Occurs when the thyroid gland secretes too much thyroxine hormone, it can speed up the body's metabolism, causing unintended weight loss and rapid or irregular heartbeats.

Treatment: a) Antithyroid drugs (propylthiouracil or metamizole) that decrease or block the effects of excess thyroid hormone. b) Radioactive iodine to destroy the thyroid and stop the excessive production of hormones. Sometimes the treatment of hyperthyroidism involves doing surgery to remove all or part of the thyroid gland.