A new research has linked low testosterone levels to a heightened risk of premature death from heart disease and all causes.
The finding refutes received wisdom that the hormone is a risk factor for cardiovascular disease.
Researchers base their findings on 930 men, all of whom had coronary artery heart disease, and had been referred to a specialist heart centre between 2000 and 2002.
heir heart health was then tracked for around 7 years.
On referral, low testosterone was relatively common. One in four of the men was classified as having low testosterone, using measurements of either bioavailable testosterone (bio-T) - available for tissues to use - of under 2.6 mmol/l or total testosterone (TT) of under 8.1 mmol/l.
These measures indicate clinically defined testosterone deficiency, referred to as hypogonadism, as opposed to a tailing off in levels of the hormone as a result of ageing.
During the monitoring period almost twice as many men with low testosterone died as did those with normal levels. One in five (41) of those with low testosterone died, compared with one in eight (12pc) of those with normal levels.
The only factors that influenced this risk were heart failure (left ventricular dysfunction), treatment with aspirin or a high blood pressure drug (beta blocker) and low bio-T levels.
A low bio-T level was an independent risk factor for premature death from all causes and from heart disease, after taking account of other influential factors, such as age, other underlying health problems, smoking and weight.
Borderline levels of low total testosterone (15.1mmol/l) also increased the risk of an early death.
While high doses of testosterone found in anabolic steroids are harmful to health, the evidence suggests that low, rather than high, levels of the hormone, are associated with obesity, risky blood fats, and insulin resistance, all of which are risk factors for diabetes and heart disease, say the authors.
Men at high risk of these diseases may stand most to gain from testosterone replacement, they suggest.
The study has been published online in Heart.