What causes male
pattern baldness?
The causes of male pattern baldness are thought to be complex
and are not completely understood. However, as suggested by its medical name (androgenetic
alopecia), male pattern baldness seems to involve both hormonal (androgen) and genetic
factors. Many different types of hormones play roles in the regulation of scalp hair, but
the hormones with the largest effect are the androgens. Testosterone and its more potent
derivative dihydrotestosterone (DHT) are responsible for increasing the size of hair
follicles in areas such as the beard and underarm during puberty, but can also cause hair
follicles in the scalp to decrease in size later in life. These contrasting responses to
DHT might be explained by genetic differences in the individual hair follicles. Similarly,
in men who are balding, genetically determined characteristics of hair follicles in the
scalp may cause the follicles to be more likely to degrade in the presence of androgens.
Hair follicles become miniaturized, and the hair consequently becomes thinner and shorter.
The growing phase of the growth cycle becomes progressively shorter, which means more
hairs are shed. Although the follicles still have an adequate blood supply, they continue
to shrink, and some eventually die.
Whatever the exact causes of male pattern baldness may be, it
is a hereditary trait. There are multiple genetic factors that influence male pattern
baldness. A tendency toward baldness in the men on either the mother’s or
father’s side of a man’s family indicates a genetic predisposition to baldness.
The speed, pattern, time of onset, and degree of balding are all influenced by heredity.
Generally, the earlier the onset of balding, the more extensive the degree of hair loss
will eventually be.
Contrary to popular myth, balding is not caused by wearing
hats. Massaging or brushing the scalp will not help regrow hair, and excessive cleaning of
the scalp will not “unclog” follicles and allow hair growth. While extreme
psychological stress may contribute to a form of hair loss known as alopecia areata,
normal everyday stress does not contribute to balding and is not a cause of androgenetic
alopecia.
www.niddk.nih.gov
