Hyperthyroidism is a chronic metabolic disease, a group of hypermetabolic syndromes dominated by increased concentrations of thyroid hormones in the blood. Hyperthyroidism involves various systems throughout the body, such as the cardiovascular system, skeletal-motor system, genitourinary system, and digestive system, etc. Severe hyperthyroidism can kill people. The causes of death due to hyperthyroidism are as follows: i. Severe hyperthyroidism can be complicated by hyperthyroid heart disease, leading to arrhythmia, heart enlargement and heart failure, and severe heart failure can lead to cardiac arrest of patients. Severe hyperthyroidism is prone to complicate hyperthyroid crisis. Severe hyperthyroidism can induce hyperthyroid crisis when triggered by infection, pregnancy, surgery, etc. The mortality rate of hyperthyroid crisis is extremely high. Third, severe hyperthyroidism will affect the blood routine, causing white blood cell reduction and even granulocyte deficiency. Granulocyte deficiency can lead to serious uncontrollable infections in the organism, resulting in death from infectious toxic shock. Fourth, severe hyperthyroidism can cause serious liver damage, and severe liver damage may also lead to death of the patient.