WEDNESDAY, June 16 (HealthDay News) -- In describing a set of concrete symptoms for "male menopause" for the first time, British researchers have also determined that only about 2 percent of men aged 40 to 80 suffer from the condition, far less than previously thought.

Male menopause, also called "andropause" or late-onset hypogonadism, supposedly results from declines in testosterone production that occur later in life, but there has been some debate on how real the phenomenon is, the study authors noted.

"Some aging men indeed suffer from [male menopause]. It is a genuine syndrome, but much less common than previously assumed," concluded Dr. Ilpo Huhtaniemi, senior author of a study published online June 16 in the New England Journal of Medicine.

"This is important because it demonstrates that genuine symptomatic androgen deficiencies [androgens are male hormones] is less common than believed, and that only the right patients [should] get androgen treatment," added Huhtaniemi, a professor of reproductive endocrinology in the department of surgery and cancer at Imperial College London.

Many men have been taking testosterone supplements to combat the perceived effects of aging, even though it's not clear if taking these supplements help or if they're even safe. The result has been mass confusion, not only as to whether male menopause exists but also how to treat it.

"A lot of people abuse testosterone who shouldn't and a lot of men who should get it aren't," said Dr. Michael Hermans, an associate professor of surgery in the Texas A&M Health Science Center College of Medicine and chief of the section of andrology, male sexual dysfunction and male infertility at Scott & White in Temple, Texas.

For this study, the research team, from Imperial College London and the University of Manchester, measured testosterone levels in 3,369 men aged 40 to 79 and then correlated these levels with different symptoms.

Of 32 possible symptoms, only nine were linked with decreased testosterone levels. Three were physical -- not being able to engage in strenuous physical activity, not being able to walk more than 1 kilometer and not being able to bend over or kneel -- and three were psychological -- low energy, sadness and fatigue.

But these six symptoms were only peripherally linked to low testosterone levels.

Three sexual symptoms -- less frequent morning erections, lower sex drive and erectile dysfunction -- were more robustly related to testosterone levels.

Men need to have all three sexual symptoms plus measurably lower levels of testosterone to qualify for the diagnosis of late-onset hypogonadism, the authors stated.

But even with this new diagnostic criteria, the challenge of treating men with sexual and other symptoms of male menopause is still far from straightforward.

"These symptoms that are associated with hypogonadism are not necessarily going to be treated by testosterone therapy," pointed out Dr. Natan Bar-Chama, director of male reproductive medicine and an associate professor of urology at Mount Sinai Medical Center in New York City. "We know very well that erectile dysfunction is complicated. It's associated with other co-morbidities and the ability to regain normal erectile function is often not successfully treated with just testosterone."

"Just because an older guy comes in and says he has a bad sex life, you don't automatically give him testosterone," Hermans added.

And even though there are any number of testosterone products available -- from patches to pellets -- there isn't much research on how much they really help men, Hermans said, or whether they are safe.

More information

The U.S. National Library of Medicine has more about hypogonadism.