The main reasons for the growth of hair on the chest are the following: First, consider the genetic factors, parents hairy, the next generation will also appear hairy may also produce hair on the chest, which is the performance of the human androgen bias, is a normal phenomenon. The endocrine disorder is mainly due to pituitary tumor or other causes of pituitary secretion abnormalities, so that androgen hormone changes, or due to the growth of liver inactivation estrogen level, androgen bias caused by. Third, genetic diseases are considered, such as Fernando syndrome, in which the patient has a hairy body and a tendency to violence. Fourth, it is caused by the use of drug factors, such as isoniazid. These are all pathological conditions and should be promptly seen.