When the autoimmune system goes awry and attacks the thyroid, most people develop Hashimoto's disease as a result. A smaller percentage of these people develop Graves' disease, which is the most common cause of hyperthyroidism in the United States. In this chapter, you'll take a closer look at what Graves' disease is, including its causes, symptoms, diagnosis, and treatment options. You'll also learn what other autoimmune diseases to be on the lookout for as a person with Graves'.