When I was an athlete competing at the Olympics, I was always of the belief that we were operating under a protective umbrella that the drugs testers were holding over our heads. I looked around the Olympic Village sure that if there were cheats then they stood a really good chance of being caught and that they had to really work to get around a system that was so good. Recent press coverage about Dwain Chambers and Marion Jones bolsters the view. They were cheating - they eventually got caught. But in reality the cheats are often slipping past the testers and my old attitudes seem hopelessly naive.

Human growth hormone (HGH) is naturally produced in the brain to help with muscle, cartilage and bone development, particularly when we are young. The original need for a laboratory product was for patients who had a deficiency, but as is so often the case, the body-building fraternity began in the early 1980s to experiment with it. At the beginning, the sports testers were way behind and those who wanted to could use HGH without fear of being caught. The drug worked well, with users reporting extra strength and lower body fat soon after starting a course.

By the 2000 Games in Sydney, the International Olympic Committee (IOC) had seemingly had enough. Rumours of athletes using the stuff were rife and it put millions of dollars into a study headed by Professor Peter Sonksen, a British endocrinologist and HGH expert who had designed a test that could detect HGH in someone's system up to three weeks after it had been injected. But the IOC did not use the test and whoever was using the stuff in Sydney slipped away.

Despite refining his test in time for Athens, the IOC chose another test, which, according to Sonksen, had a loophole a mile wide. “They introduced another test in Athens called the isoform test, but you've got to have a blood sample taken less than 24 hours after the athlete last injected himself in order to stand a chance of catching someone,” he said.

The IOC maintains today that the Sonksen test was neither reviewed by other scientists at the time nor validated independently in other laboratories, claims that Sonksen disputes. Perhaps understandably, the IOC is unwilling to say how long after drugs use its isoform test will catch HGH users. A statement issued to the BBC reads: “The IOC has full confidence in the test being used to detect HGH at the Olympic Games. The test was used in Athens and Turin and will be used again in Beijing this summer, where 450 tests will be conducted.” The number of people caught using HGH in Turin and Athens combined was zero.

Maybe this is a substance that is all rumour and gossip - what body-builders used in the Nineties did not cross the divide from gym to Games. But when I went to the US, the evidence was laid out in extraordinary detail. There, the Drug Enforcement Agency (DEA) was getting fed up with what it called an open pipeline from Chinese pharmaceutical companies to America. Where European pharmaceutical companies trade through the usual medical routes such as doctors and hospitals, the Chinese had no such compunction. Internet sites bloomed with offers to ship HGH and steroids to your door through DHL or UPS, the courier companies. The DEA reckons that HGH is being used by some people in every school and sports club across the country. When the agency went after big importers of the stuff it seized box after box of Chinese HGH.

Perhaps the US is suffering some epidemic that is yet to hit home here? After a visit to a needle exchange in Tyne and Wear that possibility, too, is dashed. It is an NHS advice and medical back-up centre, set up to help to cope with the heroin explosion in the early Nineties. But the man running it, Dr Rob Dawson, estimates that more than 40 per cent of his patients don't touch hard drugs. They are after a sporting edge and want steroids, insulin and HGH. Where HGH was once so expensive that only the most determined body-builder would add it to his drugs cocktail, Dawson calls HGH the new “food for the masses”.

I had to find out just how hard it was to get my own hands on HGH. I searched on Google for it and my BBC producer met a bloke in an ordinary pub. Within 24 hours I had a packet of Chinese HGH sitting on my desk. It cost £180 and would last an athlete about a fortnight. I sent two of the ten phials to be tested and found that it is indeed HGH and very good quality. The rest sits on my desk. I honestly don't know what to do with it but I have a feeling that there are plenty of people who do.

Growing pains

— Human growth hormone (HGH) has been used in Britain to help stunted children to grow since 1959. Some boys who would have reached a height of only 4ft 6in were able to grow to 5ft 9in.

— HGH is produced naturally by the brain’s pituitary gland. It is a protein substance that is emitted after exercise and during sleep and, while it is more abundant when people are young, it is produced throughout adult life.

— HGH has been used to prevent muscle wasting in Aids sufferers and as an anti-ageing agent. It is sold in vials that are injected by users.

Matthew Pinsent's full report into HGH is on Inside Sport on BBC One at 10.50pm.