Thyroid autoimmunity in children with features of both type 1 and type 2 diabetes

Aim/hypothesis: To assess the prevalence of autoimmune thyroid disease (ATD) in insulin-treated youth with clinical features of type 2 diabetes mellitus (T2DM). Methods: We evaluated prevalence of thyroid peroxidase (TPO) and thyroglobulin (TGA) antibodies at onset of insulin-treated diabetes and follow-up in 183 White and Black children. Of these, 136 had a body mass index (BMI) < 85th percentile with 122 (89%) positive for beta-cell autoimmunity [type 1 diabetes mellitus (T1DM)/group I], 25 were overweight (BMI >= 85thpercentile) with or without acanthosis nigricans with beta-cell autoimmunity ['double' diabetes (DD)/group II], and 22 were overweight with no conventional beta-cell autoantibodies (group III). Results: The prevalence of TPO and/or TGA was 39 and 29% (p = 0.19) in White and Black children and 39, 32, and 0% (p = 0.007) in groups I, II, and III, respectively. After a median follow-up of 60 months, 3.7, 4.3, and 0% developed hypothyroidism (increased thyroid-stimulating hormone with or without decreased free T4) in groups I, II, and III, respectively (p = 0.6). In subjects with TPO and/or TGA, hypothyroidism developed in 10 and 14% of groups I and II, respectively (p = 0.7). No child without thyroid antibodies developed hypothyroidism. Conclusions: In patients with clinical features of T2DM who have evidence of beta-cell autoimmunity (DD), the frequency of thyroid antibodies and ATD is similar to that in classical T1DM. This suggests that TIDM comorbidities may be common in clinical T2DM patients who have beta-cell autoimmunity. Despite their obesity, youth with insulin-requiring diabetes should be screened for thyroid and possibly other T1DM-associated autoimmune diseases.