It is a hormone secreted by the pituitary gland that promotes the growth and function of the thyroid gland. It is essentially a glycoprotein and an important indicator of normal thyroid function. Its main function is to promote the proliferation of thyroid follicular epithelial cells and the synthesis and release of thyroid hormones. The normal value of thyroid stimulating hormone is usually 0.27-4.20uIU/ml, which will not affect the body as long as it is within the normal range. When the body has hypothyroidism or pituitary hypothyroidism, thyroid stimulating hormone levels may increase, while when the body has hyperthyroidism, thyroid stimulating hormone levels may be low. Therefore, abnormal thyroid stimulating hormone levels need to be taken seriously, as they can have a significant impact on your health, whether they are too high or too low. Increased thyroid stimulating hormone levels are commonly associated with primary hypothyroidism, hypothyroidism, or exogenous thyroid stimulating hormone producing tumors. Decreased thyrotropin levels, on the other hand, are mainly caused by diseases such as pituitary hypothyroidism and non-thyrotropic hormone tumors. Thyroid stimulating hormone is very important to the human body, so it is best to have thyroid stimulating hormone levels measured once a year, and if any abnormalities are found, they need to be treated promptly and symptomatically.