Men with severe hair loss on the top of the head consider seborrheic alopecia, baldness and other diseases caused. 1. seborrheic alopecia: seborrheic alopecia is also called androgenic alopecia, the main cause of this hair loss is heredity, mainly due to the high level of androgens in the body is converted into dihydrotestosterone, which will make the hair follicle miniaturized, the hair in the anagen phase gradually thin, so that the original thick black hairs become thin and light, and ultimately lead to the disappearance of the hair follicle atrophy, the hair fall off. 2. Patch baldness: Patch baldness refers to sudden and limited patchy hair loss, the cause of which is not particularly clear, and is considered to be related to autoimmunity, heredity, neuropsychiatric factors, endocrine disorders, and so on. Boys with serious hair loss on the top of the head, it is recommended to go to the hospital in time, to clarify the type of hair loss, standardized treatment under the guidance of the doctor.