Hyperthyroidism is a condition where the thyroid gland produces too much thyroid hormone, also known as an overactive thyroid. The thyroid gland is a small, butterfly-shaped gland located in the front of the neck that produces hormones that control the bodys metabolism. The most common cause of hyperthyroidism is Graves disease, an autoimmune disorder where the immune system attacks the thyroid gland, causing it to produce too much thyroid hormone. Other causes of hyperthyroidism include overactive thyroid nodules, inflammation of the thyroid gland, too much iodine, and taking too much thyroid hormone medicine. Risk factors for hyperthyroidism include a family history of thyroid disease, certain chronic illnesses, and recent pregnancy. Symptoms of hyperthyroidism can vary from person to person but may include weight loss, rapid or irregular heartbeat, nervousness, irritability, trouble sleeping, fatigue, and others. If left untreated, hyperthyroidism can lead to complications such as heart problems, thinning bones, and menstrual cycle and fertility issues.