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 follicles Genetics
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 HormonesAll 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.
AgingThere 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.
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