There
are many causes of hair loss in men and women, including
disease, nutritional deficiency, hormone imbalance, and
stress. However, by far the most common cause is what is
called adrogenetic alopecia. Alopecia is simply the medical
term for hair loss. Androgenetic refers to the fact that
both a genetic predisposition to balding, and the influence
of androgens, or male hormones, play a part in this type
of hair loss.
In fact, there is a third factor, which is the passage of
time, or aging. In other words, in order for androgenetic
alopecia to occur, there must be:
* a genetic propensity for balding
* the presence of androgens, or male hormones
* enough aging time to allow the first two factors to exert
their influence on the hair folliclesGenetics
Genetics is not always simple, and such is the case with
balding. Just the presence or absence of balding in one’s
parents or grandparents, on either the mother’s or
father’s side, is not necessarily predictive of one’s
likelihood of balding. Certainly, if a man’s father
is completely bald, and this man begins to rapidly lose
hair in his early twenties, it’s a safe bet that he
will develop extensive balding at some point. In short,
it’s very hard to accurately predict who will go bald
and how rapidly.
This inherent uncertainly about the progression of balding
is of utmost importance in planning surgical hair restoration,
as we will see in later sections. We must always plan for
a "worst case scenario" in order to give patients
the best possible results in the long term, as well as in
the short term. Anything less is irresponsible.
Androgenic Hormones
All normal men and women produce "male" hormones.
The most common of these are testosterone, androsteinedione,
and dihydrotestosterone (DHT). Androgens are produced by
the testicles and adrenals in men, and by the ovaries and
adrenal glands in women. These hormones are quite important
in both sexes, but occur in different concentrations, being
much more predominant in males than in females. This, in
part, is responsible for the typical differences between
the genders.
It is the exposure of the hair follicles to DHT, in a genetically
susceptible person, over a period of time, which leads to
androgenetic alopecia, or male and female pattern baldness.
How does this exposure to DHT occur?
In certain cells of the hair follicle, and in the sebaceous
glands, there are high levels of an enzyme called 5-alpha-reductase.
What this enzyme does is to convert testosterone, which
is delivered to these areas by the blood, into DHT. This
is important not only in understanding the mechanisms of
balding, but also one medical treatment now available: Propecia
(finasteride). What Propecia does is inhibit, or limit the
activity of, this 5-alpha-reductase enzyme. Therefore, there
is less conversion of testosterone to DHT, and lower levels
of DHT are found in the follicle. In later sections, we
will discuss this and other medical treatments in much greater
detail.
Aging
There is no set age at which balding occurs. It is a process,
and this is a simple, but oft-ignored fact. Like any process,
it can be rapid or slow, it can begin toward the end of
life or in the late teens, and it can progress in a predictably
inexorable fashion, or it can stop and start, seemingly
stabilize, and then begin again. Once we understand and
accept this as a dynamic process, then we can better plan
for the present and for the future in terms of how we treat
it. This quest for understanding, which you have begun just
by opening this book, will do more than all the despairing
thoughts, hand-wringing, and self-pity, toward allowing
a clear-eyed, rational, long term approach to the problem
of hair loss.
So we now have looked at these three interdependent factors
that play into the common types of balding. Again, they
are: hormones, genetics, and Father Time. So what exactly
does happen to the hair? Let’s take a look.
Assuming we have a genetically predisposed person, then
as the follicles are continuously exposed to DHT, an interesting
phenomenon occurs. Remember the anagen phase, or active
growth phase of the hair? This phase becomes gradually briefer
and briefer, and eventually the hair becomes finer and shorter,
and less deeply colored. We call this "miniaturization"
of hairs. This is also the point at which hair loss tends
to first be noticed. It’s not that there are fewer
hairs on the head, but that their caliber (cross-sectional
area), color and length are so diminished that they no longer
provide "coverage" for the scalp beneath. Light
penetrates through to the shiny scalp, and this is perceived
by the observer as "thinning" or balding.
Also, the ratio between hairs in the anagen phase and those
in the telogen, or resting phase, is increased. This simply
means that, at any given time, an increased number of hairs
are in the telogen phase. These extra numbers of telogen
hairs will be found in the susceptible zone for common balding,
which is the front, top, and crown of the head. The so-called
"permanent" zone, the familiar horseshoe-shaped
wreath of hair around the back and sides, is unaffected
by these changes. The telogen hairs are easily dislodged
during washing, drying, or combing, and this is the second
sign of balding: in addition to the apparent thinning seen
with miniaturization, we begin to see larger numbers of
hairs on the comb, the towel, the pillowcase, or in the
bathroom drain. This can be quite traumatic, especially
for the younger man or for women. In the next section, we
will discuss the natural history of balding, that is, the
way it first presents or appears, the different ways it
progresses, and how it affects the different regions of
the head.
For the sake of completeness, let’s briefly mention
some of the other patterns of hair loss, if only to distinguish
them from androgenetic alopecia (male and female pattern
baldness). There is alopecia areata, where discrete patches
of scalp go bald; triangular alopecia, which tend to occur
in a triangular pattern in the temporal area; alopecia universalis,
in which the entire body may be affected; and various "toxic"
alopecias, including those following a severe illness, sometimes
with high fever, or following pregnancy. Toxic alopecias
may also occur with low thyroid and/or pituitary gland function,
or following chemotherapy. The cicatricial (scarring) alopecias
occur following tissue destruction and inflammation.
Also seen are the so-called diffuse alopecias (patterned
and unpatterned), in which there is widespread thinning
that may affect the "permanent" zone as well as
the areas vulnerable to balding. In any or all of these
less common types of balding above, it may be necessary
to have a complete physical and laboratory workup, possibly
including scalp biopsy.
So again, the common types of balding are directly related
to the presence of male hormones in a genetically predisposed
person over time. This can occur in both men and women.
The process involves progressive miniaturization of the
terminal hairs, and diminished length of the active hair
growth cycle. Now, let’s take a look at how this microscopic,
cellular process is manifested on the head; we can call
this the natural history of balding.
