Researchers have identified the symptoms linked to "male menopause," which results from low testosterone production in aging men.
Unlike female menopause, which affects all women and usually begins in the 40s and onward, male menopause only affects two percent of elderly men and is often linked to poor general health and obesity.
Out of nine symptoms associated with the disease, the three most important included decreased frequency of morning erection, decreased frequency of sexual thoughts (or sex drive), and erectile dysfunction, the researchers said.
These symptoms together with low testosterone levels are required to establish a diagnosis of late-onset hypogonadism, or male menopause, they added in the study.
The research by the University of Manchester, Imperial College London, UCL (University College London) and other European partners, was published in the June 17 issue of the New England Journal of Medicine.
The findings should provide new guidance to physicians prescribing male testosterone therapy to aging men with dwindling sex drive, researchers said.
Testosterone therapy has increased by 400 percent in the United States since 1999 but not at all in other developed nations, they added.
For the study, researchers measured testosterone levels in 3,369 men between the ages of 40 and 79 years from eight European centers and asked details about their sexual, physical and psychological health.
Other non-sexual, physical symptoms associated with male menopause include an inability to engage in vigorous activity, such as running or lifting heavy objects, an inability to walk more than one kilometer, and an inability to bend, kneel or stoop.
Psychological symptoms include loss of energy, sadness, and fatigue, although the three had minimal links to low testosterone, researchers said.