Testosterone can help some men get back a little of their loving feelings, and helps them feel better in general, according to a new study published Wednesday.
The effects are modest, and men didn't objectively get any more vitality, although they felt like they did, the government-funded study found.
It's the first study in years to show any benefit for testosterone therapy. The Food and Drug Administration has previously warned against over-promotion and overuse of testosterone replacement products, saying they can raise the risk of heart disease.
"This was the first time that a trial demonstrated that testosterone treatment of men over 65 who have low testosterone would benefit them in any way," said Dr. Peter Snyder of the University of Pennsylvania, who helped lead the study team.
"The trial showed that testosterone treatment of these men improved their sexual function, their mood, and reduced depressive symptoms—and perhaps also improved walking."
The FDA does not approve the use of testosterone to treat the effects of aging. But it's already a $2 billion industry, with millions of men buying gel, pills or getting injections.
Experts stress that the results, published in the New England Journal of Medicine,only apply to men over 65 who have medically diagnosed low testosterone. And it was a small trial, including fewer than 800 men, so it's not clear if their heart risks went up.
A few men had heart attacks or were diagnosed with prostate cancer during the study, but the rate were about the same in men who got real hormone and in those who got placebo cream.
Researchers across the country gave testosterone gel or a placebo cream to men who had demonstrated loss of the "male" hormone. They got enough to return testosterone levels to the mid-normal range for men 19 to 40 years old.
"Men in the testosterone group were more likely than those in the placebo group to report that their sexual desire had improved since the beginning of the trial," Snyder and colleagues wrote.
"Testosterone treatment showed no significant benefit over placebo with respect to vitality," they added.
"Men who received testosterone reported better sexual function, including activity, desire, and erectile function, than those who received placebo. Although the effect sizes were low to moderate, men in the testosterone group were more likely than those in the placebo group to report that their sexual desire had improved."
The effects on sexual performance were not as marked as erectile dysfunction drugs such as Viagra and Cialis, the researchers found.
"However, testosterone was associated with small but significant benefits with respect to mood and depressive symptoms. Men in the testosterone group were also more likely than those in the placebo group to report that their energy was better."
As men age, their bodies make less testosterone. It's not as sudden as when women lose estrogen, but the effects can be similar - loss of energy, sexual desire, depression and bone loss.
Dr. William Reilly, an orthopedic surgeon in Southlake, Texas, said it happened to him.
"I hit a brick wall when I was about 62 years old,"said Reilly, who is now 68.
"All of a sudden my energy level just wasn't the same. I'd wake up and I just felt tired and I'd be going to work and by the second case I'd be getting a little bit of brain fog," Reilly told NBC News.
He started getting less out of his gym workouts. "My arms were starting to get smaller. My belly was getting bigger," Reilly said.
So did Ed Stevens of Ft. Lauderdale, Florida.
"At about age 55, which was about almost eight years ago, I was fatigued, I was getting depressed — which is not like me," Steven said.
Stevens who at 63 would not be considered a candidate for the therapy according to the trial findings, said the hormone helped him feel better.
"I wouldn't call it a huge difference," he said. "I just saw over the months my body mass came back to where it was, my energy was better, libido was a little better."
Results are expected later from four other related studies, which tested the hormone's effects on mental function, bone density, heart function and anemia.
Read the full study article here.
