Thyroid Disorders in Korean Patients with Rheumatoid Arthritis / 대한류마티스학회지

ABSTRACT

OBJECTIVE: To define the prevalence of thyroid dysfunction and autoantibodies in rheumatoid arthritis(RA). A prospective controlled study was conducted on 62 RA patients and 55 controls with non-inflammatory rheumatic diseases (3 osteoarthritis, 6 fibromyalgia, 4 carpal tunnel syndrome and 42 patients with nonspecific joint pain). All subjects were tested for T3, T4, TSH, FT4, RAIU, rheumatoid factor and ANA. Anti-thyroglobulin (TG) Ab and anti-microsomal (Mic) Ab were assayed using a more sensitive direct assay of RIA and TSH-R Ab (TRAb) using competitive radioimmunoassay. Thyroid dysfunction was observed in 10 RA patients (16.2%) of which 6 patients had hypothyroidism and 4 patients hyperthyroidism, and was significantly more prevalent in RA (p=0.026). Anti-Mic Ab was significantly more prevalent in RA patients. The frequencies of anti-Mic Ab and anti-TG Ab in RA patients were 69.4% and 58.1% (cut-off value was 0.3U/ml), but were 16.1% and 12.9% when those over 10U/ml were calculated. Thyroid dysfunction was not present when either of anti-TG Ab or anti-Mic Ab was below 0.3U/ml. The prevalence of thyroid dysfunction or autoantibodies were not different according to the presence of RF or ANA. CONCLUSION: The prevalence of thyroid dysfunction and autoantibodies were significantly increased in RA patients and the variance of the latter in other reports might be explained at least partially by difference in cut-off values of different methods. Thyroid dysfunction may not develop when either of anti-Mic Ab or anti-TG Ab is below 0.3 U/ml in RA.