Anti-thyroid antibodies and thyroid dysfunction in rheumatoid arthritis: prevalence and clinical value

The aim of this study was to assess thyroid function as well as the prevalence and clinical value of anti-thyroid antibodies in patients with rheumatoid arthritis (RA).

Seventy patients with active RA (ACR criteria), 9 males and 61 females, mean age 47 years (range 15-77) were analyzed. Anti-thyroperoxidase (TPOAb) and anti-thyroglobulin antibodies (TgAb) were tested using radioimmunoassay. Free thyroxine (FT4) and free triiodothyronine (FT3) and thyroid-stimulating hormone (TSH) serum levels were measured using electro-immunochemiluminescence (ECLIA, Elecsys Roche). Clinical variables, including tender and swollen joint count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF), anti-cyclic citrullinated peptide antibody (anti-CCP) and antinuclear antibodies (ANA) were also evaluated. Statistics were performed by the SPSS statistical software for Windows.

Twenty-six patients (37%) with RA were positive for TPOAb and 16 (23%) for TgAb. In 5 (7.1%) patients TSH level was slightly elevated, ranging between 4.52 and 15.65 UI/ml. The increase of TSH levels was associated with normal FT4 in 3 cases (4.2%) and with reduced FT4 in 2 cases (2.8%). One patient (1.5%) had low TSH serum value along with normal FT4. No differences in clinical and serological data between anti-thyroid positive and negative patients were observed.

Our study shows an increased prevalence of anti-thyroid antibodies in RA patients with a low prevalence of hormonal alterations. However, anti-thyroid antibodies do not seem to identify any peculiar RA phenotype.