Graves' disease is an autoimmune disorder that affects the thyroid gland, which produces hormones that control many of the body's functions. Graves' disease causes the thyroid gland to produce too much thyroid hormone (hyperthyroidism), which may make a person's heart pound and beat irregularly and may cause nervousness, mood changes, weakness, and fatigue.

Signs and symptoms of Graves' disease include diarrhea, rapid heart rate, inability to tolerate heat, and weight loss.

Graves' disease is the most common cause of hyperthyroidism. It tends to run in families. And it affects women more often than men. It can develop at any age. But most commonly it affects people between ages 30 and 50.