Thyroid disease associated with rheumatoid arthritis is not adequately screened with a sensitive chemiluminescence thyrotrophin assay

The objective of this study was to screen for thyroidopathies in patients w ith rheumatoid arthritis (RA). Screening for thyroid disorders is advocated in patients with autoimmune diseases, and rheumatoid arthritis has been li nked to thyroid autoimmune disorders, more particularly Hashimoto's thyroid itis and sometimes Graves' disease. We performed thyroid disease screening in 69 patients with RA free of medication for at least a 2 weeks period, no t in remission,and in 65 patients with osteoarthritis (OA). The latter were studied as a control group of non-autoimmune arthritis patients. Basal lev els of thyrotrophin (TSH) were measured using a sensitive chemiluminescence serum TSH assay. Serum antithyroperoxidase and antithyroglobulin (anti-T-3 ) autoantibodies were measured as well. ii TSH values were found to be outs ide the normal limits, serum total thyroxine, total triiodothyronine (T-3), resin T-3 uptake, the free thyroxine index (FT4I) and free triiodothyronin e index(FT3I) were evaluated. Rheumatoid arthritis patients exhibited stati stically significant lower mean TSH values as compared to OA patients. Howe ver, RA patients with low TSH values did not have elevated FT4I. Previous u se of corticosteroids in some of the RA patients may be responsible for the se results. The autoantibodies levels did not differ between the two groups . We conclude that thyroid function screening with sensitive TSH assays is not sufficient for assessment of early stages of autoimmune thyroidopathies in patients with RA. Thyroid hormones should also be estimated.