Thyroid autoimmunity in Type 1 diabetes: systematic review and meta-analysis

AimsTo review the incidence and evidence for screening for thyroid autoimmunity and thyroid dysfunction in Type1 diabetes. MethodsSystematic review and meta-analysis. Inclusion criteria were prospective cohort studies screening for thyroid autoimmunity and/or dysfunction (defined as an abnormal thyroid-stimulating hormone level) in Type1 diabetes. Exclusion criteria included pregnancy and thyroid dysfunction before diabetes onset. Outcomes examined were: incidence of thyroid autoimmunity and/or dysfunction; association between thyroid autoimmunity and dysfunction; and cost-effectiveness. Data sources were MEDLINE, EMBASE, the Cochrane Library, manual searching and contact with authors, with limitations to English language and human studies. Meta-analysis was performed using random effects models. ResultsWe identified 14 eligible studies, involving 2972 young people and 789 adults with Type1 diabetes. Follow-up ranged from 1-18years. None of the studies were of good methodological quality (Newcastle Ottowa Scale score >7). The incidence of thyroid dysfunction (11 studies) ranged from 27 (95%CI 15-45) to 246 (95%CI 118-453) per 10000 patient-years and thyroid autoimmunity (four studies) from 13 (95%CI 0.3-71) to 326 (95%CI 194-510). The risk of thyroid dysfunction was higher in those with thyroid autoimmunity: summary risk ratio 25 (95%CI 9-71) and was higher in children (49, 95%CI 16-150) compared with adults (7, 95%CI 3-13). No studies examined cost-effectiveness of screening. ConclusionsThere is a markedly increased risk of thyroid dysfunction in people with Type1 diabetes and thyroid autoimmunity. The optimal method or frequency of screening could not be determined from available data. Future studies should examine whether screening improves clinical outcomes in this population.