Subclinical hypothyroidism is the abbreviation of subclinical hypothyroidism. The hazards of subclinical hypothyroidism include: causing dyslipidemia, promoting the occurrence and development of atherosclerosis, and developing into clinical hypothyroidism. 1. Leading to dyslipidemia: It is found that the total cholesterol level of patients with subclinical hypothyroidism is higher than that of patients with normal thyroid function, and the incidence of hypercholesterolemia is higher than that of normal people, which is positively correlated with the level of thyroid-stimulating hormone. Levothyroxine replacement therapy can reduce serum total cholesterol and LDL cholesterol levels in patients with subclinical hypothyroidism. 2. Promote the occurrence and development of atherosclerosis: subclinical hypothyroidism is an independent risk factor for ischemic heart disease, as are hypertension, dyslipidemia, and hyperglycemia, which can cause cardiac function abnormalities. 3. Development of clinical hypothyroidism: Studies have shown that subclinical hypothyroidism may develop into clinical hypothyroidism. The annual incidence of developing clinical hypothyroidism is 2%, 3% and 5% for thyroid autoantibody-positive alone, subclinical hypothyroidism alone and thyroid autoantibody-positive combined with subclinical hypothyroidism respectively. Patients with subclinical hypothyroidism should seek prompt medical attention.