Thyroid disorders in patients with myasthenia gravis: A systematic review and meta-analysis

Our purpose was to determine the prevalence of thyroid disorders in myasthenia gravis (MG) or whether MG was associated with an increased risk of thyroid disorders. Pubmed, Embase, Web of Science, Cochrane database, Google Scholar and the Chinese Biomedical Databases were searched about the relationship between thyroid disorders and myasthenia gravis up to November 30, 2018, without language restrictions. The prevalence and relative risk (RR) for thyroid disorders were pooled by the R and STATA software. 39 papers with 24,927 MG patients were ultimately included for analysis in this meta-analysis. The pooled estimate of thyroid autoimmunity prevalence in MG patients was 10.1% (95%CI 6.7%–15.1%). Subgroups in patients with thyroid autoimmunity showed the prevalence of positive TGAb was the highest in MG patients (12.6%, 95%CI 8.1%–19.1%), followed by GD (6.0%, 95%CI 4.2%–8.5%), HT (4.6%, 95%CI 1.9%–10.5%). Moreover, the pooled estimated prevalence of thyroid dysfunction in MG patients was 6.8% (95%CI 4.6%–9.8%). After stratification, the results showed the prevalence of hyperthyroidism and hypothyroidism in MG cases were 5.6% (95%CI 3.9%–8.0%) and 2.6% (95%CI 1.7%–4.1%), respectively. In addition, meta-analysis of 2 studies showed that MG was significantly associated with the increased risk of thyroid autoimmunity (OR = 2.86; 95%CI 1.54–5.28, P = .001). This systemic review and meta-analysis provides reliable evidence that thyroid disorders are prevalent in MG, especially TGAb positivity, GD, hyperthyroidism, and HT, and MG is associated with increased risk for thyroid autoimmunity.