Semenya, who won the women's 800-meter title at last month's world championship in Berlin, has had a gender test, and the results given to track and field's ruling body were leaked to Australian newspapers.
Former IAAF medical commission chairman Arne Ljungqvist would not comment specifically on the Semenya case, but he cautioned that a person's gender is not always easy to define.
"There is no simple, single lab test that can tell if you are a man or a woman. It is not black and white," Ljungqvist told The Associated Press by phone Friday from Sweden. "A person who carries a legal certificate showing that he is a man or a women, then they are a man or a woman."
Semenya comes from a poor village in rural South Africa and first drew attention when she won the 800 title at the African junior championships. With her muscular build and deep voice, more questions were raised at the world championships.
The International Association of Athletics Federations confirmed that Semenya was undergoing a gender test on the day she won the gold medal in the 800 by a huge margin.
Australian newspapers reported that Semenya has no ovaries and has internal testes, which produce testosterone. The IAAF didn't confirm or deny the reports, saying it was reviewing the test results and would announce its findings in November.
"There are many, many other reasons why a woman looks male," Ljungqvist said. "Probably the most common has nothing to do with intersex: production of steroids from the adrenal gland. Most of the women you see who look like men are not intersexed. Some men have a very womanlike body shape."
Another key issue is whether an intersexed person can make use of the natural male hormones they may be producing.