[Thyroid-stimulating hormone receptor antibodies in the differential diagnosis of toxic goiter]

The production of stimulating thyroid-stimulating hormone (TSH) receptor antibodies (TSHR-Ab) whose level measurement has come into clinical use underlies the pathogenesis of Graves'disease (GD). This paper deals with the diagnostic and differentially diagnostic value of measurement of TSHR-Ab levels using two first-generation techniques (with heterological TSH): radioreceptor assay ("CIS bio international", France) and enzyme immunoassay ("Medizym" T.R.A."). The levels of TSHT-Ab, as well as thyroid peroxidase antibodies (TH-Ab) and thyroglobulin antibodies (TG-Ab) were studied in 206 patients among whom 176 patients were diagnosed as having GD and 30 had clinical thyroid functional autonomy (FA) generally appeared as multinodal toxic goiter. A comparative analysis of these two assays did not reveal some advantages of them and their results showed a significantly positive correlation (r = 0.91; p < 0.001). The diagnostic sensitivity of the assays was about 80-88% and their specificity was 60-70%. The findings led to the conclusion that in the absence of significant endocrine ophthalmopathy (EOF), clinical and routine instrumental and laboratory studies fail to differentiate GD and throid FA to sufficient accuracy whereas the measurement of the levels of TSHR-Ab substantially makes diagnosis easier. Moreover, it has been shown that the determination of the level of TBII using the test systems containing heterological TSH may not be used for the evaluation of the course of EOF.