Hyperthyroidism is caused by an excess of thyroid hormones in the patient’s blood, which abnormally stimulates multiple tissues and organs in the body. The clinical manifestations of hyperthyroidism vary from patient to patient due to individual differences in the extent of the disease, age of onset, gender and responsiveness to abnormal thyroid hormones. The most common clinical manifestations of hyperthyroidism include: fear of heat, excessive sweating or warm and moist skin; irritability or mood swings, insomnia; panic attacks and weakness; easy to eat but weight loss; increased frequency of stools; protruding eyes in half of the patients, either double or single, sometimes accompanied by congestion and edema; and scanty menstruation or even amenorrhea in women. In elderly patients, these manifestations are not obvious. Some patients have obvious enlargement of the thyroid gland in the neck, and in severe cases, the entire neck may be enlarged and vascularized. A few patients have mucinous edema of the skin of the lower extremities or diffuse mucosal pigmentation. A few patients also develop vitiligo-like changes in the skin. Patients with long term untreated hyperthyroidism may develop hyperthyroid heart disease, psychiatric disease or combined with diabetes mellitus and skin disease.