The prevalence of thyroid dysfunction and thyroid autoantibodies among patients with rheumatoid arthritis

Background and objective: Rheumatoid arthritis is a chronic and inflammatory autoimmune systemic disease of unknown cause that may affect many tissues and organs. Rheumatoid arthritis and thyroid disorders may occur in the patient simultaneously. The main antigens that give rise to thyroid antibodies are thyroglobulin, thyroid peroxidase, anti-cyclic citrullinated protein, and thyroid hormone receptor. This study aimed to determine the frequency of thyroid dysfunction and seroprevalence of anti-thyroid antibody in patients with rheumatoid arthritis and its association with inflammatory marker C-reactive protein. Methods: A cross-sectional study was performed at Rizgari Teaching Hospital and CMC private hospital, Erbil, Iraq. From 15 January to15 October 2020. A hundred patients with rheumatoid arthritis were included in the study, in addition to 70 controls. The serum levels of biomarkers were determined by the chemiluminescent immunoassay method. Results: Patients with rheumatoid arthritis had 6% of thyroid dysfunctions. Regarding the prevalence of thyroid autoantibodies in patients with rheumatoid arthritis, 9% had positive anti-thyroid peroxidase, 13% had positive anti-thyroglobulin, and 6% were positive for a combination of both. There was a statistically significant (P <0.001) high level of serum anti-cyclic citrullinated protein and C-reactive protein in rheumatoid arthritis than in control. Euthyroid profiles were 73% inrheumatoid arthritis patients and 82.9% in control. Conclusion: The study delineated the co-existence of thyroid disorder in rheumatoid arthritis patients with or without autoimmune origin, besides the increased prevalence of auto-thyroid antibody among rheumatoid arthritis with thyroid dysfunction.