Low TSH, i.e. low thyrotropic hormone, is harmful to different diseases and may lead to endocrine disorders, stunted growth or even induce cardiovascular diseases. TSH belongs to a kind of pituitary gland secretion of prohormone, is an important hormone to regulate the thyroid hormone, if TSH is too low there may be primary hyperthyroidism, there may be pituitary hypothyroidism. Primary hyperthyroidism will affect endocrine disorders, resulting in irregular menstruation or even amenorrhea in women and impotence in men; it will affect the cardiovascular system, resulting in palpitations, arrhythmia, hyperthyroidism heart disease, etc.; it will affect the digestive system, resulting in increased appetite, diarrhea, weight loss and other symptoms. Pituitary hypothyroidism will lead to a decrease in the secretion of thyroid hormones, which will lead to short stature and incomplete development of the nervous system in children; and bradycardia, facial swelling, apathy and loss of appetite in adults. In case of low TSH, it is recommended that the patient should actively seek medical advice and follow the doctor’s instructions for treatment.