Hypothyroidism can be life-threatening. Hypothyroidism is a group of hypometabolic syndromes caused by low concentrations of thyroid hormones in the blood. Typical hypothyroidism is characterized by a fear of cold, little or no sweating, swelling of the face and eyelids, loss of muscle strength, unresponsiveness, weight gain, and other hypometabolic symptoms. Severe hypothyroidism can hypothyroidism for the following reasons: i. Hypothyroidism can lead to slow heart rate and even arrhythmia in patients, and can also lead to pericardial effusion, and severe pericardial effusion and heart rate arrhythmia can hypothyroidism. Second, severe hypothyroidism is not effectively treated for a long time, and mucus edema coma may occur under infection, surgery, anesthesia and other triggers, and mucus edema coma can be life-threatening. Hypothyroidism requires long-term replacement therapy with levothyroxine sodium. As long as the replacement dose is reasonable, the prognosis for hypothyroidism is good and the treatment drug itself has no side effects.