A new study suggests that testosterone treatment might only bring about a modest improvement in the sex lives, walking strength and mood of a select group of older men, Fox News reports.

The researchers emphasized that the findings apply only to use of testosterone gel by men 65 and older with low hormone levels and related symptoms.

The benefits of testosterone treatment in younger men are unknown.

Lead author Dr. Peter Snyder, a University of Pennsylvania hormone specialist, said it would be premature to recommend the treatment even for men like those studied.

"Making a recommendation depends on knowing all the benefits versus risks," he said.

"We still don't know everything we want to know."

For the study, the researchers studied almost 800 men 65 and older at 12 centers nationwide who had low blood levels of testosterone.

They were randomly assigned to use testosterone gel or fake gel without hormones, rubbed daily on the skin for a year. They had to fill out questionnaires and take a six-minute walking test.

The study found that there was only a modest improvement in sex lives among the testosterone group and only a slightly greater improvement in mood and strength among the testosterone group than the other men.

The current results are in Thursday's New England Journal of Medicine.

The new research combines results from three of the government-funded studies.

Results from the four other studies, which tested the hormone's effects on mental function, bone density, heart function and anemia, are expected at a later date.