The TSH receptor is present on the basal surface of thyroid follicular cells. It is involved in regulating thyrocyte cell growth and function by mediating thyroid stimulating hormone (TSH) action. The TSH receptor is also the target autoantigen in autoimmune thyroid diseases. Autoantibodies to the TSH receptor that stimulate cAMP production in thyrocyte cells, called thyroid stimulating antibodies, are responsible for the hyperthyroidism of Graves Disease. This disease is the most common cause of hyperthyroidism, hence causing the thyroid gland to produce too much thyroid hormones. This test is useful when a patient has symptoms of hyperthyroidism; to monitor effectiveness of anti-thyroid therapy, and to help predict remission.