In the 1970’s Dr . O’tar Norwood developed a now widely used method of evaluating the degrees of male pattern baldness known as the Hamilton/Norwood Scale. He delineated between two kinds of pattern balding—regular male pattern balding and type A pattern balding. Each type has unique characteristics. Regular male pattern balding occurs in the majority of males, while type A male pattern balding occurs in less than 10% of patients.
Regular male pattern balding is divided into seven unique stages of loss. Often hair loss will advance steadily from one stage to the next, but, sometimes, hair loss can progress rapidly into sudden complete baldness. It’s important to note that some men may not fit the scale well and this is not a cause for concern. The scale is only an imperfect guide.
This type of balding begins at the front of the head and proceeds slowly in two different areas—at the forehead and the crown as in Classes IV and V. Next, over time the frontal and crown bald patches enlarge and the entire front, top, and crown go bald as in Class VI and VII. Some lucky men only bald lightly as in Class III Vertex.
No need to become fatalistic, though, because some men remain in one stage and never develop further balding. Another ray of hope is that it’s believed that only 35% of balding males ever reach the more virile or robust hair loss common to Classes V, VI, and VII.
each stage of balding typically refers to a different stage of life or age of the sufferer. Juvenile hair loss of 1/2 inch on the front of the forehead occurs in 95% of males as seen in Class II. Between Class II and III we find the fortunate men who experience a loss, characteristic of the mature male hairline, which does not mean that serious balding will emerge. In fact 95% of Caucasian men between 18-29 years develop this amount of loss and never bald further. This stage of balding takes on a convex V-shape line.
Type A pattern thinning is far less common than regular pattern thinning occurring in only 10% of men. Typically, type A is identified by loss that begins at the forehead and progresses toward the back of the head. Unfortunately, these men appear bald because of the significant frontal loss. There are four stages of loss with this type of balding as the hairline recedes over the crown.