Hypothalamus-hypophysis-thyroid axis, triidothyronine and antithyroid antibodies in patients with primary and secondary Sjogren's syndrome

It has been well established that, antithyroglobulin antibodies (ATG) and a nti-microsomal antibodies (AMC) may be present in various thyroid disorders and other systemic autoimmune diseases, including Sjogren's syndrome (SS). However, presence of circulating autoantibodies to thyroid hormones, i.e. both to triiodothyronine (T3) and tetraiodothyronine (T4), has not been stu died extensively in SS. Autoantibodies to T3 and T4 are very important, bec ause serum T3 and T4 levels may be detected spuriously higher or lower, due to the presence of these autoantibodies. Their presence should be suspecte d when measured serum thyroid hormone levels are not consistent with clinic al status of the patient. SS is a slowly progressive, inflammatory autoimmu ne disease, affecting primarily the exocrine glands. Thyroid gland, being a target in some autoimmune diseases, is well known to be affected in SS as well. Keeping this possibility in mind, we investigated T3 autoantibody lev els and thyroid gland involvement in patients with SS. Twenty-six SS patients (F/M:22/4) with a mean age of 46,6 years, were recru ited in this study. Twelve of them we-re accepted as primary SS (pSS), whil e others had secondary SS (sSS) (7 with rheumatoid arthritis (RA), 3 with s ystemic lupus erythematosus (SLE), 3 with progressive systemic sclerosis (P SS) and 1 with sarcoidosis). Thyroid function tests, including T3, T4, fT3, fT4, TSH, ATG, AMC, T3 antibody measurements, thyroid scintigraphy, thyroi d ultrasonography and TRH stimulation tests were performed in all patients. We compared our results with those of the twenty healthy normal controls. Serum ATG and/or AMC were detected in three patients with pSS (25%) and no patients with sSS. No significant difference could be shown in the other pa rameters, including T3 autoantibodies and thyroid function tests. TRH stimu lation test was also normal, showing that the hypothalamus-hypophysis-thyro id axis was not affected in patients both with pSS and sSS. In conclusion, we found that T3 autoantibody levels in pSS, were not signif icantly higher than sSS and normal controls.