Norwood classifications for measuring male pattern thinning

Most people think that bald is just plain bald, but doctors measure
male pattern thinning by degrees using the Norwood classification
system. Dr. O’Tar Norwood devised this classification system in
the 1970s, answering the all-important question, “How bald am I?”
Norwood provides two classification systems, one for regular male
pattern thinning and one for Type A pattern thinning.
Regular male pattern thinning
Figure 4-1 shows the Norwood classification system for regular
male pattern thinning. Under the regular classifications, hair loss
is divided into seven patterns. Men may progress from one pattern
to the next, or they may develop any one of these patterns all at
once as the hair in that pattern thins to complete baldness in the
pattern identified on the chart.
The majority of men with pattern thinning follow the regular
pattern, with hair loss starting in the front and progressing slowly
(front and back) in two different areas (Class IV and V). On rare
occasions, a man may just bald in the crown with minimal frontal
balding (Class III Vertex). Over time, the frontal and crown areas
enlarge and merge, and the entire front, top, and crown of the head
may become bald (Class VI or VII).
Baldness in some men progresses such that they fall somewhere
between the different stages; in other men, hair loss comes to a
halt, and they remain in one stage without progressing to the next.
Although there’s no general agreement on the statistics for the fre-
quency of balding, it’s believed that advanced balding (defined as a
Norwood Class V, VI, or VII pattern) occurs in about 35 percent of
balding men.
In 95 percent of men, the
1
⁄2 inch of hair on the front of the forehead
is lost in the younger years, and the hairline recedes into a mature
male hairline (somewhere between a Class II or III pattern) with a
characteristic convex V-shape. This change from the concave juve-
nile hairline (also a typical female pattern hairline) to the convex
mature male hairline is common and not necessarily a sign of
oncoming baldness.
Balding starts at Class III in the Norwood regular classification
system (see Figure 4-1). The juvenile hairline is found in all pre-
pubertal boys, whereas a mature hairline appears in 95 percent of
Caucasian men ages 18 to 29.
Here’s an easy test to find out if your hairline is in its mature posi-
tion: Lift your eyebrows high and check the distance between the
highest crease on your forehead (in the middle) and the beginning
of your hairline:
 If your hairline touches the highest crease, it’s in the juvenile
position.
 If your hairline is
1
⁄3 to
2
⁄3 inch away from the highest crease,
it’s a mature male hairline.
 If your hairline is more than
2
⁄3 inch from the highest crease,
you have frontal balding.
A very small percentage of men keep their juvenile hairlines for
many years (former Presidents Ronald Reagan and Bill Clinton are
examples of the lucky few). Some men have a persistent forelock,
thick hair at the central front of the forehead that remains despite
pattern thinning or balding around it — like an oasis in the desert
(talk-show host David Letterman is one example). The frontal fore-
lock doesn’t appear to be subject to the ravages of DHT (refer to
the earlier section, “Hormonal influences on hair” for an explana-
tion of DHT), and the frontal hair tends to retain its thickness
much like the hair on the sides and back of the head.
Unusual genetics: There appears to be a different genetics in
some parts of the head in some people. The
2
⁄3rd inch of the juvenile
hairline and the frontal forelock have, in some people, genetics
that do not reflect the rest of the frontal part of the head. On rare
occasions, we have seen men lose all of their hair in front and on
the top except for the frontal
2
⁄3rd inch of hair (just as they had it at
the age of 12). This pattern looks strange and each man that pre-
sented with this unique pattern of balding tended to exploit the
frontal
2
⁄3rd inch by letting it grow out 6–10 inches in length to comb
back over their balding head.