Increased risk of thyroid autoimmunity in rheumatoid arthritis: a systematic review and meta-analysis

Thyroid autoimmunity, which is the most common immune-mediated disease, is frequently together with other organ- as well as nonorgan-specific autoimmune disorders. Meanwhile, rheumatoid arthritis (RA) is a chronic immune-mediated inflammatory disorder that mainly results in cartilage destruction as well as synovial joint inflammation, and both the adaptive and innate immune responses involve in the progression of this disease. Considering that autoimmune elements may be common characteristics of thyroid autoimmunity and RA, it is likely that both disorders may coexist within some patients. A great number of studies have researched whether an association between thyroid autoimmunity and RA exists; however, the results of these studies have been inconsistent. Most of these studies have included relatively small sample sizes, which have rendered them insufficiently powerful to determine whether there is a relationship between RA and thyroid autoimmunity. The main objective of this meta-analysis was to provide reliable estimates of the extent of any association between thyroid autoimmunity and RA by combining the primary data from all related studies. Literature databases, including the Embase, Medline, Web of Science, Chinese Wanfang, and CBM databases, were searched for studies published from January 1980 to May 2014, with a language restriction of English and Chinese. A total of 1,021 RA cases and 1,500 healthy controls were included in this study. From these data, the odds ratios (OR) and the corresponding 95 % confidence intervals (95 % CI) were calculated. The results of the meta-analysis showed that the prevalence of thyroid autoantibody positivity in patients with RA was higher than that in healthy controls (TgAb: OR 3.17, 95 % CI 2.24-4.49; TPOAb: OR 2.33, 95 % CI 1.24-4.39). The results of this meta-analysis suggest that thyroid autoimmunity is more prevalent in patients with RA than in the control population.