Hyperthyroidism happens when the thyroid gland makes too much thyroid hormone. This condition also is called overactive thyroid. Hyperthyroidism speeds up the body's metabolism. That can cause many symptoms, such as weight loss, hand tremors, and rapid or irregular heartbeat. Several treatments are available for hyperthyroidism. Anti-thyroid medicines and radioiodine can be used to slow the amount of hormones the thyroid gland makes. Sometimes, hyperthyroidism treatment includes surgery to remove all or part of the thyroid gland. In some cases, depending on what's causing it, hyperthyroidism may improve without medication or other treatment.