The most commonly used classification of male hair loss is the Norwood classification. It was invented by Dr. O’tar Norwood in 1975 and outlines the most common patterns of hair loss in males suffering from androgenetic alopecia. At least 98% of males with hair loss can be categorised by using the Norwood classification.
Class I The hairline is located in the adolescent or juvenile position, which is roughly at the location of the upper brow crease. There is no balding or hair loss.
Class II The hairline sits about 1.5 centimetres farther back than during adolescence. The temporal area may also see a slight receding of the hairline. This is the mature or adult hairline location and does not indicate balding. Class III The hairline is receded around the temporal area.
Class III or class III vertex is the earliest stage of hair loss. Class III Vertex The hairline is receded at the crown of the head. Class III vertex or class III is the earliest stage of hair loss.
Class IV The temporal and vertex hair loss has increased significantly, but a thick band of hair is still separating the two balding areas.
Class V The strip of hair between the temporal and vertex areas of balding begins to break down.
Class VI The hair loss at the temporal and vertex areas have come together to form one large area of balding. The hair around the back and sides of the head remains fairly high on the scalp.
Class VII The hair loss is so extensive that only a small band of hair around the back and sides of the head remains and its positioning is low on the scalp.
Norwood Class A Men with the Norwood Class A pattern of hair loss lack the strip of hair that separates the temporal and vertex areas of balding. Men with Class A balding will experience a hairline that recedes backwards to eventually cover both the temporal and vertex area of the scalp. Eventually, the hair loss will resemble that of Class VI or VII. Class A hair loss affects less than 10% of men who suffer from androgenetic alopecia. Men with this type of hair loss tend to look balder faster because the hair loss at the front of the head is so severe. These men are good candidates for hair transplantation because the hair at the sides and back of the head remains thick and unaffected by the hair loss.