Caster Semenya is a South African middle-distance runner and winner of two Olympic gold medals. Semenya is classified as an athlete with differences in sex development (DSD), a disorder that naturally gives her higer levels of testoterone. Research commissioned by the International Association of Athletics Federations (IAAF) showed in 2017 that female athletes with elevated testosterone had "a competitive advantage", claiming that high testosterone was responsible for as much as 3% improvement in runners. As a result, the IAAF has ruled that all women with DSD, including Semenya cannot compete in women's races from 400m to 1 mile unless they undergo treatment to reduce their blood testosterone levels. Athletes will need to do this for at least six months to become eligible, then maintain that level continuously in and out of competition for future events to remain eligible. Three methods suggested by the governing body for affected athletes to reduce their blood testosterone is to take medication, a monthly injection, or have their testes surgically removed.