Clinical Utility of TSH Receptor Antibodies

CONTEXT: TSH receptor antibodies (TRAb) cause Graves' disease (GD) hyperthyroidism. Widely available TRAb measurement methods have been significantly improved recently. However, the role of TRAb measurement in the differential diagnosis of hyperthyroidism, the prediction of remission of GD hyperthyroidism, the prediction of fetal/neonatal thyrotoxicosis, and the clinical assessment of Graves' ophthalmopathy (GO) are controversial. EVIDENCE ACQUISITION: We reviewed and analyzed the literature reporting primary data on the clinical use of TRAb. We focused our analyses on clinical studies analyzing third-generation TRAb assays. EVIDENCE SYNTHESIS: The performance of TRAb in the differential diagnosis of overt hyperthyroidism is excellent, with sensitivity and specificity in the upper 90%. TRAb can accurately predict short-term relapses of hyperthyroidism after a course of antithyroid drugs but are less effective in predicting long-term relapses or remissions. Pregnancies in women with GD with negative TRAb are highly unlikely to result in fetal hyperthyroidism, whereas high titers of TRAb in pregnancy require careful fetal monitoring. GD patients with GO frequently have high TRAb levels. However, there are insufficient data to use the test to predict the clinical course of GO and response to treatment. CONCLUSIONS: Third-generation TRAb assays are suitable in the differential diagnosis of hyperthyroidism. In GD, TRAb should be tested before deciding whether methimazole can be stopped. TRAb should be used in pregnant women with GD to assess the risk of fetal thyrotoxicosis. The use of TRAb in GO requires further studies.