term androgenetic can be broken down into two terms: Andro and Genetic. "Andro" refers
to the androgens (testosterone, dihydrotestosterone)
which are necessary to produce male-pattern
hair loss (MPHL); while "Genetic" refers
to inherited genes which are crucial factors
for this type of baldness.
Androgens, dihydrotestosterone in particular,
play important roles in the development of
this pattern of hair loss. Genetic factor
could modify the extent to which the hair
follicles respond to circulating androgens
as well, and this genetically determined disorder
takes effect through the gradual conversion
of terminal hairs, first into indeterminate
hairs, and finally to vellus hairs. Research
concluded that the size of the dermal papilla
ultimately dictates the size of the growing
hair, and in AGA, some dermal papilla cells
were lost either by apoptosis, or by cell
Three Key Features of Androgenetic Alopecia
Pathogenesis in men
1. Alteration of hair cycle dynamics
Men with pattern baldness have a reduction
in the terminal-to-vellus hair ratio and
exhibit a typical distribution of hair
2. Follicular miniaturization
Hair follicles contain androgen receptors.
Genes that shorten the anagen phase become
active and hair follicles shrink. With
successive anagen cycles, the follicles
This leads to shorter and finer hair and
the non-pigmented vellus hairs replace
pigmented terminal hairs. All the hairs
on the affected
area may be involved in the shrinking
process and the region may be covered
hardly visible vellus hairs after sometime.
Along with hair miniaturization, the production
of pigment also ceases.
Androgens and Hair Growth
Androgens serve as mediators for terminal
hair growth in every part the body and create
profound effects on human scalp and body hair.
Scalp hair may grow even in the absence of
androgens, while body hair growth depends
on androgens’ performance. With androgens’ activity,
those genetically predisposed develop scalp
alopecia, manifested as miniaturization or
shrinking of scalp hair follicles in a defined
pattern. Androgens cause enlargement of vellus
hairs to form terminal follicles in the axilla
and pubis in both sexes, on the face, chest
and men’s extremities. The seemingly
paradoxical effects of androgens on scalp
and body hair are still a grey area. Studies
about this matter provide greater understanding
on molecular mechanisms by which androgens
regulate hair growth.
It is very much easy to recognize the clinical
appearance of pattern baldness in most
men. The transition from large thick-pigmented
terminal hairs to thinner, shorter, indeterminate
hairs and finally to non-pigmented vellus
hairs in the involved areas take place gradually.
Therefore, increase in hair shedding would
be noticeable. Androgenetic alopecia takes
place in men by gradual thinning in the temporal
areas, followed by progressive thinning in
the frontal and vertex areas of the scalp.
Recession of the frontal hairline is common
and frontal and vertex thinning areas may
merge, and all the hair all over the crown
For men with pattern baldness, it is
rare to undergo histological diagnosis. However,
when the diagnosis on some patients is ambiguous,
4mm punch biopsies are ideally taken from
the vertex of the scalp. Two biopsies should
be taken - the horizontal and the vertical
Terminal anagen hairs are replaced by secondary
psuedo-vellus hairs with residual angiofibrotic
tracts called follicular streamers or stellae.
Vertical sectioned scalp biopsies show a marked
reduction in these hairs which normally penetrate
through the dermis into the subcutis. Apparently,
there is a reduction in the number of follicles.
Horizontal sectioning yields more information
on the number and types of follicles which
could assist in a more accurate diagnosis.
On horizontal sections of scalp biopsies,
many pseudo-vellus hair follicles can be identified
in the papillary dermis. These indicate that
follicles are shrinked rather than destroyed.
Pseudo vellus hairs are distinguished from
true vellus hairs by the presence of the arrector
pili muscle and angiofibrotic streamers.
Others features that may be seen include
follicular fibrosis (formation of excess fibrous
tissue) which can be seen in around 10% cases,
and perifollicular inflammation. These features
are non-specific as they maybe commonly seen
in some normal scalp.
Normally, treating any kind of hair loss
comes in steps - reversal of the hair loss,
stabilization of the process, and prevention
of the condition. So far, none of the currently
available treatments has been proved to be
successful in treating pattern baldness.
However, there is no life risk in pattern baldness in men that is why it is best to
take no treatment at all and allow the balding
to progress naturally.
Medical Treatment: The only two treatments
that are currently approved by the US Food
and Drug Administration for the management
of pattern baldness are topical minoxidil
and oral finasteride.
Scalp Surgery: This can involve transplants,
scalp reduction, rotation flaps, punch grafting,
and single follicle transplantation.
Non medical treatment: If patients with
mild alopecia do not wish to have medical
they can disguise their baldness by using
spray-on scalp dye treatments. These could
create an appearance of thicker hair.
Patients with advanced alopecia could
baldness by wearing quality wigs that
appear like natural
Cases of pattern baldness are increasing
among men, and many find this condition frustrating.
Stem cell scientists, geneticists, developmental
biologists and immunologists are continuously
working on the progress of hair biology to
find effective treatments for the disease.