Testosterone in Blood
Linked to Better Memory
Excerpt By Alison McCook, Reuter's Health

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 a protein.

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, Resnick added.

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 disease patients.

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.

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