The normal range of thyroid stimulating hormone (TSH) is 0.35 to 5.5μIU/ml. Due to the different testing methods and reagents, the reference indexes of each hospital are different and need to be analyzed specifically. Thyroid stimulating hormone is a hormone secreted by the pituitary gland, which promotes the growth of thyroid cells and the secretion of thyroid hormone. Thyrotropin is regulated by thyrotropin-releasing hormone from the hypothalamus and also by thyroid hormones. Thyrotropin is one of the most sensitive indicators of thyroid function. Free thyroxine and free triiodothyronine are often measured together to diagnose thyroid function. Any abnormal increase or decrease in thyroid stimulating hormone value should be taken seriously and actively consult a doctor for diagnosis and treatment.