Drug testing is scheduled to begin this summer on the U.S. and European PGA tours. But one drug that won't be tested for is one of the drugs that is most in the news these days: human growth hormone, or HGH.

The introduction of random drug-testing was seen as a way of silencing the whispers about drug use in the sport, but now it has emerged that when the system goes live on July 1 the golfing authorities will not even be testing for HGH, despite evidence that it is one of the most widely abused performance-enhancing drugs in sport.

The omission opens the door for potential cheats to avoid steroids but to take the hormone without fear of being caught. Although HGH appears on golf's list of banned substances, both the European and PGA Tours have confirmed that players will only be required to submit urine samples. However, HGH can be detected only by taking blood samples.

The article in the London Telegraph notes that Butch Harmon last week said he believed some golfers have used or are using HGH:

"We would be pretty naive to think that someone hasn't taken a growth hormone or a steroid just to allow themselves to recover from injuries or to hit more balls, and [make] your body react better," said Harmon in an interview with Golf World magazine.

There is no suggestion that any of Harmon's pupils have used performance-enhancing substances, but Woods agreed with his former coach's views earlier this week. "I think we would be very naive to say that someone has never tried it in our sport," the world No 1 said.

"Everyone has tried it in most sports. There is no reason to think why someone hasn't."