Researchers found that testosterone therapy improved the sexual function, mood and walking ability of older men.
The study - co-led by Dr. Ronald Swerdloff, a researcher at the Los Angeles Biomedical Research Institute (LA Biomed) in California - reveals the results of the first three trials that form part of the Testosterone Trials (TTrials).
The TTrials are a set of seven double-blind, placebo-controlled studies that aim to determine the safety and effectiveness of testosterone treatment among men aged 65 and older.
The initial results suggest that over a 1-year period, daily application of a testosterone gel boosted blood testosterone levels of older men to levels normally seen in younger men, which improved their sexual function, mood and walking ability.
The results are likely to be welcome news for men, who often experience a reduction in testosterone levels as they age; levels of the hormone typically fall by around 1% annually after the age of 30 or 40.
Testosterone - primarily produced in the testicles - helps preserve men's muscle strength and mass, sex drive, sperm production, bone density, red blood cell production, fat distribution and facial and body hair.
As such, a reduction in testosterone may lead to reduced sexual function, physical changes - such as weight gain and reduced bone density, which can cause mobility problems - and emotional changes, including depression and a reduction in motivation and self-confidence.
Testosterone gel vs. placebo
While some studies have hailed testosterone therapy as effective for treating some of these problems in older men, other research has suggested the opposite, making it hard to draw conclusions about the treatment.
"Although testosterone treatment consistently increased muscle mass and decreased fat mass, effects on physical performance, sexual function, and energy have been inconsistent," say Dr. Swerdloff and colleagues.
The TTrials were launched to gain a better understanding of how testosterone therapy impacts men aged 65 and older who have low testosterone levels.
For the three trials - the Sexual Function Trial, the Physical Function Trial and the Vitality Trial - the researchers screened 51,085 men over the age of 65, identifying 790 men who had low testosterone levels and who met all other criteria.
The men were divided into two groups. One group was required to apply a testosterone gel - called AndroGel - daily for 1 year, while the other group applied a placebo gel daily.
At the start of treatment and 6, 9 and 12 months after, participants were required to complete questionnaires disclosing their sexual and physical function, as well as their vitality, mood and symptoms of depression.
Testosterone therapy improved all areas of sexual function
On analyzing the men's blood samples, the researchers found that those who received testosterone therapy demonstrated blood testosterone levels that were comparable to those of men aged 19-40.
Compared with men who used the placebo gel, the researchers found that those who used the testosterone gel experienced significant improvements in all areas of sexual function - including sexual desire, sexual activity and the ability to get an erection.
What is more, testosterone therapy also improved men's mood and symptoms of depression. While the treatment did not increase walking distance in the Physical Function Trial alone, it did increase the distance participants could walk within 6 minutes when the results of all three trials were considered.
The researchers identified no improvements in energy with testosterone treatment.
Across all three trials, the team found no differences in adverse events between men who received testosterone therapy and those who received the placebo. However, they stress that because there were a small number of study participants, no firm conclusions can be made about the safety of testosterone therapy.
"To fully evaluate the potential risks of testosterone treatment, a larger and longer study may be needed," notes study co-leader Dr. Christina Wang, also of LA Biomed.
Commenting on their findings, Dr. Swerdloff says:
"These initial results from the TTrials show some benefit from testosterone treatments in older men who have low testosterone levels.
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."
Last November, Medical News Today reported on a study suggesting that testosterone therapy may be beneficial for men with type 2 diabetes.