What we know about trans athletes’ ability to play: Part 2

Some sports organizations like the NCAA have requirements for trans athletes. Supporters of the bans say the science is still evolving and that these organizations’ guidelines need to be re-examined.
5:34 | 05/12/21

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Transcript for What we know about trans athletes’ ability to play: Part 2
The debate roiling over trans athletes dates back to Renee Richards, the transgender tennis player who was banned from the 1977 women's U.S. Open. Game, Richards! Reporter: When she refused to take a sex chromosome test. When I became a woman, my body had been primed with estrogens for several years. And my musculature is estrogen supported. It's not male hormone, testosterone supported. So I have the muscle mass and the muscle power of a woman. Reporter: The New York state supreme court eventually recognized her as legally female, ruling that her civil rights had been violated. She was allowed to compete with women. She lost in the first round, but what the public conversation focused on was that, okay, it might be okay now, but the domination of trans girls is around the corner. That was 45 years ago. We're hearing the same rhetoric now, though no one can point to a competing trans athlete, though the science can show the data is not lining up with the claims about categorical dominance. Reporter: Over the decades, elite sporting organizations adapted guidelines to allow trans athletes to compete. But as the transgender community has become more visible, their rights have been pushed into the political arena. All of the major sanctioning bodies, including, for example, the international olympic committee, U.S. Cycling, the NCAA, all have had picies on the books for years that are inclusive. Reporter: Dr. Madeline deutsche heads transgender care at the university of California So give me the medical thinking that is reflected in the NCAA policy. The treatment involves a blocking of testosterone into the female range. When you do that, you cause blood cell counts to go down into the female range. You cause muscle mass to go down into the female range. And those really are two primary inputs into athletic performance. Reporter: But the lawyers in the Connecticut track case refuse to acknowledge the science behind these established rules. I'm sure you're aware that the NCAA has rules for transgender athlete inclusion, including one year of testosterone suppression, and then eligibility. Does that seem unacceptable to you? It is unacceptable. The science, and there are dozens of studies that confirm, even after one year of testosterone suppress ants, the physical advantages that men have are insurmountable. They still have larger lungs, larger hearts, bone density, structure. Reporter: But the bulk of scientific data does not support that argument. The scientific community and culture is generally lined up with the fact that transgender females are female. I don't think these things have any kind of significant impact when you think about the fact that blood values move into the female range, and that's been studied. Bone density goes down, muscle mass goes into the female range. These are the primary predictors. Reporter: But one group we spoke with believes the science is still evolving for those who transition after puberty. And some of the guidelines set out by national sporting bodies may need to be re-examined vr. Andrea Yearwood says she's been undergoing hormone therapy for several years now. I think there's this persistent notion that somehow you as a trans female have a biological advantage. Every athlete has an advantage to each other. If you have a certain diet, you might be better an another athlete. If you train seven days and they train three days out of the week, you might be better genetics have advantages. I feel everyone might have an advantage, it isn't just specific to me and who I am as a person. Reporter: The Connecticut lawsuit has since dismissed, but the adf says they plan to appeal on behalf of cisgendered athletes like Alana Smith, who's still competing and considering various college scholarships. What are your plans for track and field, and what's the dream? I want to go to a d-1 school to run track and possibly go pro. Are the coaches and scouts looking around? Yeah. Reporter: Andrea is finishing freshman year at North Carolina central university. But she says her running days are over. Were you offered a scholarship? No. No. Can you explain to me why you think that is? Uh -- hm. I guess maybe because -- I mean -- maybe because I am trans. Schools may not want all that negativity attached to their name, attached to their university. What closed that chapter in your life? Was that voluntary on your part? I think yes and no. All the negativity -- I didn't feel like going through that for another four years all over as much as I would like to say it didn't affect me or it wasn't that bad, I mean -- in all honesty, it did I guess get to me a little bit, more than I would have liked it to. Trans athletes should have the ability to do what they love in the body in which they know who they are.

This transcript has been automatically generated and may not be 100% accurate.

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