It is the most serious complication of hyperthyroidism, with a mortality rate of 60% to 80%. The elderly are particularly at risk. In the case of uncontrolled hyperthyroidism, stressful stimuli, such as severe infections, trauma, surgery, etc., are the most common triggering factors, in the hyperthyroidism is not fully controlled for surgery or severe hyperthyroidism patients for 131 iodine radiation therapy did not take the necessary measures, can also lead to the occurrence of hyperthyroidism crisis. 1, pathogenesis: the occurrence of hyperthyroid crisis may be caused by a variety of factors: 1) a large number of thyroxine release into the blood circulation; 2) the increase of free thyroxine in the blood; 3) the body’s response to thyroid hormone abnormality; 4) the increase of adrenergic energy; 5) the decrease of thyroid hormone clearance in the liver. 2, clinical features: diffuse and nodular goiter caused by hyperthyroidism can occur crisis. Typical clinical manifestations are high fever, profuse sweating, tachycardia, frequent vomiting and diarrhea, delirium, and even coma and shock. Electrolyte imbalance and ultimately respiratory and circulatory failure and death. Goiter is evident in most patients. Elderly patients may only have cardiac abnormalities, especially arrhythmia or gastrointestinal symptoms as prominent manifestations. Most of the patients can find out the obvious cause of the disease. 3, the principle of treatment: 1) to protect the organs of the body, to prevent functional failure: fever is mild, use antipyretic. A large amount of aspirin should be avoided, because it can make the patient’s metabolic rate further increase, and also can compete with thyroid hormone for thyroid binding protein to increase free hormone. In cases of hyperthermia, aggressive physical hypothermia and artificial hibernation if necessary. Oxygen should be administered due to the marked increase in metabolism. Due to high fever, vomiting and profuse sweating, water supplementation, correction of electrolyte disorders, sugar and vitamin supplementation are required. Apply corticosteroid therapy. (2) Reduce circulating thyroid hormone level: after oral or gastric tube nasal feeding of large doses of thiourea antithyroid drugs (propylthiouracil 600~1000mg/d or methimazole 60~100mg/d), it can rapidly (within 1h) prevent the organic binding of iodide in the thyroid gland. Maintenance doses are given later. The administration of iodide (30 drops of compound iodine solution, or 3 to 4 ml/d of compound iodine solution by sedation) started 1 h after the administration of thioureas can more completely inhibit the production of additional thyroid hormones produced by the iodine used. 3) Reduce the response of peripheral tissues to thyroid hormone: Anti-sympathetic drugs can reduce the action of peripheral tissues to catecholamines. Commonly used are propranolol (orally every 6h, 40-80mg per day; or sedation 1-5mg), reserpine and quetiapine. 4）Control of triggers: Actively deal with various disease triggers of crisis, including the application of antibiotics to treat infections. Prognosis: The first 3 days after the start of treatment is the key moment of rescue. If the treatment is successful, the patient mostly improves within 1 to 2 days after treatment and recovers within 1 week. After recovery from the crisis, iodine and corticosteroids can be tapered.