Caster Semenya, a South African athlete who has won gold medals in the 800 meters race, has lost a landmark appeal against the International Association of Athletics Federations (IAAF)’s ruling that requires female athletes to have their testosterone levels regulated. That policy requires that all athletes with a difference in sex development (DSD) would have to reduce their blood testosterone levels to below 5 nmol/L for at least six months, and maintain those levels continuously while they compete, if they want to participate in international middle distance races.