TSH RECEPTOR BINDING AND THYROID STIMULATION BY SERA FROM PATIENTS WITH GRAVES' DISEASE

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Abstract
An investigation of the ability of TSH receptor antibodies to bind to the TSH receptor and stimulate thyroid function is described. Binding studies were carried out using 125I-labeled TSH and detergent solubilized porcine TSH receptors, and the parameter of thyroid stimulation employed was 125I-organification in isolated porcine thyroid cells. Different Graves'' sera showed different dose-response relationships and 3 types of antibody activity were evident in the 6 samples studied. In 2 samples receptor binding and thyroid stimulating activities were approximately parallel. In 2 receptor binding was detectable at lower doses than stimulation while in the last 2 stimulation was detectable at lower doses than binding. These characteristics are probably due to different populations of receptor antibodies which exhibit different degrees of TSH agonism. One of the reasons for the relatively poor correlation between TSH receptor binding and thyroid stimulation observed in series of individual Graves'' sera may be the presence of different populations of antibodies showing different dose-response relationships with regard to binding and stimulation.