Professor of medicine and endocrinology at Britain's Manchester University, Prof Wu said the European male ageing study (2003-05) showed the prevalence of the low-testosterone condition, which had the correct name of late-onset hypogonadism, was 2.1%.
Surprising many, researchers found no link between the condition and irritability, depression, or moods, said Prof Wu, the study's lead investigator.
The only significant links were with sexual performance and lack of sexual desire. A weaker but important link was found with frailty in old age.
A higher prevalence of the condition was found in the overweight, and those with diabetes, cardiovascular disease or general poor health.
Although any cause and effect relationships between the condition and poor health were not established, the finding was important for public health messages and for clinicians treating older men, Prof Wu said.
Establishing the level of testosterone loss considered to constitute the condition was "hotly debated" in the endocrinology community, Prof Wu said. Testosterone declined in all men with age, but whether "ageing itself" caused the "male menopause" was uncertain.
A follow-up check of the study cohort in 2008-10 was being analysed and the results were yet to be released.
Promising though mixed results in a testosterone hormone therapy trial showed possibility for future treatments, Prof Wu said.
A later United States-based trial of testosterone therapy had had to be halted because of cardiovascular deaths, indicating there was an unsafe level of hormone replacement. The earlier trial with a lower dose carried few side effects.
Speaking to the Otago Daily Times, Prof Wu indicated he disliked the "male menopause" label because the condition was not comparable to the hormonal changes experienced by women, but the term had caught on with the public.
Prof Wu visited New Zealand as the Freemasons Roskill Foundation 2011 distinguished speaker.
