By Gene Cherry

RALEIGH, North Carolina (Reuters) - Olympic and world 400 meters champion LaShawn Merritt has failed three doping tests for a banned substance and accepted a provisional suspension, his lawyer said on Thursday.

"LaShawn Merritt has accepted a provisional suspension as a result of positive drug tests caused by his use of an over-the-counter male enhancement product," the American athlete's attorney Howard Jacobs said in a statement.

"His voluntary acceptance of a provisional suspension means that he has chosen not to compete until the case has been decided," the statement added.

The U.S. Anti-Doping Agency (USADA) confirmed the positives contained prohormones of the banned male sex hormone testosterone and said in an email to Reuters its investigation of Merritt's case was continuing. It will have no further comment until the legal process was complete, a spokeswoman said.

"I am disgusted by this entire episode," USA Track & Field (USATF) chief executive Doug Logan said in a statement.

Merritt won individual 400 meters gold at the 2008 Olympics and 2009 world championships and led the U.S. to victory in the 4x400 meters relay in both competitions.

His victory by almost a second over defending champion Jeremy Wariner at the Beijing Games was the largest winning margin in the event for over 100 years.


Merritt's statement said he had used the over-the-counter product, which contained DHEA and pregnenolone, following the 2009 season.

"(It) caused LaShawn Merritt to test positive on three successive tests in October 2009, December 2009, and January 2010," the statement said.

Merritt, who asked for forgiveness for his mistake, was not notified of the positive tests until March.

DHEA (dehydroepiandrosterone) is an endogenous hormone and serves as precursor to male and female sex hormones (androgens and estrogens), according to the website for the Mayo Clinc (http://www.mayoclinic.com)

Because it is a testosterone precursor in the category of anabolic agents, it is prohibited under the anti-doping code.

"To know that I've tested positive as a result of product that I used for personal reasons is extremely difficult to wrap my hands around," Merritt said in a separate statement.

"I hope my sponsors, family, friends and the sport itself will forgive me for making such a foolish, immature and egotistical mistake.

"Any penalty that I may receive for my action will not overshadow the embarrassment and humiliation that I feel inside."

Logan, the USATF chief executive, said Merritt had brought shame to his sport.

"Any professional athlete in this sport knows that they are solely responsible for anything that goes into their bodies," Logan said in a statement.

"For Mr. Merritt to claim inadvertent use of a banned substance due to the ingestion of over-the-counter supplements brings shame to himself and his team mates.

"He has now put his entire career under a cloud."

(Editing by Ed Osmond/Greg Stutchbury)