Testosterone really can help reverse the ageing process in men, researchers claim.

It will come as welcome news for pop star Robbie Williams, who recently admitted to injecting himself with the sex hormone twice a week to boost his sex drive and slow the march of time.

Williams, 37, was offered the treatment after doctors told him he had the sex drive of a 100-year-old man.

And it appears the treatment has more benefits than helping in the bedroom department, with the superstar admitting: “It has changed my life. I feel I’m getting a second wind.”

Loss of muscle tissue is a typical symptom of ageing, and is also associated with diseases such as Aids and cancer.

It can be treated using anabolic steroids – but these can have unwanted side-effects, making testosterone replacement a healthy alternative.

The new research, published in BioMed Central’s open access journal Immunity and Ageing, shows that nine proteins in the blood alter with age.

However, the profile of some of these proteins can be reversed by testosterone treatment, and prevent the loss of muscle mass.

Researchers from Boston University School of Medicine and University of Texas Medical Branch in the United States compared protein levels in serum samples from two groups of healthy men.

One group were aged 18 to 35 and the other were older men, aged 60 to 75.

The older men were found to have reduced levels of seven proteins, which were either growth factors, or were involved in immune response and pro-collagen.

In contrast the monokine MIG, also involved in immune activity, was elevated.

Testosterone treatment increased lean muscle mass and levels of the appetite suppressing hormone leptin, for both groups of men.

The hormone also increased levels of pro-collagen and growth protein IGF-1 in young men and the researchers saw a similar increase in a small group of older men.

Dr Monty Montano said: “The blood proteins we found that altered with healthy ageing also have links to maintenance of muscle, such as IGF-1 and pro-collagen, or are involved in regulation of the immune system, possibly reducing T-cell and neutrophil responses with age.

“Additionally all of the proteins we found are involved with the signalling pathways controlled by proteins which are known to be associated with ageing.

“It is no simple matter to find a one size fits all test for ageing. Our results suggest that there is a difference in response to anabolic steroids between young and older men, despite both groups increasing in muscle mass.

“It seems that testosterone replacement does not necessarily mean a restoration of full testosterone functionality for the older man.”