In order for this type of hair loss to occur, two conditions must be present: a genetic predisposition of the hair follicles to stop growing at a specific age, which is inherited from either one or both parents, and the presence of dihydroxytestosterone (DHT), a male hormone that occurs naturally in the scalp.
This type of hair loss develops in specific patterns as seen in the accompanying illustration. Notice that even in the most severe cases (Type 7) the hair on the back and side of the head is still retained. This is the permanent donor hair that is used for hair transplantation. It may be helpful to compare your own type of hair loss with these classifications as well as with Dr. Cohen’s patients shown elsewhere on the website.