What are the causes of gray hair?

Normal people will gradually grow grey hair as they get older, as physiological grey hair.
Some patients with genetic diseases, such as albinism, are accompanied by grey hair; some other diseases may also lead to grey hair, such as hyperthyroidism, vitiligo and recovery from baldness; and some patients have grey hair associated with the use of drugs that affect tyrosinase function or nutrient deficiencies in the body.