In this study, we investigated Thyrotropin Receptor Antibody (TRab) levels in Hashimoto and Graves' diseases. A total of 189 patients and 25 controls were assessed, retrospectively. Fifty-four of the 189 patients had euthyroid Hashimoto thyroiditis and the remaining group had Graves' disease. In order to assess the TRab level differences in the subgroups, patients with Graves disease were subdivided into 4 groups according to their clinical status and the presence of ophthalmopathy as follows: hyperthyroid Graves' disease without ophthalmopathy (Group A, n=16); hyperthyroid Graves' disease with ophthalmopathy (Group B, n=43); euthyroid Graves' disease without ophthalmopathy (Group C, n=28); and euthyroid Graves' disease with ophthalmopathy (Group D, n=48). The incidence of positive TRab assay in the Hashimoto group was 7.4% (ranged 0.15-21.00), whereas 62% were positive in the Graves' group (range 0.007-187.1). By means of TRab titers there was no statistical difference found between the Hashimoto group and the control group. In group A, TRab was detected in 12 patients (75%) and in group C, in 22 patients (51%). In groups B and D, TRab was detected in 22 patients (80%) and 28 patients (59%) respectively. It can be concluded that as a practical method, TRab assay may be useful in making a differential diagnosis of Graves' disease rather than other Autoimmune Thyroid Diseases (AlTD's), for patients who show no signs of ophthalmopathy and/or hyperthyroidism.
Keywords: TSH receptor antibody (TRAb), Autoimmune Thyroid Disease (AITD), Graves' disease