Testosterone, prostate cancer, and balding:
Is there a link?
We can thank the Greeks for the name doctors apply to male hormones. Androgen comes
from the words meaning “man-maker,” and it’s a well-chosen
term. Testosterone is the most potent androgen, and it does make the
man. It’s responsible for the deep voice, increased muscle mass,
and strong bones that characterize the gender, and it also stimulates
the production of red blood cells by the bone marrow. In addition,
testosterone has crucial, if incompletely understood, effects on male
behavior. It contributes to aggression, and it’s essential for
the libido or sex drive, as well as for normal erections and sexual
performance. Testosterone stimulates the growth of the genitals at
puberty, and it is one of the factors required for sperm production
throughout adult life. Finally, testosterone also acts on the liver.
Normal amounts are harmless, but high doses can cause liver disease
and boost the production of LDL (“bad”) cholesterol while
lowering the amount of HDL (“good”) cholesterol.
Although testosterone acts directly on many tissues, some of its least
desirable effects do not occur until it is converted into another androgen, dihydrotestosterone (DHT).
DHT acts on the skin, sometimes producing acne, and on the hair follicles,
putting hair on the chest but often taking it off the scalp. Male-pattern
baldness (androgenic alopecia) is one thing, prostate disease
quite another — but DHT also stimulates the growth of prostate
cells, producing normal growth in adolescence but contributing to benign
prostatic hyperplasia (BPH) in many older men.
Scientists have taken advantage of the link between male pattern baldness
and BPH to develop a single medication for both conditions. Finasteride blocks
the conversion of testosterone to DHT; when taken in a 5-mg dose (Proscar),
it helps some men with BPH, and in a 1-mg dose (Propecia), it helps some
men with androgenic alopecia. A newer drug, dutasteride (Avodart),
has a similar effect on BPH but is not yet approved for baldness.
Is there another dark side to the DHT connection? Since DHT drives
both hair loss and the growth of prostate cells, do men with androgenic
alopecia have an increased risk of prostate cancer? Perhaps, according
to scientists in Australia. They evaluated 1,446 men who were diagnosed
with moderate to high-grade prostate cancer before age 70 and compared
them with 1,390 men of the same age who were free of the disease. Even
in the era of molecular biology, the research tool was simplicity itself.
The researchers looked at each man’s scalp, then used sophisticated
statistical methods to see if there was a link between hair loss and
prostate cancer. They found that men with bald spots at the top of their
heads (vertex baldness) were one and a half times more likely
to have prostate cancer than those without bald spots. The association
was particularly strong for men who were diagnosed with high-grade prostate
cancer at 60–69 years of age. In contrast, there was no link between
a receding hairline (frontal baldness) and cancer.
Levels of baldness
A. Frontal recession
B. Bald at the vertex
C. Near-total baldness
Although it may seem far-fetched, there are precedents for an association
between vertex baldness and disease in men. Harvard’s Physicians’ Health
Study found that men with bald spots were more likely to develop coronary
artery disease than men with full heads of hair. Mild vertex baldness
was linked to a 23% increase, moderate baldness to a 32% rise, and severe
baldness to a 36% increase in risk. As in the Australian study of prostate
cancer, frontal baldness was not associated with risk.
Although testosterone and DHT are the leading suspects, doctors don’t
know what accounts for the apparent associations between vertex baldness
and prostate cancer and heart disease. Although explanations are on the
thin side, there is no reason to think that hair loss itself is harmful
to the prostate or heart — though it may take a toll on some men’s
self-image. But, more research is needed to explore the connection between
hair loss and disease in men.
October 2004 Update
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