Hyperthyroidism may cause severe mitral regurgitation. If hyperthyroidism is not timely standardized treatment, excessive thyroid hormone will act on the heart muscle, causing myocardial contractility, but also cause peripheral vasodilatation, compensatory increase in cardiac output, if the long-term progress of the left ventricle can be caused by compensatory enlargement, which will lead to mitral regurgitation, and in severe cases, the development of severe regurgitation. Therefore, it is possible for hyperthyroidism to cause severe mitral regurgitation. Once the diagnosis of hyperthyroidism is confirmed, timely and standardized treatment with antithyroid drugs such as propoxythiazide, iodine radiation therapy or surgery should be used to maintain thyroid hormone levels within a reasonable range and to avoid the occurrence or progression of complications. Patients diagnosed with hyperthyroidism who develop severe mitral regurgitation are advised to go to the hospital and ask the doctor to make a judgment and clarify the cause of the disease.