Men participating in the study had low to normal testosterone levels, were at least 60 years old and were functioning at a relatively high level to begin with. It's still unclear how long-term use of testosterone might affect frailer and more disease-prone elderly men, researchers noted.
"But it's really not clear that in otherwise healthy, functional men in that low-normal physiologic range that using testosterone either alone or in combination with exercise added much."
The new findings, she said, suggest that testosterone "is widely used in people where it really may not be appropriate or may not provide the benefits that people think it's going to."
Abbott donated the testosterone gel used in the study, Androgel. The gel is approved by the U.S. Food and Drug Administration for men who make too little testosterone on their own, a condition called hypogonadism.
Because testosterone levels decline naturally as men age, some researchers have wondered if treating older, healthy men with the hormone could help slow changes in body composition and loss of strength.
To try to answer that question, Hildreth and her colleagues randomly assigned 167 older men to use testosterone or a hormone-free placebo gel each day and to do strength-training three times a week or not.
Use of testosterone was tied to a two-pound decrease in fat mass and a two-pound increase in muscle mass, the study team reported in The Journal of Clinical Endocrinology & Metabolism.
Men who weren't told to exercise also saw improvements in upper body strength during a year of testosterone use, compared to placebo gel users.
Exercise alone led to improvements in body composition — but testosterone and strength training did not appear to have an additive benefit, the researchers found. And with or without an exercise program, testosterone gel did not improve men's daily functioning in tasks like climbing stairs or getting up from a chair.
Studies have come to contradictory conclusions on the effect of extra testosterone on men's health and physical abilities, Hildreth's team noted.
"A number of studies have shown consistent improvements in body composition — but they don't seem to translate into significant improvements in function," Hildreth told Reuters Health.
Some research has suggested that although testosterone may help improve muscle strength in frail, elderly men, the effects don't last after treatment stops (see Reuters Health story of Dec 3, 2010 here: http://reut.rs/jt9Tvr).
AbbVie, a spinoff from Abbott that markets Androgel in the U.S., was not able to not provide a comment before press time.
Men in the current study seemed to tolerate testosterone well, Hildreth noted. But there are still long-term concerns about side effects, such as abnormal blood counts and elevated prostate specific antigen levels.
"People should be careful about using it," she said.
SOURCE: http://bit.ly/14CRScA The Journal of Clinical Endocrinology & Metabolism, online March 26, 2013.