Androgenetic alopecia (male-pattern
baldness)
Although
clearly familial, the exact mode of inherit-ance has not yet been clarified.
The idea of a single autosomal dominant gene, with reduced penetrance in women,
now seems less likely than a polygenic type of inheritance. Male-pattern
baldness is androgen-dependent; in females, androgenetic alopecia, with
circulating levels of androgen within normal limits, is seen only in those who
are strongly predisposed genetically.
The common pattern in men (Fig. 13.9) is the loss of hair first from the temples, and then from the crown.
However,
in women the hair loss may be much more diffuse (Fig. 13.10), particularly over
the crown. In bald areas, terminal hairs are replaced by finer vellus ones.
Hair
loss is relentless, tending to follow the family pattern with some losing hair
quickly and others more slowly. The diffuse pattern seen in women tends to
progress slowly.
Even minor hair loss may lead to great anxiety and rarely to a monosymptomatic hypochondriasis. Bald scalps burn easily in the sun, and may develop multiple actinic keratoses. It has been suggested recently that bald men are more likely to have a heart attack than those with a full head of hair.
The
diagnosis is usually obvious in men, but other causes of diffuse hair loss have
to be considered in women.
None
are usually needed. In women virilization may have to be excluded.
Scalp
surgery, hair transplants and wigs are welcomed by some. Topical application of
minoxidil lotion may slow early hair loss and even stimulate new growth of hair
in a few cases. Small and recently acquired patches respond best. When
minoxidil treatment stops, the new hairs fall out after about 3 months.
Anti-androgens help some women with the diffuse type of androgenetic alopecia.
Finasteride
(Propecia), an inhibitor of human type
II 5α-reductase,
reduces serum and scalp skin levels of dihydrotestosterone in balding men. At
the dosage of 1 mg /day, it may increase hair counts and so lead to a
noticeable improvement in scalp hair. However, the beneficial effects slowly
reverse once treatment has stopped. This treatment is not indicated in women or
children. Side-effects are rare, but include decreased libido, erectile
dysfunction and altered prostate-specific antigen levels.
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