The reasons for the decrease and disappearance of the crescent teeth are closely related to both certain diseases and physical factors. The decrease of the crescent is firstly related to thyroid disease, when the hypothyroid gland is not producing enough thyroid hormones, the hormones are closely related to the health of the skin, the appendages and the nails. Hypothyroidism can cause a significant reduction or disappearance of the nail crescents, and the nutritional status of the skin, especially the nails, can be improved through treatment. Some people have irregular work and life, excessive stress, partiality, picky eating, and eat less fresh vegetables, fruits, and whole grains, resulting in an obvious lack of vitamins, minerals, and trace elements in our body. By eating a well-balanced diet to achieve a therapeutic effect, often the nail crescents will be significantly reduced and clearer. Age factors, aging is also the cause of nail crescent reduction, but age is impossible to change, through a scientific lifestyle, to slow down the aging of the age of the situation, reasonable and balanced nutrition, less oil, less salt, less sugar, eat more fresh vegetables, fruits, meat, eggs, milk to moderate, moderate amount. To pay attention to the science of exercise step by step, to help reduce psychological stress, while improving cardiorespiratory function, quit smoking and limit alcohol. At the same time, regular work and rest, adequate sleep, psychological balance is equally important. There is a clear correlation between the disappearance or decrease of the crescent moon and thyroid disease, nutrition and aging.