Graves' disease is a common form of hyperthyroidism or overactive thyroid. It is a condition where the body???s immune system attacks the thyroid gland causing it to enlarge and produce high levels of thyroid hormones. Excessive amounts of hormone cause symptoms such as fatigue, weight loss, muscle weakness, sleeplessness, and rapid heartbeat. Inflammation and swelling in the soft tissues and muscles around the eyes can cause the eyeballs to bulge from the sockets, a distinguishing symptom of Graves??? disease.