Graves' disease is an autoimmune disorder that leads to overactivity of the thyroid gland (hyperthyroidism).It is caused by an abnormal immune system response that causes the thyroid gland to produce too much thyroid hormones. Graves disease is the most common cause of hyperthyroidism andoccurs mostoften in women over age 20. However, the disorder may occur at any age and may affect males as well.Treatmentmayinclude radioiodine therapy, antithyroid drugs, and/or thyroid surgery.