Graves' disease, or hyperthyroidism (hahy-per-thahy-roi-diz-uh m), is a condition that causes your thyroid gland to make too much thyroid hormone.
The thyroid gland is located in the neck and is shaped like a butterfly. The thyroid gland makes two important hormones: thyroxin (T4) and triiodothyronine (T3). These hormones are important for growth and development, energy, and they help the heart, liver, kidneys and skin stay healthy.
The thyroid gland is told to make T4 and T3 by another hormone, which is made in the brain. This hormone is called thyroid stimulating hormone (TSH).