Page 213 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 7-2 Hair and Nail Diseases

HAMILTON-NORWOOD SCALE FOR MALE PATTERN BALDNESS

ANDROGENIC ALOPECIA

Androgenic alopecia, also known as male pattern bald- 1 4 Mild
ness or female pattern hair loss, is a major form of hair
loss. The age at onset is variable and likely has a genetic
determination. Some men lose their entire scalp hair,
resulting in baldness. Baldness is rare in women,
because their hair loss manifests as varying grades of
thinning.
Clinical Findings: There are variable degrees of male Moderate
pattern hair loss. The Hamilton-Norwood scale has
been used to grade the degree of hair loss. Grade I 2 4A
is manifested by receding frontal hair. Grade VII is
near-total loss of the scalp hair with some sparing of
the inferior occiput. The age at onset of androgenic
alopecia in men can be any time from puberty into Severe
adulthood. Most men older than 50 years of age exhibit
some form of androgenic hair loss. The Caucasian
population is much more prone to developing andro-
genic alopecia than the African American or Asian
population.
Female pattern hair loss can be more difficult to treat 2A 5
because of the importance society places on appearance
and the psychological effects that hair loss can have on
women. Most women do not go bald, but some develop
severe thinning of the vertex. A characteristic finding
in androgenic female pattern hair loss is preservation of
the frontal hair line. This form of hair loss is seen more
commonly in the postmenopausal population.
Histology: Evaluation of a 4-mm punch biopsy speci-
men by the horizontal method is the best technique to
evaluate hair loss. In androgenic alopecia, the follicles 3 5A
are normal in number, but they show evidence of min-
iaturization. Vellus hairs are increased in number.
Whereas the normal scalp has been shown to have a
vellus-to-telogen hair ratio of 1 : 7, the ratio in andro-
genic alopecia is 1 : 3.5. The hair shaft diameters of the
terminal hairs are inconstant, which corresponds to the
miniaturization affect.
Pathogenesis: Androgenic alopecia has been shown
to follow an autosomal dominant pattern of inheritance. 3A 6
It is believed to result from an abnormal response of
the hair follicle to androgens (i.e., dihydrotestosterone).
This androgen has been shown to cause miniaturization
of the terminal hairs over successive hair cycles. As
the hair follicles miniaturize, they become smaller with
a thinner caliber. This causes less scalp coverage, which
manifests as hair thinning. The actual hair follicles
are not scarred or lost. Inhibition of the production of
dihydrotestosterone from its precursor, testosterone, is
one therapeutic tactic. 3V 7
Treatment: Therapy for male pattern baldness
includes use of the topical agent minoxidil 5%, applied
twice daily, with or without the oral 5α-reductase
inhibitor, finasteride. 5α-Reductase is the enzyme
responsible for converting free testosterone into dihy-
drotestosterone. Both these agents have been shown in
multiple randomized studies to decrease the rate of hair
loss and increase the hair shaft diameter. These medica-
tions are well tolerated and have minimal side effects. to treat early in the course of disease to maximize the hair pattern. This is best accomplished with minigrafts
Patients with prostate cancer should avoid the use of effects of the medication. Topical minoxidil may cause of 1 to 2 follicles at a time. A strip of the patient’s
finasteride unless approved by their oncologist. The excessive hair growth on the forehead and temples if it hair is removed from the occipital scalp, and each indi-
only option at present for women with androgenic alo- is applied in these regions. This can be disconcerting vidual hair is dissected out. The separated hair follicles
pecia is topical minoxidil 2%. This has been shown to for patients, and they need to be educated on the proper are then tediously inserted into the desired areas.
decrease the rate of hair loss. application of the medication. Patients can have an excellent result, and the trans-
Most patients who use minoxidil experience a slowing Hair transplantation techniques continue to improve. planted hair appear to be resistant to the effects of
of hair loss, and some see increased growth. It is critical The goal of surgery is to leave a natural-appearing dihydrotestosterone.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 199