The effects of thyroid hormones are as follows: First, to promote growth and development. The most obvious period for thyroid hormones to promote growth and development is during infancy, and the impact is greatest in the first five months after birth. It mainly promotes the growth and development of bones, brain and reproductive organs. In the case of thyroid hormone deficiency, congenital or juvenile thyroid deficiency may occur, leading to cretinism. Patients with cretinism are short in stature and have impaired mental development. The second effect is on metabolism. Thyroid hormones increase the oxygen consumption of most tissues and increase the thermogenic effect. The third one is the effect on the metabolism of three major nutrients: carbohydrates, fats and proteins. Under normal circumstances, it can promote protein synthesis, especially protein synthesis of bone, skeletal muscle and liver increases significantly. In other aspects, thyroid hormones also have important effects on other organs, such as maintaining the excitability of the nervous system and acting on the heart muscle to produce positive inotropic effects.