The cause of low thyroid stimulating hormone may be hypopituitarism, hyperthyroidism, and ingestion of aspirin, corticosteroids and intravenous use of heparin, etc. The harm may appear in hyperthyroidism, hypothyroidism and other diseases, affecting the health, it is recommended to seek medical treatment in a timely manner. Excessive thyroxine can negatively feedback inhibit the secretion of thyroid stimulating hormone, which leads to low thyroid stimulating hormone. Excessive thyroxine may lead to hyperthyroidism, and prolonged hyperthyroidism can lead to heart diseases such as arrhythmia, heart failure, etc., and hypermetabolic syndromes such as tachycardia, palpitations, and marked hyperactivity of the stomach and appetite, but with weight loss, and fatigue and weakness. If low thyroid stimulating hormone is present, further examination should be carried out promptly and treatment should be based on the cause.