Relationship between rheumatoid arthritis activity and antithyroid antibodies

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.