South African runner Caster Semenya on Wednesday lost her court challenge against IAAF rules forcing female athletes to regulate their testosterone levels, but judges voiced concern with the application of the "discriminatory" regulations.

Semenya, a double Olympic champion, was fighting measures imposed by the International Association of Athletics Federations (IAAF) that compel "hyperandrogenic" athletes -- or those with "differences of sexual development" (DSD) -- to lower their testosterone levels if they wish to compete as women.