New assay systems for thyrotropin receptor antibodies

The detection of autoantibodies to the TSH receptor is a useful tool for the diagnosis of Graves’ disease. Historically, there are two established methods for this purpose. One is the radioreceptor assay based on the porcine TSH-R, where autoantibodies and labelled bovine TSH compete for the binding sites of the receptor. The other method is based on the ability of some autoantibodies similar to TSH to induce the second messenger cAMP in certain cell lines. These so-called bioassays are able to distinguish between stimulating or blocking autoantibodies, based on their biologic activity, to either enhance or inhibit the cAMP production. Ten years after the cloning of the human TSH-R, these two basic detection principles were finally improved. In this article, the author summarizes the latest developments in TSH-R autoantibody assay technology and outlines the current research on alternative approaches, such as direct-binding assays. Controversies related to autoantibody terminology and assay interpretation are also addressed.