The thyroid gland is an important endocrine gland in the human body. The thyroid gland mainly secretes thyroid hormones, the role of thyroid hormones is mainly to promote metabolism, promote human growth and development and energy metabolism, so too much or too little thyroid hormones can affect the heart. The main manifestations are: a. When there is too much thyroid hormone, that is, when hyperthyroidism occurs, the main manifestations are accelerated heart rate, increased blood pressure and enhanced myocardial contraction, and in serious cases, hyperthyroid heart disease can occur, manifesting as premature ventricular beats, atrial fibrillation and other arrhythmias, and even heart enlargement and heart failure. Second, when there is too little thyroid hormone, that is, hypothyroidism occurs. Hypothyroidism will slow down the heart rate, lower blood pressure and weaken the contraction of the heart muscle, which can produce pericardial effusion and affect the contractile function of the heart. Third, when severe hyperthyroidism occurs in thyroid crisis, or severe hypothyroidism occurs in mucinous edema coma, it has a greater impact on the heart, and can even occur in cardiac arrest.