Testosterone, Sex, and Sport

Recent policies banning or limiting the participation of transgender and intersex women from the women's category of sport have called upon the science of testosterone to justify exclusion and define eligibility criteria. Scientific evidence supports a male advantage in sport, substantial sex differences in circulating testosterone, permanent effects on physiology from its long-term exposure, and a dose-dependent sporting advantage to its exogenous use. Yet, evidence connecting these findings has major gaps. Notably, no direct evidence shows that transgender and intersex women have a systematic sport advantage or that testosterone is the causal link. A brief review covers the relevant societal context, the science of testosterone, and the existing data used to support policies of exclusion. Key complexities, gaps in knowledge, and related ethical concerns all point to the need for more rigorous research.