Introduction: Rheumatoid arthritis (RA) is known to be associated with a higher prevalence of antithyroid antibodies and autoimmune thyroid disease, but there have been few studies regarding the correlations between the presence of these antibodies and RA activity.
Objectives: The aim of this study was to analyze the relationship between antithyroid antibody titers and selected parameters of RA activity.
Patients and methods: A total of 75 consecutive hospitalized patients with RA were enrolled into the study. Levels of antithyroid peroxidase antibodies (aTPO), antithyroglobulin antibodies (aTG), and antithyrotropin receptor antibodies (aTSH-R) were measured. The analysis of disease activity was based on the disease activity score with 28-joint count (DAS28), duration of morning stiffness, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) and hemoglobin levels.
Results: Antithyroid antibodies were present in 13.3% of the patients (n = 10), aTPO in 9.3% (n = 7), aTG in 8% (n = 6), and aTPO and aTG in 4% (n = 3); aTSH-R was not detected in any of the patients. Significant positive correlations (P <0.05) were observed between aTPO and DAS28 (r = 0.35, P = 0.002), aTG and ESR (r = 0.25, P = 0.02), and aTG and CRP (r = 0.23, P = 0.04). There were significant differences in the mean DAS28 between the aTPO‑positive and aTPO‑negative groups (5.35; 95% confidence interval [CI], 4.39-6.3 vs. 4.12, respectively; 95% Cl, 3.81-4.43; P = 0.017) and between the aTG-positive and aTG-negative groups (5.65; 95% Cl: 4.64-6.67 vs. 4.11; 95% Cl: 3.81-4.41; P = 0.005; respectively).
Conclusions: Our results suggest that RA activity may be associated with the presence of antithyroid antibodies. This finding could be useful in the clinical evaluation of RA patients.