As men age, their sexual function, vitality and strength can decline, but researchers had not yet established whether testosterone treatment is actually beneficial. Now, a team that included UF Health researchers has established testosterone's benefits in a study published yesterday (Feb. 17, 2016) in the New England Journal of Medicine. The paper examines the first three of seven trials in a long-term study called The Testosterone Trials, or the TTrials. In this first study, researchers analyzed the results of the first three trials, which examined sexual function, physical function and vitality, including mood and depressive symptoms, walking speed and walking distance.

The researchers found that the treatment increased the blood testosterone level from moderately low to mid-normal in men ages 19-40 and improved all aspects of sexual function, including sexual activity, sexual desire and the ability to get an erection.

"The study reinforced the results we expected to see, except for walking speed," said Marco Pahor, M.D., the director of the UF Institute on Aging and a co-author of the paper.

In 2003, the Institute of Medicine reported there was not enough evidence to support a beneficial effect of testosterone in men who have low levels of the hormone. This report was the impetus for the TTrials, which are now the largest trials to examine the use of testosterone treatment in men 65 and older whose low testosterone levels can be attributed to age alone.

"The results of the TTrials show for the first time that testosterone treatment of older men who have unequivocally low testosterone levels does have some benefit," said Peter J. Snyder, M.D., the principal investigator of the TTrials and a professor in the division of endocrinology, diabetes and metabolism at the University of Pennsylvania's Perelman School of Medicine. "However, decisions about testosterone treatment for these men will also depend on the results of four other trials -- Cognitive Function, Bone, Cardiovascular and Anemia -- and the risks of testosterone treatment."