Ball-and-stick model of the testosterone molecule, C19H28O2, as found in the crystal structure of testosterone monohydrate. Credit: Ben Mills/Wikipedia

As men age, their testosterone levels decrease, but prior studies of the effects of administering testosterone to older men have been inconclusive. Now, research shows that testosterone treatment for men over 65 improves sexual function, walking ability and mood, according to a study published in the New England Journal of Medicine by a team of researchers that included lead researchers from Los Angeles Biomedical Research Institute (LA BioMed).

Researchers conducted the Testosterone Trials (TTrials), a coordinated group of seven trials, and have analyzed the results of the first three regarding its impact on sexual function, physical function and vitality. They found that testosterone treatment increased the blood testosterone level to mid-normal for young men.

Testosterone also improved all aspects of sexual function, including sexual activity, sexual desire and the ability to get an erection. Testosterone treatment did not significantly improve distance walked in six minutes when only men enrolled in the physical function trial were considered, but did increase the distance walked when all men in the TTrials were considered. The treatment did not improve energy but did improve mood and depressive symptoms.

"These initial results from the TTrials show some benefit from testosterone treatments in older men who have low testosterone levels," said Ronald Swerdloff, MD, a lead researcher at LA BioMed. "While these initial findings are encouraging for men with low testosterone levels, the TTrials will continue to analyze the data to determine whether testosterone treatment improves cognitive function, bone density, cardiovascular health and anemia, as well as the risks of testosterone treatment."

Drs. Swerdloff and Christina Wang, MD, led the study at LA BioMed, where research volunteers have participated in the multi-center TTrials.

In 2003, the Institute of Medicine reported that there was insufficient evidence to support any beneficial effect of testosterone in such men. This report was the impetus for TTrials, which are now the largest trials to examine the efficacy of testosterone treatment in men 65 and older whose testosterone levels are low due seemingly to age alone.

TTrials researchers screened 51,085 men to find 790 who qualified with a sufficiently low testosterone level and who met other criteria. The men enrolled were randomized into two groups: one to take a daily testosterone gel and the other a daily placebo gel, for one year. Efficacy was then evaluated at months three, six, nine and 12. Sexual function was assessed by questionnaires. Physical function was measured by questionnaires and the distance walked in six minutes. Vitality, mood and depressive symptoms were also evaluated using questionnaires.

Across the three trials, adverse events - including heart attack, stroke, other cardiovascular events and prostate conditions - were similar in men who received testosterone and those who received placebo. However, the number of men in the TTrials was too small to draw conclusions about the risk of testosterone treatment.

"To fully evaluate the potential risks of testosterone treatment, a larger and longer study may be needed," said Dr. Wang.

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