| Testosterone in Blood
Linked to Better Memory
NEW YORK (Reuters
Health) - Older men with relatively
high levels of testosterone in their blood tend to outperform
others in tests of memory and other aspects of mental functioning,
according to new study findings.
The investigators noted a link between
mental functioning and levels of free-floating testosterone in
the blood, a form of the male sex hormone that is not bound to
Lead author Dr. Susan Resnick of the
National Institute on Aging in Baltimore, Maryland, told Reuters
Health that she is not sure whether testosterone itself helps
men retain some of their mental abilities into old age, or if
the hormone becomes converted into estrogen in the brain, and
it is the female hormone that boosts the organ's function.
Regardless, she said any treatment
based on increasing testosterone levels to improve memory will
be long in coming--if it ever appears.
Previous research has suggested that
testosterone can increase a man's risk of stroke, Resnick noted,
and higher amounts of the male hormone may even up the chance
of developing prostate cancer. Recent evidence demonstrating that
hormone replacement therapy in postmenopausal women can cause
more harm than good is a lesson to all researchers that investigations
into treatment involving hormones should proceed with caution,
Benefits and risks must be clarified,
she explained, before hormones could be used for treatment.
This is not the first study to report
a link between blood levels of free-floating testosterone and
memory in older men. One study demonstrated that men who received
a weekly injection of the male sex hormone seemed to experience
improvements in their spatial abilities and verbal memory. Another
study with rodents found that nerve cells exposed to testosterone
tend to produce a benign or beneficial form of a particular protein,
which is present in a harmful form in the brains of Alzheimer's
In the present study, reported in
the November issue of the Journal of Clinical Endocrinology &
Metabolism, Resnick and her team measured free-floating and protein-bound
levels of the male hormone in 417 men aged 50 to 91 years. The
researchers continued testing the hormone levels in the men for
10 years, during which time they also administered repeated tests
designed to measure different aspects of mental functioning.
Resnick's team found that men with
higher than average blood levels of free-floating testosterone
outperformed others in certain tests of mental functioning, but
not all of them. Specifically, men who showed higher levels of
male hormones scored higher in tests of visual and verbal memory,
during which they repeated word lists or drew an image they had
been shown before. The participants also outperformed their peers
during spatial tests where they matched shapes that were rotated
in different directions.
In an interview with Reuters Health,
Resnick explained that only the free-floating, and not protein-bound,
form of testosterone can reach the brain, where it would exert
its effects on memory.
Just how hormones influence memory remains unclear, she noted, but
previous studies have shown that hormones can affect how much blood
circulates to the brain, as well as the activity of nerve cells.
With so much still unclear, Resnick
emphasized that people should not turn to testosterone to avert
mental declines in old age. "We don't recommend that people go
out and buy that," she said.
SOURCE: Journal of Clinical Endocrinology
& Metabolism 2002;87:5001-5007.
Reference Source 89