Gravesâ disease is an autoimmune disorder. It causes your thyroid gland to create too much thyroid hormone in the body. This condition is known as hyperthyroidism. Gravesâ disease is one of the most common forms of hyperthyroidism. In Gravesâ disease, your immune system creates antibodies known as thyroid-stimulating immunoglobulins. These antibodies then attach to healthy thyroid cells. They can cause your thyroid to create too much thyroid hormone.