BERLIN, Germany (CNN) -- Heidi Krieger proved herself one of the world's top athletes in the 1980s, winning medal after medal in the shot put for East Germany.

Andreas Krieger says his body changed soon after he began taking what coaches said were vitamins.

Now, the former sports star looks disdainfully at the awards, dismissing them as "doping medals" and honors that turned a woman into a man.

Heidi Krieger, the 1986 European women's shot-put champion, became Andreas Krieger after a sex-change operation in 1997. He says he had been fed so many steroids by his coaches without his knowledge that physical and emotional problems began.

The young woman's physique changed drastically, as did her feelings. "I felt much more attracted to women and just felt like a man. But I knew I was not lesbian," Krieger told CNN.

Her coaches said they were giving her vitamin pills, but they were actually feeding her Oral-Turinabol anabolic steroids. Watch how Krieger's body changed »

Krieger is among an estimated 10,000 East German athletes thought to have been given performance-enhancing drugs to help build their country into a sports powerhouse.

In the 1970s and 1980s, the German Democratic Republic was one of the most successful Olympic Games nations. But after the fall of Soviet Communism, it was revealed just how much steroids were fueling the medal machine. Sports leaders, including Manfred Ewald, the head of East Germany's National Olympic Committee from 1973 until 1990, were convicted in the doping programs.

Krieger, who is now married and runs an army surplus store, says he has taken his life into his own hands and does not want to be seen as a victim.

But he and other former East German athletes tricked by their coaches are worried that too little has been learned from their plight.

Doping remains a major issue in sports, and many drug tests will be conducted in Beijing, China, as officials try to catch any cheats hoping to go undetected and get Olympic glory.

Experts say the next step for sportsmen and women looking for an illegal boost to physical performance could be gene therapy -- so-called "gene doping."

Sports physician Willi Heepe said gene therapy means the body will basically dope itself.

If that happens, "the human monster will be a reality," he told CNN.

Krieger is worried that the pressure to win could create new victims.

"If today's athletes say they want to take the risk, they really don't know what risk they are taking," he said.

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