Thyroid and adrenal autoimmunity in children with newly diagnosed type 1 diabetes mellitus

Objectives: Individuals with type 1 diabetes mellitus (T1DM) are at risk of further autoimmune diseases. This study aimed to identify the prevalence of thyroid and adrenal autoimmunity and dysfunction in children with T1DM. Material and Methods: A retrospective case review was conducted of children presenting to the Royal Hospital for Children, Glasgow, with newly diagnosed T1DM between 1 September 2017 and 1 September 2022. Data on thyroid peroxidase (TPO) and adrenal antibody status and function were retrieved from diagnosis until 24 May 2024. Results: 504 children were diagnosed with T1DM, with data available for 384 (53% female). Median age at T1DM diagnosis was 9.6 years (range 0.9–16.1 year). Median duration of follow-up was 4.1 years (range 1.7–6.7 years). TPO antibodies were tested at T1DM diagnosis in 364 (95%); 65 (18%) had raised TPO antibodies, with girls more likely to test positive (73%, P = <0.001). Four children not tested for TPO antibodies at diagnosis tested positive during subsequent screening. Overall, 10/69 (14%) developed hypothyroidism, with 8 diagnosed at initial TPO antibody detection. Two developed hypothyroidism 2.3 and 2.4 years later. Adrenal antibody status was obtained at T1DM diagnosis in 380 (99%). Three children tested positive (two children at diagnosis and one before diagnosis). No child with positive antibodies developed adrenal dysfunction after a median of 4-year follow-up (range 2.0–5.9 years). Conclusion: Hypothyroidism occurred in 14% of T1DM children with raised TPO antibodies; most had detectable TPO antibodies at T1DM diagnosis. Adrenal autoantibodies and subsequent adrenal dysfunction were infrequent.