Thyroid abnormal function and and/or autoimmune thyroid disease (ATD) are observed in 6% to 33.8% patients with rheumatoid arthritis (RA).
The aim of the study was to determine whether ATD is more prevalent in patients with RA compared to the control group involving age and sex-matched subjects without RA and whether these patients should be screened for thyroid disease.
In 100 patients with RA and 55 patients without RA (control group) hormonal thyroid function and antithyroid antibodies were assessed.
ATD was more prevalent (16%) in patients with RA than in the control group (9%). The difference was no statistically significant. The RA patients with concomitant ATD had lower RA activity than non-ATD RA patients. Antithyreoglobulin (anti-TG) and antithyroid peroxidase (anti-TPO) antibodies were present in similar percentage of patients with RA (12% and 15%, respectively) and in the control group (9% and 18%, respectively). The most common thyroid dysfunction observed in both groups was subclinical hypothyroidism. An association between thyroid dysfunction and clinical symptoms suggestive of thyroid disease in RA patients was not demonstrated. In patients with RA low free triiodothyronine concentrations were significantly more common.
A higher prevalence of ATD in female RA patients compared with controls indicates the need for screening not only of thyroid function, but also of the presence of anti-TPO antibodies as the ATD marker in RA patients. Their presence does not correlate with the occurrence of thyroid disorders in RA patients. Monitoring of thyroid function is of particular importance since as already shown the course of thyroid disease in RA patients is often asymptomatic.