Annet Negesa had just finished training in Kampala, Uganda, in June 2012 when she received a call from a doctor from track and field’s world governing body. He told her that she would no longer be competing in the London Olympics because her testosterone levels were too high for competition.

“I went back into the house and started crying,” she recalled.

Negesa was 20 at the time and one of the top athletes in her country, a promising middle-distance runner who had set a national record for 800 meters earlier in the year at a meet in Hengelo, the Netherlands. She was a three-time national champion and took home a gold medal at the 2011 All-Africa Games. The Uganda Athletics Federation named her athlete of the year.

World Athletics, formerly the International Association of Athletics Federations, or I.A.A.F., track and field’s world governing body, did not catch Negesa using performance-enhancing drugs. Rather, she is an intersex athlete.

She identifies as female and was born with external female genitalia but also with internal male genitalia that produce levels of testosterone that men do. According to sports officials, that gave her an unfair advantage over most women in some events.