TSH receptor antibody (TRAb) plays a key role in the pathogenesis of
Graves' disease (GD), and its levels correlate with the
clinical course. The second- and third-generation TRAb assays have >95% sensitivity and specificity for the diagnosis of GD and have improved the utility of TRAb to predict relapse. TRAb levels decline with
antithyroid drug (ATD)
therapy and after
thyroidectomy. Its level increases for a year following radioactive
iodine (RAI)
therapy, with a gradual fall thereafter. TRAb level >12 IU/l at diagnosis of GD is associated with 60% risk of relapse at 2 years and 84% at 4 years. The prediction of risk of relapse improves further to >90% with TRAb >7·5 IU/l at 12 months or >3·85 IU/l at cessation of ATD
therapy. TRAb tests are not expensive, and hence, TRAb measurements at presentation, after 12 months and/or 18 months (at cessation) of ATD
therapy, could potentially guide treatment choices in GD. Elevated TRAb favours definitive treatment in the form of RAI or
thyroidectomy, depending on the presence or absence of moderate-to-severe
Graves' ophthalmopathy (GO) and the ability to comply with radiation protection requirements. Use of ATDs in early pregnancy is associated with increased risk of congenital anomalies; early ablative treatment (RAI/surgery) should be considered in women of childbearing age at higher risk of relapse of GD. TRAb ≥5 IU/l in pregnant women with current or previously treated GD is associated with increased risk of foetal and neonatal
thyrotoxicosis, and hence needs close monitoring. TRAb levels parallel the course of GO, and elevated TRAb is an indication for
steroid prophylaxis to prevent progression of GO with RAI
therapy.