Graves’ disease is an autoimmune condition of the thyroid gland, a hormone-producing gland located in the throat just inferior to (to the “South” of) the “Adam’s apple.” In an autoimmune disease, the body’s natural defenses against infection — called the immune system — turns against the body and starts attacking its own tissues. This involves the creation of autoantibodies, defense molecules that are directed against specific body tissues instead of against invading bacteria or viruses. In Graves’ disease, the autoantibodies that are produced attack the thyroid gland. However, instead of destroying the thyroid these autoantibodies activate receptors on the surface of the gland and stimulate it to release more thyroid hormones than normal. When the thyroid gland releases higher-than-normal levels of thyroid hormones, it is called hyperthyroidism.

The symptoms of Graves’ disease are caused by excessive levels of the thyroid hormones known as thyroxine and triiodothyronine. These iodine-containing hormones increase the rate of metabolism in the body and affect the growth and function of many body systems.  

As with most autoimmune diseases, scientists do not know what causes the immune system to attack the thyroid gland in Graves’ disease. A combination of factors is likely involved including heredity, hormones, age, and stress.