Significance of Thyroid Stimulating Antibody and Long Term Follow Upin Patients with Euthyroid Graves' Disease

Abstract

We examined 13 patients with euthyroid Graves' disease suspected ophthalmologically, by comparing them with 20 patients with untreated Graves' disease and by following them up for 5 to 10 years. They had Graves' ophthalmopathy (NOSPECS class II-IV) without other ocular diseases, normal levels of serum thyroid hormones, and no previous history of Graves' disease. Proptosisin euthyroid Graves' disease was not significantly different from thatin untreated Graves' disease.in 3 patients with euthyroid Graves' disease, TSH was suppressed. There was either no TSH response to TRH or it was lowin 7 of 12 patients examined. the result of a T3-suppression test was abnormalin 8 of 11 patients examined. Titers of serum TGHA, MCHA, TSH-binding inhibitory immunoglobulin (TBII), and thyroid stimulating antibody (TSAb) were significantly lowerin patients with euthyroid Graves' disease compared thanin patients with untreated Graves' disease. TSAb, however, was positivein 12 of 13 (92%) patients.in spite of positive TSAb, 9 of 13 patients with euthyroid Graves' disease had normal radioactive iodine uptake (RAID). During the observation period, various abnormalitiesin thyroid function developed: persistent hyperthyroidismin 5 patients (38%), transient thyrotoxicosisin 2 (15%) and transient hypothyroidismin 1 (8%). We conclude that euthyroid Graves' disease is a subtype of Graves' disease that minimally develops thyrotoxicosisin spite of the existence of TSAb due to some mechanism inhibiting thyroid growth or stimulation, and that the measurement of TSAb provides a useful marker for the diagnosis of this disease. © 1995, The Japan Endocrine Society. All rights reserved.