The participation of transgender people in competitive sports, a traditionally sex-segregated institution, is a controversial issue, particularly the inclusion of transgender women and girls in women's sports.
Opponents argue that transgender women have an unfair advantage over, and may endanger, cisgender women in competitive sports due to sex differences in human physiology, and that these differences are not sufficiently reversed by transgender hormone therapies. Supporters of transgender athletes argue that medically prescribed puberty blockers and estrogen suppress testosterone levels and reduce the muscle mass of transgender women, reducing possible competitive advantages. Supporters also argue that sport, particularly youth sports, is also about belonging, well-being, and socialization of young people. The American Medical Association states that legislation barring trans women from women's sports harms the mental health of transgender people.
The controversy has caused debates regarding sex verification in sports. Since the mid-twentieth century, sports institutions have responded to the participation of transgender women and women suspected to be transgender, male, or intersex by adding eligibility requirements to women's sports variously determined by physical examination, sex chromosomes, and sex hormones. Proponents of such regulations regard them as necessary to ensure fair competition and women's safety. Opponents have criticized such regulations as unfounded, degrading, misogynistic, discriminatory against transgender and intersex women, disproportionately affecting women of color, and violating medical ethics and human rights.[excessive citations]