Monoclonal Antibodies and the Thyrotropin Receptor

Thyrotropin (TSH) is a pituitary glycoprotein hormone whose primary role is to regulate thyroid cell function (Dumont, 1971; Field, 1980; Robbins et al., 1980; Kohn et al., 1983). The interaction of TSH with a specific receptor on the thyroid cell surface induces changes in adenylate cylcase activity which result in the following tissue responses: enhanced iodide uptake, thyroglobulin biosynthesis, iodination of thyroglobulin, degradation of iodinated thyroglobulin to form thyroid hormone, and the release of thyroid hormone (T3 and T4) into the bloodstream. Although changes in all of the above activities have been and can be used to define receptor function, definition of the structure of the TSH receptor on a molecular level, as with all other receptors, has required the identification of specific membrane components using binding studies and 125I-labeled hormone (Kohn, 1978; Kohn and Shifrin, 1982; Kohn et al., 1983).