We have previously mentioned that hyperthyroidism can induce cardiovascular system diseases such as heart failure and arrhythmias, with atrial arrhythmias such as atrial fibrillation and occasionally atrioventricular block being the most common. Therefore, when patients present with atrial arrhythmias such as atrial fibrillation, attention should be paid to the screening of hyperthyroidism. People may ask if hyperthyroidism can cause arrhythmias, so when hypothyroidism occurs, can arrhythmias also occur? The answer is yes, and today we will give you a brief overview of arrhythmias associated with hypothyroidism. Hypothyroidism, or hypothyroidism for short, is a clinical syndrome caused by a deficiency of thyroid hormones due to different causes, resulting in a decrease in the body’s metabolism and the function of various systems throughout the body. Patients generally present with easy fatigue, fear of cold, weight gain, memory loss, unresponsiveness, drowsiness, mental depression, and muscle cramps. Physical examination reveals indifferent expression, pallor, dry, rough and flaky skin, edema of the skin of the face, eyelids and hands, and sparse hair. Hypothyroidism can induce multi-system diseases such as mental system, skeletal and muscular, cardiovascular system, respiratory system, endocrine system, digestive system, and hematological system. The effects of hypothyroidism on the cardiovascular system are mainly manifested as reduced cardiac output, enlarged turbinate and low heart sounds, and pericardial effusion on ultrasound examination. Long-term patients are prone to complications of coronary heart disease due to increased blood cholesterol. In terms of arrhythmia, the ECG of hypothyroid patients mainly shows low voltage, sinus bradycardia, atrioventricular block, and low or inverted T waves. In a small number of patients, the electrocardiogram may show a long QT syndrome, leading to tip-twist ventricular tachycardia. In addition, hypothyroidism has been reported to cause atrial fibrillation as well. Overall, hypothyroidism causes mainly slow arrhythmias and occasionally tachyarrhythmias in patients. Hypothyroidism is often controlled with thyroid hormone replacement therapy, and the arrhythmia may be reduced or recovered. Through the contents of this article, we hope that you will realize that arrhythmias are often accompanied by other systemic diseases. Therefore, while treating arrhythmias, it is important to pay attention to the presence of other systemic diseases and to improve the relevant tests to investigate the root causes.