Androgens and pattern baldness
In a world where personal appearance is constantly gaining
importance, hair loss can be a very serious condition for both
men and women. In order to regulate the growth of hair in certain
areas of the body, a solid understanding about what causes hair
loss can be extremely helpful. This research has been initiated
by a team of scientists who have recently discovered some very
interesting facts about hair loss.
Scientists have determined that one of the most important elements
in the growth process of hair is the activity of androgens in
the body. Androgens are male sex hormones that promote the development
and maintenance of male sex characteristics in the body. One
of these characteristics is hair growth. The major androgen
in the body is known as "testosterone" but another
important androgen is also known as "dihydrotestosterone" or
DHT. DHT is made from testosterone by enzymes called 5 alpha
reductase.
Scientists have recently discovered that, our body hair is dependant,
at least in part, upon the presence of androgens. For most body
hair follicles, androgens stimulate their growth activity and
make small vellus hair follicles into larger terminal hair follicles
that produce bigger hair fiber. In contrast, hair follicles
on our scalp do not need androgens to grow into large terminal
scalp hair follicles. Some scalp hair follicles have no significant
response to androgens (mostly those follicles at the back of
our scalps), but other scalp hair follicles (mostly limited
to hair follicles on the top of our scalps) may actually start
to miniaturize and even disappear when certain androgens become
active! Body hair will grow when there are androgens in the
body but scalp hair sometimes won't! This is a paradoxical fact
about androgens that has had scientists "scratching their
heads" for answers. Why should body hair follicles increase
their growth while scalp hair follicles reduce their growth
in response to the exact same androgen hormones?
It is common knowledge to most people that women almost always
have a low level of testosterone in their bodies. Men, however,
generally have a lot more testosterone than women. Since scalp
hair does not need androgens to be present for hair growth to
occur, women usually have just as much hair on their heads as
men and often more! Scalp hair, it seems, will grow regardless
of the presence of androgens in the body. Certain androgen activity,
however, may also contribute to male pattern baldness.
This paradoxical fact about androgens was examined more closely
through a controlled study of both men and women. This test
was done through the introduction of a drug called Finasteride
into the body. It was administered to both men and women and
the results were astounding. When Finasteride was given to
men who had suffered from scalp hair loss, the men showed
a marked
improvement in the growth of their scalp hair. When Finasteride
was given to women with scalp hair loss, there was no improvement.
From these results, scientists concluded that male pattern
hair loss and female pattern hair loss were completely different
conditions and they were based on completely different circumstances.
Of course, many people already know that male pattern baldness
is different from female pattern baldness just from the typical
age at which the sexes seem to acquire the condition. Men seem
to go bald at an earlier age than women, usually in their 30's
and 40's. Women, however, usually don't start to show signs
of baldness until they are in their 50's. Men also tend to go
completely bald whereas women usually show just a marked thinning
of their hair. These obvious differences were made a lot clearer,
however, through scientific studies.
The truth about androgens was studied in even more detail after
the discovery was made that Finasteride could positively affect
male pattern baldness but not affect female pattern baldness.
Scientists wanted to know "What's going on here?" In
the test, Finasteride was also referred to as a "type 2
5 alpha Reductase inhibitor". Finasteride was an "inhibitor" because
it actually slowed down the production of the enzyme known as "type
2 5 alpha Reductase". This is one form of the enzyme that
converts testosterone into DHT. By examining the effects of
this slow down on enzyme activity, more conclusions were drawn.
By slowing down the production of the "type 2 5 alpha Reductase" enzyme
in the body, Finasteride slowed down another process that normally
took place in the body. This drug Finasteride was really having
quite an effect! The process that was slowed by Finasteride
was the process of testosterone being converted into DHT. Remember
testosterone is the primary androgen in the body and DHT is
another important androgen that comes about when testosterone
is converted. Scientists thought that the conversion of testosterone
into DHT was what eventually leads to Male pattern baldness.
They found that they could stop the baldness from happening
by inhibiting the "type two 5 alpha Reductase" enzyme
and thereby stopping the DHT from forming in the body. This
conclusion turned out to be true.
The problem is a bit more complicated than just having too much
DHT in the body, but scientists were certainly well on their
way to a new treatment for male pattern baldness. It still had
to be explained by scientists that men who acquired male pattern
baldness also had a genetic predisposition that contributed
to the condition. In fact, the presence of DHT had to occur
in combination with another factor; that of having hair follicles
that were oversensitive to androgen activity. If the men had
a genetic predisposition to be oversensitive to androgen activity,
then the DHT would always adversely affect their hair growth.
One molecule of DHT actually has five times the androgen activity
in the body as one molecule of testosterone. Androgen activity
has a positive affect on body hair, but a negative effect on
scalp hair in many men with the genetic disposition to androgen
oversensitivity. As long as testosterone is being converted
into DHT, this increase in androgen activity will come about
and those with the genetic disposition to male baldness will
start to lose their hair. This DHT formation is helped along
by the presence of the enzyme "type 2 5 alpha Reductase" so,
as scientists had originally theorized, the "type 2 5 alpha
Reductase" enzyme had to be stopped!
Men have been lucky in that the treatment of Male pattern baldness
has been extremely successful through the use of the "type
2 5 alpha Reductase inhibitor" Finasteride. Women have
not been as lucky as men. Scientists have still not been able
to clearly determine what causes female pattern baldness. These
two conditions are very different and female pattern baldness
will need more study in order to determine a successful treatment.
Androgens and pattern baldness references
- Kaufman KD.
Androgens and alopecia.
Mol Cell Endocrinol. 2002 Dec 30;198(1-2):89-95. PMID: 12573818
- Shapiro J, Kaufman KD.
Use of finasteride in the treatment of men with androgenetic
alopecia (male pattern hair loss).
J Investig Dermatol Symp Proc. 2003 Jun;8(1):20-3.
PMID: 12894990
- Kaufman KD, Dawber RP. Finasteride,
a Type 2 5alpha-reductase inhibitor, in the treatment of men
with androgenetic alopecia. Expert Opin Investig Drugs. 1999
Apr;8(4):403-15.
PMID: 15992088
- Kaufman KD.
Androgen metabolism as it affects hair growth in androgenetic alopecia.
Dermatol Clin. 1996 Oct;14(4):697-711.
PMID: 9238328
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