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Why
is there no loss of beard hair when using anti 5 alpha reductase,
or anti androgen drugs
Hair follicles on different parts of the body have different responses
to androgens. Scalp hair follicles miniaturise and become less active
under androgen influence, especially dihydrotestosterone. In contrast,
hair follicles in the pubic areas, and the beard in men, become
larger and more active producing thick coarse hair under the influence
of the exact same hormones. This might seem to suggest that antiandrogen
drugs or any drug that reduces androgen levels near hair follicles,
such as 5 alpha reductase inhibitors, may allow increased hair growth
on the scalp but hair loss in the pubic and beard areas.
This does not happen - or does it? Comments made in conversation
by scientists from Merck, the makers of Propecia, hinted that there
may be some slight slow down in the rate of beard growth when using
Propecia. Merck scientists claimed that individual dermatologists
and some patients using Propecia had contacted the company with
claims that they had reduced beard growth. However, none indicated
actual beard hair loss.
The lack of complete beard and pubic hair loss is probably due
to an apparent "point of no return" that hair follicles
seem to pass through when we reach puberty. It seems that the first
increase in hormones at puberty have a profound effect on determining
the fate of hair follicles in adult life. Once hair follicles in
the beard and pubic regions are switched into coarse hair production
at puberty there is no going back. Equally, once scalp hair follicles
are exposed to androgens in puberty their fate is sealed and the
follicles are susceptible to male pattern baldness.
This is clearly demonstrated by some simple observations made when
androgens were first identified as being important in pattern baldness.
When men are castrated before puberty they never develop pattern
baldness, even when there is a history of baldness in their families
and even if they are given androgen hormone injections when they
are adults. Equally these men have very little or no beard growth.
Their public hair is usually in a female pattern and very sparse
and there is no obvious increase in body hair growth after giving
androgen injections.
In contrast, men castrated during or after puberty do not spontaneously
develop pattern baldness, but if they are given androgen hormone
injections pattern alopecia develops. They also have little beard
growth but beards do develop if the men are given androgen injections.
Clearly the first exposure of hair follicles to androgens during
puberty ensures a permanent switch occurs in androgen receptive
hair follicles. Beard and pubic hair follicles are fated to grow
thick coarse hair. Scalp hair follicles are made susceptible to
androgenetic alopecia. Drastic changes in androgen levels in adult
life may have minor effects on these hair follicles, but beard and
pubic hair follicles cannot be completely switched off by reducing
androgen hormone levels using drugs or otherwise.
Why
is there no loss of beard hair when using anti 5 alpha reductase,
or anti androgen drugs references
- Public
discussion at the 7th European Hair Research Society (EHRS)
Meeting, York UK. 17th-19th September 1999
- Hamilton
JB. Effect of Castration in Adolescent and Young Adult Males
Upon Further Changes in the Proportions of Bare and Hairy Scalp.
J Clin Endocrinol Metab 1960; 20: 1309-14.
- Ebling
FJ. The biology of hair. Dermatol Clin. 1987 Jul;5(3):467-81.
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