Smoking increases the risk of atherosclerosis and lipid metabolism disorders in people with hypothyroidism. In hypothyroidism, insufficient levels of thyroid hormones can lead to a series of systemic symptoms, including elevated blood lipids, and smoking may increase triglyceride and total cholesterol levels, lower HDL levels, and aggravate lipid metabolism disorders. Moreover, smoking will have a synergistic effect with hyperlipidemia, accelerating the formation of atherosclerosis, which may induce cardiovascular disease and cerebrovascular disease in further development. In addition, smoking also increases the risk of bladder cancer and lung cancer. Patients diagnosed with hypothyroidism should quit smoking in time to avoid the harmful effects of smoking and maintain a healthy lifestyle under the guidance of a doctor.