London: For the first time, scientists claim to have identified the symptoms associated with what has been termed late-onset hypogonadism or "male menopause" caused by a reduction in testosterone production in some ageing men.
However, unlike female menopause, which affects all women, the male menopause is relatively rare, affecting only two percent of the elderly men, and is often linked to poor general health and obesity, say the scientists.
A team from Manchester University, Imperial College London and University College London has based its findings on an analysis of the testosterone levels of 3,369 men between the ages of 40 and 79 years from eight European nations.
The scientists asked details about their sexual, physical and psychological health and found that only nine of the 32 candidate symptoms were actually associated with low testosterone levels, the most important being the three sexual symptoms -- decreased frequency of morning erection, decreased frequency of sexual thoughts and erectile dysfunction.
Their research concluded that the presence of all three sexual symptoms, together with low testosterone levels, was required to establish a diagnosis of male menopause though other non-sexual symptoms may also be present.
These other symptoms included three physical symptoms -- an inability to engage in vigorous activity such as running or lifting heavy objects, an inability to walk more than a km, inability to bend, kneel or stoop -- and three psychological symptoms -- loss of energy, sadness, and fatigue.
"The diagnosis of classical hypogonadism is corroborated by underlying diseases affecting the testes or pituitary gland, which controls testicular function, but this well-practiced diagnostic approach is frequently found wanting when dealing with the age-related decline of testosterone in elderly men who are prone to have a significant background of non-hormone-related complaints.
"Our findings have for the first time identified the key symptoms of late-onset hypogonadism and suggest that testosterone treatment may only be useful in a relatively small number of cases where androgen deficiency is suspected, since many candidate symptoms of classic hypogonadism were not associated with decreased testosterone levels in older men", team leader Prof Fred Wu of Manchester University said.
The research has also identified the thresholds of testosterone below which certain symptoms become increasingly prevalent. Documentation of levels of testosterone below these thresholds is required to confirm diagnosis of hypogonadism in symptomatic elderly men.
"It is therefore important to specify the presence of all three sexual symptoms of the nine testosterone-related symptoms we identified, together with low testosterone, in order to increase the probability of correctly diagnosing late-onset hypogonadism," Wu said.
The findings have been published in the `New England Journal of Medicine`.