The Association Between Thyroid Dysfunction, Autoimmune Thyroid Disease, and Rheumatoid Arthritis Disease Severity

Introduction Rheumatoid Arthritis (RA) and autoimmune thyroid disease (AITD) are the two most prevalent autoimmune diseases that can coexist due to their similar pathogenesis. Considering the potential effect of AITD on the severity of RA disease, this study aimed to determine the association between thyroid dysfunction, anti-thyroid peroxidase (anti-TPO) positivity, AITD, and RA disease severity in the Iranian population. Materials and methods Three hundred and fifty RA patients who presented to Shahid Beheshti tertiary care center, Qom, Iran, were included in this cross-sectional study. The data were collected through the patients’ medical records, interviews, physical examinations, and laboratory investigations. The disease activity score in 28 joints for RA with ESR (DAS-28-ESR) was used to divide patients into three groups, remission (DAS-28-ESR ⍰2.6), mild-to-moderate (2.6 5.1). Results Using the method explained beforehand, 111, 96, 138 patients were sorted into remission, mild-to-moderate, and severe disease activity groups, respectively. Anti-TPO antibody positivity was 2.93 times more prevalent among patients with higher severity of disease than in remission (OR: 2.93; P-value < 0.001). Patients suffering from a more severe form of the disease were almost 2.7 times more probable to have AITD (OR = 2.71; P-value < 0.001) and 82% more likely to have thyroid dysfunction than the patients in remission (OR = 1.82; P-value = 0.006). Conclusions It was demonstrated that thyroid dysfunction, anti-TPO antibody positivity, and AITD were significantly more common among RA patients with higher disease activity.