Hair Loss Causes and Conditions
P. Cole, MD
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 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.
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.
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"
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
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