Thyroid hormone is an important hormone normally secreted by the human body, it is a hormone that exists in normal human beings, and it can regulate the growth and development of the body, metabolism, promote the process of heat production, and promote the development of the bones and the nervous system, so the thyroid hormone itself does not have any harmful effects on the body. However, over or under secretion of thyroid hormone concentration can cause metabolic diseases and even affect growth and development. Excessive thyroid hormone can form hyperthyroidism, which manifests itself in hypermetabolic symptoms such as fear of heat, excessive sweating, palpitations, weight loss, hyperphagia, and easy hunger. Decreased secretion of thyroid hormone in adults can cause hypothyroidism, manifested by fear of heat, little or no sweat, swelling, weight gain and other low metabolic symptoms, in children can cause cretinism, which not only affects height and physical development but also affects neurological development, maternal hypothyroidism during pregnancy can also affect the neurological development of the fetus.