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I
have started using finasteride to treat my pattern baldness. I seem
to have a very oily scalp and hair. Why
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section of a human hair
follicle canal with a sebaceous gland attached
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Scalp sebaceous glands attached to hair follicles are regulated
by a complex system involving androgens. They are particularly stimulated
by testosterone and dihydrotestosterone (DHT) into increased oil
production. For example, in one study looking at oil producing sebaceous
gland activity in acne, a dose of 2% testosterone cream was applied
to the forehead of eight boys for 6 weeks and the effect determined
by measurements of sebum excretion rate (SER). Three boys showed
a 15-fold increase in SER, three were non-responders,and two boys
had SER values between those of the responders and non-responders.
The sebaceous gland is sensitive to testosterone and need not be
stimulated be DHT. For example, men with a genetic deficiency in
5 alpha reductase, the enzyme that converts testosterone to DHT,
still have normally functioning sebaceous glands despite having
no DHT.
In addition, androgens other than testosterone and DHT may affect
sebaceous gland acitivity. Several studies have suggested that adrenal
gland derived dehydroepiandrosterone sulfate (DHEAS) can have a
significant affect on sebaceous gland activity and that DHEAS levels
are directly associated with sebaceous gland activity levels. These
and other data show that sebaceous glands are stimulated by androgens
to varying degrees in different people.
Propecia is only a 5 alpha reductase type II inhibitor. Type I
remains fully active and it is type I that is the primary iso-enzyme
active in acne and sebaceous gland oil secretions. So while there
may be a systemic reduction of testosterone to DHT conversion through
type II reductase inhibition, there is still a significant level
of type I 5 alpha reductase activity in the hair follicle. Further,
the lipid rich sebaceous gland cells are preferred areas for type
I 5 alpha reductase activity. It may be that while overall reductions
in DHT promote hair fiber formation in the hair follicle bulb region,
the continued local DHT production and the presence of testosterone
in the sebaceous gland is enough to stimulate sebum secretion.
Finally, propecia blocks conversion of testosterone to DHT. so
with reduced conversion, the net amount of testosterone in the blood
increases. As sebaceous glands are sensitive to testosterone levels
as well as DHT, sometimes there is an increase in oil/sebum production
when using propecia.
I
have started using finasteride to treat my pattern baldness. I seem
to have a very oily scalp and hair. Why references
- Holland DB, Cunliffe WJ, Norris JF. Differential
response of sebaceous glands to exogenous testosterone. Br J Dermatol.
1998 Jul;139(1):102-3.
- Ebling
FJ. Hair follicles and associated glands as androgen targets.
Clin Endocrinol Metab. 1986 May;15(2):319-39.
- Stewart
ME, Downing DT, Cook JS, Hansen JR, Strauss JS. Sebaceous gland
activity and serum dehydroepiandrosterone sulfate levels in boys
and girls. Arch Dermatol. 1992 Oct;128(10):1345-8.
- Imperato-McGinley
J, Gautier T, Cai LQ, Yee B, Epstein J, Pochi P. The androgen
control of sebum production. Studies of subjects with dihydrotestosterone
deficiency and complete androgen insensitivity. J Clin Endocrinol
Metab. 1993 Feb;76(2):524-8.
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