A new study suggests that men with low levels of testosterone are more likely to die young; they apparently have a 33% increased risk of death over an 18-year period than those with higher levels.
The researchers at the University of California’s San Diego School of Medicine, say such men are less likely to reach middle age compared with those who have high levels of the male sex hormone.
The study findings provide more evidence that there may be a case for some men being placed on "testosterone replacement therapy" - the male equivalent of hormone replacement therapy in women.
The decline in the levels of the hormone is called the andropause or male menopause.
The researchers said it was too early, however, to recommend that vulnerable men use testosterone patches.
The study's lead author Dr. Elizabeth Barrett-Connor, says though the findings have very exciting and important implications, they are not advocating that men should take testosterone to prolong their lives.
Dr. Barrett-Connor suggests it is possible that lifestyle determines the level of a man's testosterone and it may be that testosterone levels can be altered by lowering obesity.
Testosterone is a hormone produced in the testes; it triggers the onset of puberty and is closely associated with the libido.
Experts say testosterone levels vary widely from man to man and often fall with age and fatherhood.
Low testosterone levels have been associated with a lower sex drive, mood swings, weaker muscles and a greater risk of osteoporosis.
For the study the researchers examined the medical histories of 800 Californian men, aged 50 to 91, who were taking part in a chronic disease study started in the 1970s.
It was found at the start of the 1980s that a third of the men had unusually low testosterone levels for their age.
The difference could not be explained by smoking, drinking, physical activity or pre-existing illnesses such as heart disease and diabetes and this group of men had a 33 per cent greater risk of dying during the next 18 years than the men with high testosterone levels.
The researchers say why low testosterone is linked to premature death is unclear but men with the lowest levels were more likely to be obese, have high blood pressure and high levels of "bad" cholesterol.
Experts say levels of testosterone in men of all ages are falling and the study is of interest because of the association with metabolic syndrome, the risk factors for which include waist measurement over 102 cms, high levels of cholesterol, high blood pressure and high blood sugar.
They say the use of testosterone supplements is a contentious one because of the potential side effects.
The team presented their findings at the Endocrine Society conference in Toronto.