|
Androgenetic alopecia is the most common type of hair loss in men, accounting for approximately 95% of hair
loss cases. Also known as “androgenic alopecia” or “male pattern hair loss,” this condition
can cause hair loss as early as a man’s 20s and progresses at different rates in different men. Hair thinning
usually begins along the temples and the crown of the head; left untreated, the hair line continues to receded
and hair loss continues on top of the head. Approximately 20% of men in their 20s are affected, 30% in their
thirties and on up to 80% affected by age 80 years.
Adapted from Norwood OT: Male pattern baldness: classification and incidence. South Med
J 1975; 68:1359-1365
While the precise cause of male pattern baldness is not clearly defined, it has a strong hereditary component
that may be passed down from either or both parents. This hereditary link is further supported by studies showing
consistent epidemiological differences between races, with Chinese and African men showing a much lower incidence
of hair loss than in Caucasian men.
Research into the biology of hair growth has revealed useful information
about the stages of hair growth and the biochemical processes related to hair loss. Each hair or “follicle”
normally goes through several phases during its life cycle, including a growth phase. In individuals affected
by androgenetic alopecia, the hair’s growth phase is shortened due to an unusually high tissue level of
the naturally occurring hormone dihydrotestosterone ( DHT ), produced when testosterone reacts with the enzyme
5alpha-reductase ( 5AR ), the enzyme that breaks down testosterone into DHT. Recent studies have linked elevated
scalp concentrations of 5AR with hair loss, while 5AR deficiency is linked with the absence of hair loss.
Information about these biochemical pathways has been used to develop effective pharmaceutical treatments that
may slow or stop progressive hair loss; in some cases, it may even promote hair regrowth. Finasteride
( Propecia ) and minoxidil ( Rogaine ) are the most widely used
FDA-approved pharmaceutical treatments for androgenetic alopecia.
Androgenetic alopecia also affects up to 40% of women. As with men, onset of this type of hair loss may occur
any time from a woman’s early 20s, and over half of women experience some hair thinning by middle age.
However, the pattern of hair loss in women differs from that in men, appearing as generalized hair thinning
rather than localized patches of hair loss. Minoxidil ( Rogaine ) is
the main treatment for androgenetic alopecia in women. More information on
this condition in women.
Androgenetic Alopecia ( eMedicine )
Male Pattern Baldness
( American Medical Association )
Guidelines of Care for Androgenetic Alopecia
( American Academy of Dermatologists )
Practical Management of Hair Loss: Androgenetic Alopecia
( DermWeb )
Androgenetic Alopecia: Pathogenesis and Potential for
Therapy ( EERM )
Androgenetic Alopecia in Men and Women: An Overview
of Cause and Treatment ( Regrowth LLC )
|
