Hair
loss usually develops gradually and may be patchy or diffuse
(all over). Roughly 100 hairs are lost from your head every
day. The average scalp contains about 100,000 hairs.
Each
individual hair survives for an average of 4-1/2 years,
during which time it grows about half an inch a month.
Usually in its 5th year, the hair falls out and is replaced
within 6 months by a new one.
Genetic
baldness is caused by the body's failure to produce new
hairs and not by excessive hair loss.
Both
men and women tend to lose hair thickness and amount as they
age. Inherited or "pattern baldness" affects many more men
than women. About 25% of men begin to bald by the time they
are 30 years old, and about two-thirds are either bald or
have a balding pattern by age 60.
Typical
male pattern baldness involves a receding hairline and
thinning around the crown with eventual bald spots.
Ultimately, you may have only a horseshoe ring of hair
around the sides. In addition to genes, male-pattern
baldness seems to require the presence of the male hormone
testosterone.
Men who
do not produce testosterone (because of genetic
abnormalities or castration) do not develop this pattern of
baldness.
