In July 1977, an East German woman shot putter, Ilona Slupianek, was disqualified from the European Cup track and field finals in Helsinki when it was found that she had been using anabolic steroids, called "Anabolika" in German.

Use of these drugs by athletes in international competition is banned, and the episode in Helsinki seemed to confirm what a lot people believed about the East German sports program - that its extraordinary success in international and Olympic competition, especially by women, was built at least in part on the secret use of steroids.

Last December, even more convincing evidence surfaced when a young woman sprinter, Renate Neufeld, defected to the West and brought with her some pills and powder that she said her East German coaches had been forcing her to take. They were analyzed here and found to be steroids.

Despite these two episodes, there remains much mystery about precisely how extensive steroid use is in the hightly secretive East German training program, and how big a role it plays in winning the gold at the Olympics.

Dr. Alois Marder, a former East German sports doctor who defected to the West five years ago and now works at a West German sports medicine institute in Cologne, is one of those with first-hand knowledge of the situation, at least as it was before 1975.

Marder says steroids were used regularly but with relatively few athleted. "It was not very widespread," he said in a recent interview. "There was a small number of people because it is difficult to use such a noticeable practice. It is also difficult to say with any precision what is the influence on performance, so its use is not common with a lot of people."

In both cases, Marder notes, the problem for Communist East Germany is one of security. "High performance sports in East Germany are a problem for the government because people are trained for propaganda and not only for their own performance."

Training, he says, therefore "becomes a problem for state security, so they keep it quiet." The atheletes themselves, he adds, also have an obvious reason for keeping quiet about it.

But Marder and other western doctors, includin West German sports medicine specialist Dr. Adolf Metzner, do not believe that East Germany has any monopoly on steroid usage, and feel the balance between East and West in the matter is fairly even.

Marder also suggests it would be wrong to overestimate the impact of steroid usage on East German success. "The most important thing is the perfect organization of their training system over many years and their success in scientific research on athletic performance capabilities," he said.

"Seventy to 80 percent is talent. Twenty or 25 percent is training and maybe 5 percent is attributable to other influences, including drugs. True," he said, "if you can improve by 1 or 2 percent you can go from sixth to first place."

But Marder believes such improvements and whether they are drug-related are extremely hare to measure and says there is disagreement in medical circles over this.

On balance, he says, "I think drugs have more influence than some say, but not as much as others portray. But in the elite sports - track and field events or swimming - you cannot dismiss it out of hand."

The "perfect" system that Marder talks about is, indeed, extraordinary to behold. The East German sports machine, in brief, involves a nationwide Junior Olympic every two years to make sure no young talent slips through the cracks, a system of special sports schools and clubs where youngsters are taken out of normal schools, and in many cases family life, and drilled in those areas in which scientific evaluations have shown their greatest strengths and skills lie.

Sports medicine is more highly developed in East Germany than any where else, with doctors using bone scans and family history to analyze growth, blood samples to analyze stamina and exhaustion levels and training schedules that make no differentiation between men and women.

All of this is headquartered at the University for Physical Culture at Leipzig, where sports doctors and coaches for all activities down to the grade-school level are turned out in quantity.

In 1976, during one of the rare visits to this school allowed Western journalists, Dr. Kurt Tittel, head of the Sports Medicine Department, was fequently asked about steroids.

Tittel's usual answer was that East German atheletes are "developed" without steroids, a reply that might leave room at least for experimentation.

Neufeld, however, says "it was definitely not experimental, but part of the training program." Though she does not claim detailed knowledge outside of her East Berlin club, she says she believes with some certainty that steroids are widely used among world-class athletes in endurance sports in East Germany, including the Leipzig School.

Neufeld said in a recent telephone interview, however, that the use of such steroids "is not something that is discussed" among athletes. "Maybe among really good friends," she said, "but I never heard it spoken of."

One reason, she said, "is that the athletes don't know what they take. They are given pills as part of the training program. The pills are in a little bottle marked 'vitamins,' without any ingredients named."

Neufeld, 20, noticed unpleasant side effects from her "vitamins" - hardened leg muscles, occasional loss of voice, a thin growth of hair on her upper lip and a disrupted menstrual cycle - and when she was harassed over her rejection of the pills and other matters, she fled to the West with her Bulgarian boyfriend, now her husband.

"I was given two pills a week," Neufeld said, "but after I had a physical reaction, I stopped them. Others also had physical problems. But once they get over the reactions, I'm sure they perform better." CAPTION: Illustration, no caption