[BBC] Caster Semenya has lost a landmark case against athletics' governing body meaning it will be allowed to restrict testosterone levels in female runners.The Court of Arbitration for Sport (Cas) rejected the South African's challenge against the IAAF's new rules.
But Cas said it had "serious concerns as to the future practical application" of the regulations.
Semenya, 28, had said the rules were "unfair" and that she wanted to "run naturally, the way I was born".
Now the Olympic, world and Commonwealth champion at 800m - and other athletes with differences of sexual development (DSD) - must either take medication in order to compete in track events from 400m to the mile, or change to another distance.
Cas found that the rules for athletes with DSD were discriminatory - but that the discrimination was "necessary, reasonable and proportionate" to protect "the integrity of female athletics".