To many, Dan Hegarty's experience of hitting his 40s sounds familiar: he was tired, irritable, his body ached and he had lost his zest. "I would have a lull in my energy levels," he says. "My concentration wasn't great - I couldn't even concentrate on a newspaper. I wasn't sleeping well, and my libido had dropped off."Today, that is a distant memory, thanks, he believes, to testosterone gel.He says he feels younger, energetic and less tired."It makes you feel better and livelier, and your confidence comes back," says Hegarty, now 60.The treatment has also had a positive effect on his libido. "If you're tired all the time, it doesn't help with action in the bedroom."Testosterone use is soaring - prescriptions have more than doubled in 10 years, says Pulse magazine.The synthetic form of the hormone, derived from plants, can be given through injections, gels, lozenges or creams. And it's not just for men: women are taking it to help with flagging sex drive, low energy and mood.But many doctors say symptoms of low testosterone would be better addressed with lifestyle changes - for example, losing weight, exercising and reducing alcohol intake. - ©The Daily Telegraph..