Male Baldness
Hair loss can start in different areas but is usually at the temples and/or on the crown of the head. Initial thinning of hair progresses over a number of years and may lead to total baldness but more typically loss of hair over the top surface of the head.
Hamilton and later Norwood have classified the patterns of male pattern baldness. Although the density of hair in a given pattern of loss tends to diminish with age, there is no way to predict what pattern of hair loss a young man with early male pattern baldness will eventually assume. In general, those who begin losing hair in the second decade are those in whom the hair loss will be the most severe. In some men, initial male-pattern hair loss may be delayed until the late third to fourth decade. It is generally recognized that men in their 20’s have a 20 percent incidence of male pattern baldness, in their 30’s a 30 percent incidence of male pattern baldness, in their 40’s a 40 percent incidence of male pattern baldness, etc. Using these numbers one can see that a male in his 90’s has a 90 percent chance of having some degree of male pattern baldness.
There are seven levels of loss in the Norwood scale:
Norwood 1
Normal head of hair with no visible hair loss.
Norwood 2
The hair is receding in a wedge-shaped pattern.
Norwood 3
Same receding pattern as Norwood 2, except the hairline has receded deeper into the frontal area and the temporal area.
Norwood 4
Hairline has receded more dramatically in the frontal region and temporal area than Norwood 3 and there is the beginnings of a bald spot at the back of the head.
Norwood 5
Same pattern as Norwood 4 but much reduced hair density.
Norwood 6
The strip of hair connecting the two sides of the head that existed in Norwood 4 and 5 no longer exists in Norwood 6.
Norwood 7
Norwood 7 shows hair receding all the way back to the base of the head and the sides just above the ears.
The term "common baldness" usually means male-pattern baldness, or permanent-pattern baldness. Male-pattern baldness is the most common cause of hair loss in men. Men who have this type of hair loss usually have inherited the trait. Men who start losing their hair at an early age tend to develop more extensive baldness. In male-pattern baldness, hair loss typically results in a receding hair line and baldness on the top of the head.