Low serum thyroid stimulating hormone is a sign of hyperthyroidism and requires medication for hyperthyroidism. It usually takes one to two years of treatment. During the period of taking medication, the patient should have regular recheck of thyroid function, liver function, blood count and thyroid ultrasound. There are two types of anti-thyroid drugs commonly used: methimazole and propylthioxypyrimethamine. Surgery is required for obvious enlargement of the thyroid gland, or if malignancy is highly suspected. Patients who cannot be easily controlled by medication or who have relapsed after treatment can be treated with radioactive iodine.