Hyperthyroidism is mostly seen in women. Excess thyroid hormone can cause a series of clinical manifestations, such as fear of heat, excessive sweating, hyperphagia, weight loss, panic attacks, emotional stress and irritability. Most patients with hyperthyroidism have an enlarged thyroid gland. The degree of enlargement varies from mild to severe, and very few patients with hyperthyroidism do not have an enlarged thyroid gland. Many patients with hyperthyroidism also have protruding eyes, the degree of which may vary from mild to severe. Thyroid function tests may reveal an increased rate of 131I uptake by the thyroid gland and significantly higher levels of thyroid hormones in the blood. The most common type of hyperthyroidism is toxic diffuse goiter, which accounts for about 80% of all hyperthyroid patients. Its etiology is mainly related to immune dysfunction and congenital inheritance.