ESPN is reporting that Caster Semenya, a two-time Olympic champion runner, has lost her appeal against proposed rules to limit her testosterone levels.

The article explains:

The ruling means Semenya will have to begin medically reducing her testosterone levels within the next week if she wants to compete in the world championships in Doha, Qatar, in September.

The South African runner, who won gold in the 800 meters in 2012 and 2016, was challenging proposals brought by the sport’s governing body — the International Association of Athletics Federations (IAAF) — to enforce limits on testosterone levels of female athletes with differences in sexual development (DSDs).

The Court of Arbitration for Sport’s panel of three judges gave a complex verdict but ultimately rejected Semenya’s case in favour of the governing body’s desire to protect fair competition among female athletes.

The article continues:

In April 2018, the IAAF introduced new rules that meant female athletes with differences in sexual development like Semenya would have to bring their testosterone levels in line with those of other female athletes.

The IAAF argued it was preserving fair competition, but Semenya — aware that the rules would have a significant impact on her career — believed she was being discriminated against and took her case to CAS.

…Semenya could decide to undergo testosterone-reducing treatment in the next week to continue running the 800m, but her lawyers have previously argued she could be as much as seven seconds slower if she does and would likely lose her status as a dominant champion of the event.

She could also change her event and compete at a distance outside the limits imposed by the IAAF, a possibility that has moved closer since she won the 5,000 meters at the South African championships a week ago.

Other athletes will also be affected, among them the 2016 Olympic 800m silver medalist Francine Niyonsaba of Burundi.

I have no idea what the actual details of this case are. What I do know is that higher levels of testosterone increase muscle mass and give the athletes with those levels an advantage over athletes with lower levels. I think the IAAF made the right decision. We are already seeing male athletes who claim to be transitioning to women earning gold medals in high school sports. Whether Semenya’s testosterone levels are natural or not, they give her an unfair advantage over other female athletes with lower testosterone levels.