The research, published in journal Immunity and Aging, revealed that the nine proteins change as the individuals get older. This process can be reversed by testosterone treatment in some of the proteins.
Testosterone therapy was seen to increase lean muscle mass and levels of appetite suppressing hormone leptin in both older and younger men.
Researcher Dr Monty Montano said: "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."
Meanwhile, research from the University of Sydney found that a decline in the testosterone levels of older men is likely to be a result, rather than a cause, of ageing.
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