Hyperthyroidism

Hyperthyroidism, also known as "overactive thyroid" is a disease that causes the thyroid gland to secrete too much thyroid hormone into the body. The thyroid gland, and its hormones, are responsible for controlling the body's metabolic rate.

The most common symptoms of hyperthyroidism are nervousness and irritability, inability to gain weight, and thin, brittle hair. The most common cause of hyperthyroidism is Grave's disease, a condition that causes the thyroid gland to swell and over-secrete hormones.