Evaluation of a radioreceptor assay for TSH receptor autoantibodies

Abstract

A commercial radioreceptor assay for TSH receptor autoantibodies (TRAb), based on solubilized porcine receptor and purified radio-iodinated bovine TSH, was tested in 264 subjects with a variety of thyroid disorders. The sensitivity of the assay for the detection of hyperthyroid Graves' disease was 91%. The assay specificity for Graves' disease was 95%. With the exception of one patient with Hashimoto's disease and one patient with de Quervain's subacute thyroiditis no subjects other than Graves' patients had detectable TRAb. Thus purely blocking TSH receptor autoantibodies were not detected with the assay. One female with thyroxine-treated idiopathic primary hypothyroidism who had given birth to two children with transiently elevated TSH, was found to have a circulating TSH-binding substance that resulted in an abnormally negative TRAb value, and highly discrepant results when TSH was measured with a double antibody TSH radioimmunoassay and an immunoradiometric assay. The TSH-binding substance was precipitated like a protein, but was not IgG. Similar findings have not previously been reported.

Peak Systolic Velocity of Superior Thyroid Artery for the Differential Diagnosis of Thyrotoxicosis

“…Sometimes it can be quite challenging, due to the possibility of painless thyroiditis and early-stage atypical GD [9]. Generally, the following methods are commonly used in the differentiation of transient thyrotoxicosis and GD: thyroid technetium 99 scan, RAIU assay, T3/T4 ratio [10], [11], serum markers such as total activity of alkaline phosphatase [12] and TRAb [4], [13], [14]. Serological assays such as FT3/FT4 ratio [10], [11] and alkaline phosphatase activity had limited values in the differential diagnosis [10], [12].…”

Mean Peak Systolic Velocity of the Superior Thyroid Artery is Correlated with Radioactive Iodine Uptake in Untreated Thyrotoxicosis

“…Improvements in diagnostic technology have allowed early diagnosis of Graves' disease, even without its typical manifestations such as exophthalmos, pretibial myxoedema or goitre. 4 Several tests, including radioactive iodine uptake (RAIU), technetium thyroid scan, ratio of serum tri-iodothyronine to thyroxine, 5 serum total alkaline phosphatase activity 6 and serum antithyrotropin receptor antibody (TRAb) 7 have been used for the differential diagnosis of transient thyrotoxicosis and Graves' disease. These tests are not generally available in hospitals and clinics in China, and it can take several days to obtain the results.…”