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How
can we really be sure that androgenetic alopecia is caused by androgen
hormones
Very simple, and it is based on an observation first made by ancient
Greek doctors. If you want to find out the effects of some naturally
produced chemical in the body then you stop its production and see
what happens. The easiest way to stop production is to locate the
organ making the product and surgically remove it. The main production
source of androgen hormones in men is the testes. So, to find out
if androgens are important in androgenetic alopecia we must look
at hair patterns in castrated men.
Stopping production of hormones and other chemicals may have a
big impact on the individual so medical experiments of this type
are not intentionally carried out in modern day research. However,
such experiments have been unconsciously instigated by different
populations around the world as part of local culture requirements.
An experiment in castration was carried out when past culture dictated
some boys should be castrated to ensure their voice did not “break”
and indeed to provide eunuch servants. Not so long ago in the western
world surgical castration was routinely conducted on mentally retarded
individuals. Fortunately this is not common practice today. Currently,
castration is conducted primarily to treat men with prostate carcinoma
that is resistant to drug therapy. Whether the reasons for castration
are/were right or wrong, observations on such individuals can tell
us a lot about the effects of androgens in pattern baldness.
After onset of puberty in non castrated men androgenetic alopecia
may develop as normal. Castration post puberty has been noted to
stop further progression of any androgenetic alopecia that may have
developed. Post pubertal castration does not permit much hair regrowth,
rather it stabilizes the hair loss. It was noted by ancient Greek
doctors that boys castrated pre puberty never developed androgenetic
alopecia even if their parents and other family members did and
this observation was confirmed with several studies in the 1940s-50s.
It would seem that hair follicles must be exposed to androgenic
hormones during puberty to potentiate them, make them susceptible
to being affected by androgenetic alopecia later in life. Stopping
hair follicles from "seeing" androgens prohibits any chance
of androgenetic alopecia development.
Relating this knowledge to androgenetic alopecia in women is more
difficult. Women do not have testes (!) But can have hair loss due
to androgens. For women the source of androgens comes from the combined
activity of the ovaries and the adrenal glands. Ovariectomy (Surgical
removal of the ovaries) has been noted to have limited effect on
female androgenetic alopecia. Adrenal gland removal is a very serious
undertaking and potentially life threatening so we do not have much
data on whether pre pubertal blocking adrenal androgens would prohibit
onset of female androgenetic alopecia later in life. However, comparing
the pathology and biochemistry of male and female androgenetic alopecia
indicates the mechanism of disease is essentially the same.
How
can we really be sure that androgenetic alopecia is caused by androgen
hormones references
- Hamilton
JB. Age, sex and genetic factors in the regulation of hair growth
in man: a comparison of Caucasian and Japanese populations. In:
The biology of hair growth. Montagna W, Ellis RA (eds), 1958,
Academic Press, New York, 399-433.
- Hamilton
JB. Effect of castration in adolescent and young adult males upon
further changes in the proportion of bare and hairy scalp. J Clin
Endocrinol metab 1960; 20:1309-1315.
- Hamilton JB. Male hormone stimulation is
a prerequisite and an incitement in common baldness. Am J Anat
1942; 71:451-80
- Hamilton JB. The role of testicular secretions
as inicated by the effect of castration in man and by studies
of pathological conditions and the short life-span associated
with maleness. Rec Prog Hormon Res 1948; 3:257-322.
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