The most common underlying cause of hyperthyroidism is Graves' Disease , a condition named for an Irish doctor who first described the condition. Graves' disease affects women much more often than men. This condition is sometimes called diffuse toxic goiter, because the entire thyroid gland is enlarged. Although it can occur at any age, it most commonly affects younger people. Graves' disease is an autoimmune disease , a condition caused by the patient's own immune system turning against the patient's own thyroid gland.
Hyperthyroidism is caused by antibodies directed against the thyroid gland.
Graves' disease tends to run in families, but no one yet understands precisely what triggers the onset of the condition. Most patients with Graves' disease have mild or no obvious eye involvement. Their eyes may feel irritated or they may look like they are staring. However, one out of 20 people with Graves' disease suffer more severe eye problems, which can include bulging of the eyes, severe inflammation, double vision, or blurred vision. If these serious problems are not recognized and treated, they can permanently damage the eyes and even cause blindness.