Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. The main indicator of this condition is the elevator level of thyroid hormones T3 and T4 as well as lower values of TSH. The most common cause and 70 to 80% of cases is Graves' disease. Signs and symptoms vary between people and may include irritability, muscle weakness, sleeping problems, a fast heartbeat, heat intolerance, diarrhea, enlargement of the thyroid, hand tremor, and weight loss. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism. There are three main treatment options: radioiodine therapy, medications, and thyroid surgery. Medications such as beta blockers may control the symptoms, and anti-thyroid medications such as methimazole may temporarily help.