Graves Disease is an autoimmune disease. This causes your own immune system to think that the thyroid is a foreigner and it attacks the thyroid gland to produce too much thyroid hormone. This causes to the pituitary gland to stop producing thyroid stimulating hormone (TSH) and the thyroid to overproduce thyroid horomones, which are triiodothyronine (T3) and thyroxine (T4).