The male menopause is a real phenomenon that should be treated with testosterone replacement therapy, a study has concluded.
Men as well as women suffer a drop in sex hormones as they age, and also suffer from hot flushes, low libido, night sweats, joint pain and low mood, say researchers. Also known as the "andropause", symptoms can include depression, muscle weakness and an increase in body fat.
A study by the Centre for Men's Health in London, which has treated more than 2,000 men with testosterone over the past 26 years, said the majority of men benefited from therapy.
The authors of the study, published in the Journal of the Ageing, estimated that one in five men aged over 50 suffers from testosterone deficiency.
Prof Malcolm Carruthers, the centre's chief medical officer, said: "This study proves [the therapy's] effectiveness?... but most importantly supports the safety of testosterone treatment, even over prolonged periods."
Prof Carruthers has also called for better testing of testosterone, believing that some men would remain within the "normal range" and yet still be personally deficient.
"Contrary to orthodox theory, there is no threshold for testosterone levels. Resistance to the hormone could be caused by age, stress, obesity intake or genetic factors," he added.
A number of studies have linked low testosterone with obesity and diabetes, although scientists say it is too early to tell if hormone therapy could ease these conditions.
Recent research has also suggested that men with low testosterone levels are likely to die younger than men whose levels of the hormone are considered normal.
But some experts remain sceptical. "It doesn't appear to add much to a complex topic that cries out for a large blinded, randomised clinical trial," said Prof Jonathan Seckl from Edinburgh University.
Prof Frederick Wu, from the University of Manchester, added: "In my opinion this publication is not only misleading but potentially dangerous, particularly when the author calls for many more men to be treated, inappropriately, with testosterone."
The term andropause has been considered controversial because there does not seem to be a sudden moment where testosterone levels decline, as is the case for women. Instead, sex hormone levels in men gradually start to decrease from the mid 30s.
Some health experts believe the male menopause is in fact related to stress and anxiety usually triggered by a midlife crisis.