*3.2.1. Radioreceptor assay*

Radioreceptor assay is most readily available and most widely used in clinical practice. Basic principle of radioreceptor assay is displacement of labeled TSH from solubilized TSHR from patient's serum. This TSH- binding inhibitory immunoglobulins (TBII) assay does not provide information regarding the functionality of TSHR-Ab. TBII assays are cheaper and having good precision. The first generation TBII assays have sensitivity of 75-95% in untreated Graves' disease patients. Most recently a monoclonal human antibody to TSHR is used. This second generation radio-receptor assay has sensitivity of 99% and very high specificity. 21
