A preliminary study of testosterone therapy in older men with low levels of the hormone and clinical conditions to which low testosterone might contribute, found that restoring levels to those of healthy young men improved sexual function. Treatment had a smaller effect on other aspects of health, such as the ability to walk or the sense of vitality.

These initial results of the Testosterone Trials (T Trials), a group of studies supported primarily by the National Institutes of Health, appear in The New England Journal of Medicine on February 18, and report the results of the first three of seven double-blind, placebo-controlled trials.

A high proportion of older men have testosterone levels well below those found in healthy younger men. In most cases, these low levels are not due to diseases known to affect testosterone levels, such as testicular or pituitary conditions. Many of these men also have symptomatic problems that could be related to low testosterone, including diminished sexual function, decreased mobility and fatigue. The T Trials were designed to determine if testosterone treatment would alleviate these symptoms. Such trials were recommended by the Institute of Medicine (now the National Academy of Medicine) as a key step before considering possible larger and longer trials that would be needed to assess long-term risks and benefits of testosterone treatment for older men. The National Institute on Aging (NIA), part of NIH, initiated the T Trials in response to this recommendation.

The findings were reported by principal investigator Peter J. Snyder, M.D., Perelman School of Medicine at the University of Pennsylvania, Philadelphia, and colleagues, who conducted the study at 12 sites across the US. The studies were funded primarily by NIA, with additional support from the National Heart, Lung, and Blood Institute, the National Institute of Neurological Disorders and Stroke, and the Eunice Kennedy Shriver National Institute of Child Health and Human Development, all part of NIH. Additional funding, and the study drug and placebo, were provided by AbbVie Pharmaceuticals.

“For a long time, there has been interest in whether testosterone is an appropriate therapy for aging-related conditions in men,” said NIA director Richard J. Hodes, M.D. “This study clarifies questions about some of its potential benefits. As the researchers note, clarifying the risks requires further study.”

Participants included 790 men age 65 and older with serum testosterone levels consistently well below the average for young healthy men. They were randomized to receive testosterone gel applied to the skin or a placebo gel daily. Serum testosterone concentration was measured at one, two, three, six, nine and 12 months. The men were also closely monitored for prostate and cardiovascular problems. In addition to low testosterone, the presence of at least one of three conditions (low sexual function, difficulty in walking or low vitality) was required for eligibility to participate in the trials. The results on these outcomes are reported in the current paper. Effects on other outcomes (cardiovascular, bone density, cognition and anemia) will be reported in future papers.

Sexual function — In men with low sexual function, testosterone treatment increased sexual activity, sexual desire and erectile function more than placebo treatment. Change was measured by differences in scores on three standard sexual function questionnaires.

Physical function — In men with difficulty walking, testosterone treatment did not significantly affect walking ability, as measured by the distance they could walk in six minutes (a common test of walking ability) among those enrolled in the physical function trial. However, in all men in the three trials, walking speed and distance did improve among those who received testosterone compared with those who received placebo.

Vitality — In the group of men with symptoms of low vitality and fatigue, testosterone treatment did not significantly affect fatigue symptoms, but had modest favorable effects on mood. Despite a minimal reported difference between those treated and those on placebo, men in the testosterone-treated group were more likely to report that their energy was better at the end of the trial than men in the placebo group.

T Trials participants experienced few adverse effects of testosterone treatment, however too few to draw conclusions about risks in older men, particularly since men considered at high risk for prostate cancer and cardiovascular disease were excluded from the trial. A larger and longer study would be needed to assess risk of harm from testosterone therapies in older men. Three men in the testosterone group and one in the placebo group were diagnosed with prostate cancer during the trial and in the year following. The study did not find a pattern of increased cardiovascular disease risk.

“The trials’ results indicate that, for older men with low sexual function, testosterone treatment can contribute to improved function,” said Evan Hadley, M.D., director of NIA’s Division of Geriatrics and Clinical Gerontology. “In contrast, though, the results don’t indicate that testosterone treatment for older men with low walking ability or vitality will improve these conditions to a great extent. Additional trial arms tested effects on other aging-related outcomes, and we are looking forward to their results to help provide further insights into testosterone use in older men.” Older men should consult their physicians if considering a testosterone treatment, Hadley emphasized.