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Is
androgenetic alopecia a disease or part of the natural aging process?
A very difficult question to answer. There are dermatologists
who regard androgenetic alopecia as a disease and there are those
who believe it is simply part of the aging process. There are two
slightly different dictionary interpretations of the word disease.
1) A disease may be a dis-ease, something that causes discomfort,
trouble, inconvenience, or is dangerous to the individual. Androgenetic
alopecia is not painful and does not limit the individual’s
physical ability to live their life as might other life threatening
and life limiting diseases. Androgenetic alopecia may cause emotional
discomfort but this is of our own making in our image oriented society.
In my opinion androgenetic alopecia does not fall within this first
interpretation of disease. 2) The second explanation for the word
disease is a particular destructive process in an organ or organism,
with a specific cause and characteristic symptoms. Clearly, this
interpretation fits with all that we know about androgenetic alopecia.
Hair loss is a gradual destructive process affecting the hair follicles.
Long term androgenetic alopecia will lead to total and irreversible
hair follicle destruction. So, my personal view is that androgenetic
alopecia is a disease albeit not a life threatening one. The fact
that it is so common in the middle aged and elderly does not automatically
indicate that androgenetic alopecia is part of the natural aging
process. Indeed, androgenetic alopecia need not develop in an individual
even if they are genetically extremely predisposed towards development
(see “How can we really be sure that androgenetic alopecia
is caused by androgen hormones?” below).
What
is the evolutionary significance of androgenetic alopecia?
There are two possible options that are regularly discussed. 1)
The human body was not designed for survival beyond thirty years
of age or so. Our intellectual development has given us the power
to prolong our own lives through medicine and sanitation. Androgenetic
alopecia truly expresses its self in middle and old age, well beyond
the age of death our evolutionary ancestors had to contend with.
So it may be that androgenetic alopecia has no real evolutionary
significance.
2) Our primate ancestors may have had the ability to develop androgenetic
alopecia but only a very few of the most senior individuals may
have actually had hair loss. Androgenetic alopecia may have been
utilized as an indicator of the physical and cultural status of
the individual. For example, grey hair on the backs of male mountain
gorillas is a signal of superiority in a community. Alopecia may
have been a similar signal for our ancestors. Stump tailed macaques
and certain species of chimpanzee develop androgenetic alopecia.
Stump tailed macaque alopecia is pathologically very similar to
human androgenetic alopecia. Their alopecia affects both males and
females in similar numbers and develops as a gradual hair loss from
the front. Males typically have more severe alopecia than females.
The hair loss is androgen dependant and stump tailed macaques have
been used as an research model for androgen dependant diseases.
Research has shown that juvenile stump tailed macaques have increased
concentrations of dihydrotestosterone in the frontal scalp regions
as a result of high levels of 5 alpha reductase that converts testosterone
to dihydrotestosterone.
Is
androgenetic alopecia becoming more common?
It is practically impossible to answer this question. Very few
in depth statistical evaluations have been conducted in the past
or present to determine the true frequency of androgenetic alopecia
in the general population. We have no firm evidence that androgenetic
alopecia globally is on the increase. There has been a suggestion
from Japanese researchers that androgenetic alopecia has increased
in prevalence in Japan since the Second World War. This has been
attributed to a “westernization” of the Japanese diet
and increased meat intake although there is no conclusive proof
for this statement. However, we do know there is a strong biochemical
link between cholesterol concentrations in our bodies and androgen
production. It may be possible that increased meat (saturated
fat) intake promotes increased cholesterol levels and this ultimately
affects androgen production.
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