 134.4, 95% CI 7.7-2350.3), and 3) older age (OR 22.9, 95% Cl 1.13-463.2). Conclusions. Thyroid autoimmunity was associated with female gender, increasing age, long diabetes duration, the persistence of anti-GAD, and with TSH elevation, indicating subclinical hypothyroidism.