Realize that Caster Semenya is only competing because a former East German doping coach recognized the situation quickly and soon enough there was a 1:55 and a world championship, all in the same debut season. That coach knew where there was an advantage--he'd spent his career in the Soviet Bloc helping athletes raise their testosterone and now he had a natural one.
Legalize this and you'll have all Casters in the finals of every women's event, comprised largely, I am sure, of African athletes whose condition and gender were not reassigned one way or the other at birth, just as in the "women's" 800m, after Caster was allowed to compete without hormone restrictions, immediately there popped up a host of others, Niyonsaba, Ajok, and Wambui, all in the same event. The CT "transgender" 100m runners are a different issue, though one fraught with far more potential, because men with no testosterone deficiencies comprise close to half the population and you only need a few here and there to dominate all women's sports.