This refers to the surplus production of a hormone (thyroxine) by the butterfly-shaped gland in the neck (thyroid). Hyperthyroidism is a condition in which an overactive thyroid gland is producing an excessive amount of thyroid hormones that circulate in the blood. “Hyper” means “over” in Greek). Thyroid hormones include thyroxine (T4) and triiodothyronine (T3). T3 is actually the most active thyroid hormone. Much of the T4 is converted to T3 in the bloodstream. As such, it is also called the OVERACTIVE THYROID. Normally, the rate of thyroid hormone production is controlled by the brain from the pituitary gland, which is in turn regulated by the hypothalamus.
The statistic shows that in more than 70% of cases, hyperthyroidism is caused by Graves' disease and can be associated with an eye disease (Graves' ophthalmopathy). Normally, the immune system helps protect your body against viruses, bacteria, and other substances. The autoimmune disease causes it to attack your body's tissues and/or organs. With Graves' disease, the immune system stimulates your thyroid, making it produce too much hormone. Doctors think Graves' disease may run in families. It is most common among young women.

Hyperthyroidism is associated with so many signs and symptoms, however, People at the age of 70 and older may not have any symptoms and signs of hyperthyroidism. In general, the symptoms become more obvious as the degree of hyperthyroidism increases. The symptoms usually are related to an increase in the metabolic rate of the body.