Swelling and bulging of the eyes caused by excessive production of thyroid hormones; also known as Graves ophthalmopathy. The thyroid gland, located to the front and sides of the windpipe (trachea) just above the breastbone (sternum), produces thyroid hormones that control important body processes, such as the rate of metabolism, body temperature and muscle tone and vigor. In Graves disease, the thyroid gland becomes overly active (hyperthyroidism) and produces excessive levels of hormones. Treatment consists of medication to block the effects of thyroid hormones, destruction of a portion of the thyroid with radiation, or surgical removal of part of the thyroid.