Graves disease or hyperthyroidism is a condition that causes your thyroid gland to make too much thyroid hormone, or become overactive.

The thyroid gland is located in the neck and is shaped like a butterfly. There are several hormones made by the thyroid gland that are important for growth and development. These same hormones also help with your energy level and  help the heart, liver, kidneys and skin work correctly. These important hormones are called thyroxin (T4) and triiodothyronine (T3). 

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).

The most common cause of hyperthyroidism is Graves disease.  There are other less common causes of hyperthyroidism. Your doctor can discuss these causes with you.

Graves disease is more common in teenage girls, but can be found in boys and girls of any age.