Athletes are taking ever more health risks as they seek performance enhancing drugs that will not be picked up in doping tests, scientists say.
The city of Turin is preparing for the Winter Olympics
Experts say professionals are favouring substances such as growth hormones over easily-traceable anabolic steroids, the New Scientist reports.
Many Winter Olympic competitors have taken illegal drugs at some point in their careers, experts said in Turin.
Athletics chiefs admitted many drug users were going undetected.
The Winter Olympics start in Turin this weekend.
Chris Butler, of the International Athletics Federation said: "It's clear to everyone that athletes are willing to go that extra step.
"I wouldn't be surprised at anything they are taking - they've shown they are willing to take the risk."
Growth hormones (GH) are proving particularly difficult for anti-doping authorities to spot and also carry enormous risk.
GH are produced naturally in the body, where it promotes the growth of new muscle cells and increases the production of an insulin-type growth factor.
This in turn influences muscle, nerve, cartilage, bone and lung cells.
But some athletes take GH, often harvested from human cadavers, in quantities that would boost natural levels five or 10 times.
Although the substance can make a huge difference to an athlete's performance, using it at high concentrations for long periods can be fatal.
Symptoms of GH abuse also include arthritis, heart failure, and the enlargement of the jaw, hands and feet.
And there have been cases of people contracting CJD after injecting growth hormones either as a medicine or performance enhancer.
A spokesman for the anti-doping department of UK Sport, Russ Langley, said the health effects of banned drugs were often forgotten in the focus on performance enhancement.
"For a drug to be banned it has to fail two of three criteria - one of which is the impact on the health of the athlete.
"There have also been an increasing number of stories about the long-term effects of the use of anabolic steroids," he added.
'Cat and mouse game'
He also pointed out that synthetic GH were created for legitimate medical use - for someone with a health problem, not someone trying to boost their physical performance.
He added: "The sophistication of the cheaters is always improving, but so are the efficiency of the tests."
He says the processes and equipments that the labs use are always improving, but acknowledges it is always a "cat and mouse game".
It is hoped tests being used at the Winter Olympics will be able to detect whether athletes have injected synthetic forms of the hormones.
But they are only detectable for 20 to 30 hours after the injection.
The International Olympic Committee president Jacques Rogge has already said there will be a 72% increase in the number of drug tests at this year's games.
But University of Munich Hospital anti-doping expert Martin Bidlingmaier, who invented a test to detect synthetic GH, said the race between the cheats and the testers was one doping athletes are always winning.