Basic Facts About Hair Loss

Although both men and women can suffer significant hair loss, over 50% of men will suffer with Male Pattern Baldness (MPB), also known as androgenetic alopecia, at some point in their lives.  The reason behind hair loss is a genetically inherited sensitivity to Dihydrotestosterone (DHT) and 5-alpha-reductase. The enzyme 5-alpha-reductase converts testosterone, a male hormone, to DHT, the substance identified as the end-cause for hair loss.

Most hair loss follows a pattern that has been codified in a table called the Norwood Scale (see figure 1). There are seven patterns of hair identified in the Norwood Scale, Norwood I being a normal head of hair with no visible hair loss, Norwood II showing the hair receding in a wedge-shaped pattern. Norwood III shows the same receding pattern as Norwood II, except the hairline has receded deeper into the frontal area and the temporal area.

Type IV on the Norwood Scale indicates a hairline that has receded more dramatically in the frontal region and temporal area. Additionally there is a balding area at the very top center of the head, but there is a bridge of hair remaining between that region and the front.

Type V on the Norwood Scale shows that very same bridge between the frontal region and the top center, also called the vertex, beginning to thin. Type VI on the Norwood Scale indicates that the bridge between the frontal region and the vertex has disappeared.

Finally, Type VII on the Norwood Scale shows hair receding all the way back to the base of the head and the sides just above the ears. Norwood patterns are determined genetically.  

Figure 1: Norwood scale