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The reader would probably agree that the fol-
lowing are generally recognized as safe to
claim with regard to androgenic alopecia
(AGA) and contribute to androgenic theory:
• 5-alpha reductase enzyme activity, which con-
verts testosterone to dihydrotestosterone (DHT),
increases in balding scalp,1
• DHT increases in balding scalp,2,3
• Number of DHT receptors on the hair follicles
increases in balding scalp,4
• Blocking conversion of testosterone to DHT
delays progression of AGA.5
Based on these findings, DHT is held responsible
for miniaturization of hair follicles in AGA.6 How-
ever, as DHT is a more potent form of testosterone
and androgens are expected to convert hair follicles
from vellus to terminal not the other way around,
this inference gives rise to a paradox. In a review
article, Randall says, “How one type of circulating
hormone has such contrary effects on a single tissue
depending on its body site is not clear; this biologi-
cal paradox alone makes androgen action in hair fol-
licles very intriguing.”7 It is indeed so.
Androgen-dependent/independent and andro-
gen-sensitive/insensitive hair follicle concepts have
been used to explain the opposite effects of andro-
gens on hair follicles at different body sites.6–8 Ac-
cording to these concepts, nonbalding scalp hair is
designated as androgen independent and androgen
insensitive, whereas balding scalp hair as androgen
independent but androgen sensitive.8 Here, there
is a point that deserves attention. Androgen-de-
pendent/independent hair follicle concept treats
the whole scalp as a single body site, which stands
to reason. Scalp hair, either balding or nonbalding,
is considered androgen independent because they
grow in the absence of androgens as opposed to, for
example, axillary or pubic hair. However, androgen-
sensitive/insensitive hair follicle concept divides the
scalp into 2 sites as androgen-sensitive and andro-
gen-insensitive hair-bearing areas. This arbitrary di-
vision of scalp is discomforting in the first place and
inappropriateness of the concept becomes evident
as it is questioned further.
As stated above, DHT is accepted to be the an-
drogen that binds to androgen receptors and effects
follicular miniaturization. Along with other findings,
this conclusion is based on the finding of increased
levels of DHT in balding scalp compared with non-
balding scalp. Unless DHT levels in balding scalp
are equal to DHT levels in nonbalding scalp, follicu-
lar miniaturization in AGA cannot be considered a
Received for publication July 13, 2013; accepted September 6,
2013.
Copyright © 2013 The Authors. Published by Lippincott
Williams & Wilkins on behalf of The American Society of
Plastic Surgeons. PRS Global Open is a publication of the
American Society of Plastic Surgeons. This is an open-access
article distributed under the terms of the Creative Commons
Attribution-NonCommercial-NoDerivatives 3.0 License,
where it is permissible to download and share the work
provided it is properly cited. The work cannot be changed in
any way or used commercially.
DOI: 10.1097/GOX.0000000000000005
From Ankara, Turkey.
Summary: What is wrong with the current understanding of etiopatho-
genesis of androgenic alopecia (AGA)? What is the most important question
to ask to understand AGA? Why is that question skimped? Which findings
are interpreted incorrectly? Is there anything that has not been discerned
about AGA until today? What are the deceptive factors for investigators?
Is it possible to snap the whole view uninterruptedly in one clear picture?
Answers and an overview with fresh perspectives are provided. (Plast Reconstr
Surg Glob Open 2013;1:e64; doi: 10.1097/GOX.0000000000000005; Published
online 28 October 2013.)
Emin Tuncay Ustuner, MD
Cause of Androgenic Alopecia: Crux of
the Matter
Disclosure: The author holds a patent on prevention
and treatment of male pattern baldness (U.S. Patent
No.7914548). The Article Processing Charge was paid
for by the author.
Cause of Androgenic Alopecia
Ustuner
xxx
xxx
XXX
Mythili
Plastic & Reconstructive Surgery-Global Open
2013
XXX
Special Topic
10.1097/GOX.0000000000000005
6September2013
13July2013
(c) 2013 The Authors. Published by Lippincott Williams & Wilkins on behalf of The Amer-
ican Society of Plastic Surgeons. PRS Global Open is a publication of the American Society
of Plastic Surgeons.
SPECIAL TOPIC
PRS GO • 2013
2
matter of sensitivity to androgens. The amount of
androgen is not the same in the so-called androgen-
insensitive area.
In a relatively recent review article, the role of
androgens in the pathophysiology of AGA is docu-
mented by Kaufman.6 Kaufman says, “In men with
MPHL (male pattern hair loss), follicular miniatur-
ization is caused by an inherited sensitivity of scalp
hair follicles to normal levels of circulating andro-
gens.” “Thus, it appears that in balding men DHT
binds to androgen receptors in susceptible hair folli-
cles and, by an unknown mechanism, activates genes
responsible for follicular miniaturization.”
Kaufman tries to put it right saying sensitivity to
“normal levels of circulating androgens” to no avail.
It helps correct the terminology from one point of
view only and obviously does not bring in an expla-
nation to the opposite effects of androgens on bald-
ing scalp hair follicles vs hair follicles at other body
sites. If there is sensitivity to normal levels of circu-
lating androgens and the resulting product of this
sensitivity is DHT, an overall pronounced effect is
expected not an opposite effect. DHT is a stronger
form of testosterone.
Androgen sensitivity concept is not only an inept
concept to explain the role of androgens in AGA
but it is also confusing and misleading its adopters
after some dubious “genes responsible for follicular
miniaturization” and “an unknown mechanism” that
activates them. Worst of all, it skimps the most criti-
cal question and prevents it from standing forward,
which is:
• Why does DHT (or 5-alpha reductase enzyme ac-
tivity) increase in balding scalp?
This question requires a solid answer and has pri-
ority over the other crucial questions that are as fol-
lows:
• How does DHT cause hair loss while exactly the
opposite effect is expected?
• Why does balding (or increase in DHT levels) oc-
cur only at the top of the head?
If these questions are considered fair questions, a
valid theory on the etiology of AGA has to be able to
answer all of these questions.
I introduced a new theory in 2008.9 It does ac-
complish this hard task adroitly; moreover, it is in
agreement with all findings in connection with AGA.
The mechanism of AGA is thought to be highly com-
plex.10 However, this theory provides a new viewpoint
from which it seems to be quite simple. According to
the theory, pressure on the hair follicles created by
the weight of the scalp is the cause of AGA. Total
weight of the skin, subcutaneous connective tissue,
and galea are operative. With sandwiched fat tis-
sue and fibrous connections between the skin and
galea, all of these components of the scalp form a
combined structure that sits on the cranial bones
much like a separate structure movable on the cra-
nial bones due to the intervening loose areolar tis-
sue. Hair follicles are compressed by the skin against
the calvarial bones. This theory is uniquely capable
of explaining all related phenomena and paradoxes.
In summary, the theory points out that the pres-
sure on the hair follicles is buffered by the surround-
ing subcutaneous fat tissue and young dermis that is
capable of keeping itself well hydrated. As one ages,
thickness of the subcutaneous fat tissue and the vol-
ume of the dermis decreases,11,12 that is, the buffer
decreases and consequently the pressure on the hair
follicles increases. Another factor that is well known
to cause thinning of subcutaneous fat tissue much
more rapidly than aging is testosterone.13–16 With
the onset of puberty, subcutaneous fat tissue starts
to decrease instantaneously at an early age in the
male due to increase in testosterone levels.17,18 Estro-
gen protects the cushioning tissues until after meno-
pause in the female.19–24 And, testosterone effected
reduction in subcutaneous fat tissue normally does
not happen in the female at all.
On the other hand, it has been shown that the
downward growth of early anagen follicle occurs by
growth pressure.25,26 It has to work against the com-
pressive force described above. As the cushion reduc-
es, the hair follicle needs to strive against a higher
pressure to reach its terminal follicle size. More an-
drogen is demanded to promote the growth. This is a
local demand, and there is a mechanism for increas-
ing the effect of androgens locally without raising
systemic androgen levels. 5-alpha reductase enzyme
activity increases at the locale and converts more tes-
tosterone to DHT, which has severalfold greater af-
finity for androgen receptors than testosterone. And,
DHT increases locally. The sequence of reactions
Fig. 1. The vicious circle in AGA.
Ustuner • Cause of Androgenic Alopecia
3
does not end here. Increased DHT causes further
erosion of the subcutaneous fat tissue around the
hair follicle.27–29 A vicious circle is created (Fig. 1).
There is not another theory that reasonably
and satisfactorily explains hair loss in AGA without
ascribing a function to DHT that is opposite to its
known function. DHT increases to help the hair fol-
licle forge ahead deeper to reach its normal terminal
follicle size in the face of increased pressure due to
decrease in cushioning tissues. As long as the pres-
sure on the follicle is adequately buffered, a base
androgen level is enough and required for healthy
hair growth.30 As the cushion decreases, the balance
is lost at some point and the vicious circle is initi-
ated. Increased DHT promotes hair growth proba-
bly mainly by stimulating mitosis in the early anagen
follicle. However, increased growth pressure due to
advanced mitosis cannot overcome the compressing
pressure on the hair follicle but speeds up and short-
ens the anagen phase. Hair follicle cannot grow to its
full size and becomes smaller and smaller with each
cycle along with the increasing pressure on the hair
follicle. Hair follicle miniaturization, that is, termi-
nal to vellus conversion, takes place, anagen to telo-
gen ratio reduces, and hair loss increases.
A reaction-dubbed microinflammation around
the bulge region of individual hair follicles in bald-
ing scalp has been presumed a causative factor in
AGA,31,32 but most likely it is evidence for the new
theory. A reaction that is much milder than the in-
flammation seen in a typical inflammatory scarring
alopecia and takes place at the site of mitosis suggests
scavenging of products resulting from inefficient mi-
tosis rather than a factor in the etiology of AGA.
Finally, if the pressure created by the weight of the
scalp causes the hair loss in AGA, which is claimed
by the theory, it is expected that the hair at the top
of the head is lost. This is exactly what happens in
AGA. Although the conformity is manifest and there
is an appreciable relation between the shape of the
cranium and the hair loss area in AGA, a few points
have to be observed so as not to get confused.
It is better to examine only the last-stage AGA cas-
es observing and evaluating the hair loss area from
this theory point of view for the first time. AGA is a
progressive condition, and there are several factors
that can be effective on where hair loss starts and
how it progresses in different individuals. Observing
more hair loss at presumedly lower pressure areas
than higher pressure areas in intermediate-stage
AGA cases can be deceptive and is the most common
source of confusion.
An example of the relation between the shape
of the cranium and the hair loss area is shown in
Figure 2. Outlines of the side views and back views of
2 heads are seen. The only difference between the 2
heads is the shape of the back of the calvarium. One
of them is rather rounded in shape (Fig. 2A), where-
as the other is more like 2 oblique surfaces that meet
at an obtuse angle (Fig. 2C). Hair loss area extends
down to where the back of the upright head contacts
with a vertical line (red line in the drawing). The
pressure is relieved below this contact site as the scalp
turns away from the vertical direction. Most of the
time the point of pressure relief is located at a lower
level in the latter type (Fig. 2D) than in the former
(Fig. 2B), so that looking from behind the person a
bigger bald area is seen in the latter. This finding is a
strong revealing finding for the new theory but may
be misleading if it is not interpreted correctly.
Also, the structure of the scalp has to be given due
consideration during the evaluation of hair loss area
in relation to the shape of the cranium. For example,
even if the back of the head is precisely straight and
vertical when the head is upright, the weight of the
scalp still creates pressure on the hair follicles at the
back of the head although the direction of the gravi-
tational force is vertical, that is, parallel to the back
of the head (the same applies for the hair follicles
within the contact site with the vertical line in the
previous example). Galea aponeurotica is a tough
nonelastic structure and there are dense, nonelastic
fibrous attachments between the galea and the skin
of the scalp. Downward pull in the vertical direction
Fig. 2. The relation between the shape of the cranium and the hair loss area in AGA is a proof
for the validity of the new theory. Hair loss extends to where a vertical line makes contact
with the back of the upright head. Depending on the shape of the back of the head, this
point may be at a higher (A, B) or lower (C, D) location.
PRS GO • 2013
4
on the skin of the back of the head is opposed by
these nonelastic fibrous attachments. The resulting
net force is toward the calvarium and it compresses
the hair follicles (Fig. 3). Therefore, in such cases,
hair loss area is expected to extend down usually to
the level of the border of the galea with the occipita-
lis muscle at the back of the head.
One more important point that should be re-
garded is that the force of downward pull caused by
the gravity on the scalp skin is not distributed equally
around the circumference of the head (Fig. 4). As
the ears are firmly fixed to the temporal bones, they
interrupt the soft-tissue continuity, shore up the soft
tissues above and around them, and assume the pull
of the soft tissues below. By contrast, scalp skin is con-
tinuous with the skin of the face between the ears and
eyes on both sides of the face, so that the weight of
the facial soft tissues adds to the pressure in the fron-
tal part of the scalp. The circumstances are similar
at the back of the head in terms of effective weights.
The weight of the soft tissues below the ear level at
the back of the head similarly adds to the pressure in
the vertex area as an extra weight compared with the
area above the ears. In most of the AGA cases, hair
loss starts at the frontal and/or vertex areas.
The new theory’s unparalleled ability to explain
even the details of the hair loss process and the for-
mation of the pattern in AGA is apparent.
In his review Trüeb10 states that genetic involve-
ment in AGA is pronounced, but no specific gene has
been identified yet and genetic predisposition to AGA
remains poorly understood. He continues, “We prob-
ably deal with a polygenic inheritance, dependent on
a combination of mutations, e.g. in or around the AR
(androgen receptor) gene affecting the expression of
the AR, and other genes controlling androgen levels.”
However, systemic androgen levels are normal in AGA,
DHT increases locally and the enzyme that converts
testosterone to DHT is 5-alpha reductase. In the same
review, Trüeb acknowledges that the genes encod-
ing the two 5-alpha reductase isoenzymes have been
shown not to be associated with AGA by Ellis et al.33
That is, although there are many findings that suggest
genetic involvement in AGA, DHT increase in AGA is
not an occurrence directly determined by genes.
It comes to the same question again: Why does
DHT increase in balding scalp? This is the crux of
the matter.
Fig. 3. Fat tissue and brous bands between the skin and galea of the scalp in a hypotheti-
cal case wherein the back of the calvarium is vertical and straight are depicted. (A), If there
were no gravity, there would not be a downward pull, whereas (B) in the presence of gravity,
downward pull on the skin at the back of the head is directed inward because of the inelastic
brous bands connecting the skin to the inelastic galea and resisting the gravity.
Fig. 4. Anatomy is a determining factor on the magnitude of
the downward pull at dierent parts of the scalp. Middle top
of the scalp is supported by the ears in contrast with the fron-
tal and vertex regions. Soft-tissue loads on the frontal and
vertex areas of the scalp are more than the soft-tissue load
on the middle top.
Ustuner • Cause of Androgenic Alopecia
5
Since its introduction, the new theory has been
regarded with notable skepticism and resistance.
Simplifying a very complicated problem is probably
the only disadvantage of the theory. AGA has been
one of the biggest and most challenging problems
of the humankind. It has affected so many lives
throughout the human history and has been a dev-
astating condition for so many of the afflicted. It is
difficult to settle for any mechanism less than highly
complex. However, all natural phenomena that
seem to be complex look simpler if viewed from the
right standpoint.
Emin Tuncay Ustuner, MD
Ankara 06660, Turkey
E-mail: ustuneret@gmail.com
REFERENCES
1. Sawaya ME, Price VH. Different levels of 5alpha-reductase
type I and II, aromatase, and androgen receptor in hair
follicles of women and men with androgenetic alopecia. J
Invest Dermatol. 1997;109:296–300.
2. Schweikert HU, Wilson JD. Regulation of human hair
growth by steroid hormones. I. Testerone metabolism in
isolated hairs. J Clin Endocrinol Metab. 1974;38:811–819.
3. Dallob AL, Sadick NS, Unger W, et al. The effect of fi-
nasteride, a 5 alpha-reductase inhibitor, on scalp skin
testosterone and dihydrotestosterone concentrations
in patients with male pattern baldness. J Clin Endocrinol
Metab. 1994;79:703–706.
4. Hibberts NA, Howell AE, Randall VA. Balding hair follicle
dermal papilla cells contain higher levels of androgen re-
ceptors than those from non-balding scalp. J Endocrinol.
1998;156:59–65.
5. Kaufman KD, Olsen EA, Whiting D, et al. Finasteride
in the treatment of men with androgenetic alopecia.
Finasteride Male Pattern Hair Loss Study Group. J Am
Acad Dermatol. 1998;39(4, Part 1):578–589.
6. Kaufman KD. Androgens and alopecia. Mol Cell Endocrinol.
2002;198:89–95.
7. Randall VA. Androgens and human hair growth. Clin
Endocrinol (Oxf). 1994;40:439–457.
8. Stenn KS, Paus R. Controls of hair follicle cycling. Physiol
Rev. 2001;81:449–494.
9. Ustuner ET. Baldness may be caused by the weight of the
scalp: gravity as a proposed mechanism for hair loss. Med
Hypotheses 2008;71:505–514.
10. Trüeb RM. Molecular mechanisms of androgenetic alope-
cia. Exp Gerontol. 2002;37:981–990.
11. Levakov A, Vucković N, Dolai M, et al. Age-related skin
changes. Med Pregl. 2012;65:191–195.
12. Caso G, McNurlan MA, Mileva I, et al. Peripheral fat loss
and decline in adipogenesis in older humans. Metabolism
2013;62:337–340.
13. Xu XF, De Pergola G, Björntorp P. Testosterone increases
lipolysis and the number of beta-adrenoceptors in male
rat adipocytes. Endocrinology 1991;128:379–382.
14. Frederiksen L, Højlund K, Hougaard DM, et al.
Testosterone therapy decreases subcutaneous fat and
adiponectin in aging men. Eur J Endocrinol. 2012;166:
469–476.
15. Dieudonne MN, Pecquery R, Leneveu MC, et al. Opposite
effects of androgens and estrogens on adipogenesis in rat
preadipocytes: evidence for sex and site-related specifici-
ties and possible involvement of insulin-like growth factor
1 receptor and peroxisome proliferator-activated recep-
tor gamma2. Endocrinology 2000;141:649–656.
16. Corbould A. Chronic testosterone treatment induces se-
lective insulin resistance in subcutaneous adipocytes of
women. J Endocrinol. 2007;192:585–594.
17. Shen W, Punyanitya M, Silva AM, et al. Sexual dimor-
phism of adipose tissue distribution across the lifespan:
a cross-sectional whole-body magnetic resonance imaging
study. Nutr Metab (Lond). 2009;6:17.
18. Enzi G, Gasparo M, Biondetti PR, et al. Subcutaneous and
visceral fat distribution according to sex, age, and over-
weight, evaluated by computed tomography. Am J Clin
Nutr. 1986;44:739–746.
19. Brincat MP, Baron YM, Galea R. Estrogens and the skin.
Climacteric 2005;8:110–123.
20. Hall G, Phillips TJ. Estrogen and skin: the effects of es-
trogen, menopause, and hormone replacement therapy
on the skin. J Am Acad Dermatol. 2005;53:555–568; quiz
569–572.
21. Raine-Fenning NJ, Brincat MP, Muscat-Baron Y. Skin ag-
ing and menopause: implications for treatment. Am J Clin
Dermatol. 2003;4:371–378.
22. Shu YY, Maibach HI. Estrogen and skin: therapeutic op-
tions. Am J Clin Dermatol. 2011;12:297–311.
23. Archer DF. Postmenopausal skin and estrogen. Gynecol
Endocrinol. 2012;28(Suppl 2):2–6.
24. Van Pelt RE, Gozansky WS, Hickner RC, et al. Acute
modulation of adipose tissue lipolysis by intravenous es-
trogens. Obesity (Silver Spring) 2006;14:2163–2172.
25. Magerl M, Tobin DJ, Müller-Röver S, et al. Patterns of pro-
liferation and apoptosis during murine hair follicle mor-
phogenesis. J Invest Dermatol. 2001;116:947–955.
26. Paus R, Müller-Röver S, Van Der Veen C, et al. A com-
prehensive guide for the recognition and classification
of distinct stages of hair follicle morphogenesis. J Invest
Dermatol. 1999;113:523–532.
27. Gupta V, Bhasin S, Guo W, et al. Effects of dihydrotes-
tosterone on differentiation and proliferation of hu-
man mesenchymal stem cells and preadipocytes. Mol Cell
Endocrinol. 2008;296:32–40.
28. Xu X, De Pergola G, Björntorp P. The effects of andro-
gens on the regulation of lipolysis in adipose precursor
cells. Endocrinology 1990;126:1229–1234.
29. Singh R, Artaza JN, Taylor WE, et al. Androgens stimulate
myogenic differentiation and inhibit adipogenesis in C3H
10T1/2 pluripotent cells through an androgen receptor-
mediated pathway. Endocrinology 2003;144:5081–5088.
30. Glaser RL, Dimitrakakis C, Messenger AG. Improvement
in scalp hair growth in androgen-deficient women treat-
ed with testosterone: a questionnaire study. Br J Dermatol.
2012;166:274–278.
31. Jaworsky C, Kligman AM, Murphy GF. Characterization of
inflammatory infiltrates in male pattern alopecia: impli-
cations for pathogenesis. Br J Dermatol. 1992;127:239–246.
32. Mahé YF, Michelet JF, Billoni N, et al. Androgenetic alope-
cia and microinflammation. Int J Dermatol. 2000;39:576–584.
33. Ellis JA, Stebbing M, Harrap SB. Genetic analysis of male
pattern baldness and the 5alpha-reductase genes. J Invest
Dermatol. 1998;110:849–853.
