Expert: Science won’t resolve debates about trans athletes

In a Q&A, endocrinologist Bradley Anawalt explains the "two essential disagreements" about equal access to sports competitions for transgender females. 


Dr. Bradley Anawalt is an endocrinologist and professor of medicine at the University of Washington School of Medicine. He is a member the NCAA Committee on Competitive Safeguards and Medical Aspects of Sports and a consultant to the U.S. Anti-Doping Agency Therapeutic Use Committee. This conversation from April 2023 was edited for clarity and length.

Q: What's the essential disagreement about allowing transgender and intersex women to compete with cisgender women in athletic competition?

bradley anawalt
"No policy or accommodation will leave all competing athletes or all members of the general public with a consensus of fairness about hormone therapies that might confer a competitive advantage," Dr. Brad Anawalt said.

Anawalt: There are two essential disagreements: one based on science and one based on social justice. The social justice issue is tension over fairness. One group argues that we should allow everybody equal access to participate in sports based on the gender they self-identify with. The second group says that people born with XY sex [male] chromosomes and who have exposure to testosterone as a developing fetus, infant and during puberty have an unfair biological advantage if they participate in sports as females.

In the scientific disagreement, many argue that there are important biological differences for a person who has grown up with exposure to testosterone and has an XY or other chromosome constellation consistent with being male at birth. Others say that difference doesn’t exist in transgender women if you suppress testosterone down to very low levels for at least a year.

The social justice question will never get a satisfactory answer based on science. I say that definitively because when a transgender woman participates as a female in a competitive sport and that person wins a medal or earns a scholarship, and a cisgender woman finishes barely out of contention for the award or the scholarship, the cis person might feel that they were displaced by a transgender woman based on an unfair advantage. Conversely, many will argue that it is unfair and unjust to exclude a trans woman from participating in sports as a woman.

Q: So, is science helping to address this issue at all?

Anawalt: We have relatively little firm scientific data to determine whether there is a biological advantage for the person who is born with XY chromosomes consistent with being assigned male at birth and exposed to testosterone.

Science might help address sport-specific questions. For instance, well-done research might determine that there is no competitive advantage in certain sports.   Maybe we should allow competitors in those sports to choose based not on their assignment of sex at birth, but on what gender they affiliate with.

I think that at the very highest levels in these sports, where scholarships are given out and there is a lot of money or public acclaim at stake, I think science is not going to provide enough facts to make it clear what's the right thing to do. There will be questions about the fairness of including and excluding individuals.

Barbara Ehardt, a former Idaho State Representative and athlete, speaks
Barbara Ehardt, a former Idaho state representative and athlete, speaks at a 2022 rally to advocate for restrictions on transgender females and "keep women's sports female."   

Q: Is it accurate to say males are generally stronger and faster than females in competitive sports?

Anawalt: After going through puberty, yes, collectively, males as a group will be stronger and faster than females as a group. The biggest distinction occurs after puberty: A male athlete at the highest level will typically be stronger and faster than a female at the highest level.

Q: Is it reasonable to assume that an intersex or trans female athlete would have a competitive advantage after puberty?

Anawalt: This is the critical question. When a male goes through puberty, things happen that potentially give a competitive advantage. The male begins to develop greater muscle mass, so in sports that rely on strength, size or speed, a male who has gone through puberty — including a rise in blood testosterone concentrations to levels typical of men — will typically perform better than a male who has not gone through puberty.

In puberty, your hands and feet get bigger, too. So if you're playing basketball and you can palm the ball, that's a competitive advantage.  But in a sport like ping pong that requires quickness but typically doesn’t emphasize strength, there might not be a significant difference between men and women.

In the controversy about trans female athletes participating as females in sports, an important consideration is whether the athlete has gone through complete puberty. Some transgender females go all the way through puberty as a male. Then they begin gender-affirming hormone therapy in which their testosterone is suppressed to a very low level, and they’re typically given estrogen therapy to raise blood estrogen concentrations to levels typical of women who have normal menstruation. The scientific data we have indicates that the muscle mass in a typical trans woman who went through puberty remains higher than the muscle mass of a typical cis female for at least one to three years.

We don't have studies with large numbers of trans individuals, and we don't have studies that extend beyond one to three years. Most rules governing participation of trans females as female athletes stipulate one year of testosterone suppression. But some changes brought about by puberty, like height and hand size, can't be reversed by suppressing testosterone, and could confer a permanent competitive advantage in sports where height or hand size is a good thing, like basketball and volleyball.

picture of Quinn #5, the first openly transgender athlete to win Olympic gold
Gold medalist Quinn #5, second from top left, of Canada's soccer team celebrates after becoming the first openly transgender athlete to win Olympic gold, in August 2021 in Japan. 

Q: It sounds like completing puberty is an important distinction.  Have many trans female athletes not completed puberty?

Anawalt: Today, a number of physicians and patients agree that we should start hormonal therapy before an individual completes puberty.  There has been a movement in the last decade to identify people who self-identify as a gender different than the gender they were assigned at birth before they begin puberty, or during early puberty.  Shortly after the onset of puberty, many clinical experts prescribe hormone therapy that basically stops the person’s production of sex steroid hormones, thereby stopping pubertal development.  After a period ranging from six months to two years, the trans person is then offered gender-affirming hormones, for instance, estrogen therapy for a trans woman.

Q: At that point, would the prospective unfair advantages of height and strength be interrupted, and their influence greatly reduced?

Anawalt: The prospective advantages of strength would be greatly or completely reduced.   There would need to be much larger, long-term studies to determine whether typical competitive advantages in strength are eliminated and whether potential competitive advantages related to height, hand size or foot size would reduce or eliminated.

Q: The World Athletics Organization is supporting a policy that would not allow trans athletes to compete in women's elite races if they'd gone through any stage of male puberty. Does it seem like athletics organizations are making reasonable accommodations to maintain fair competition while acknowledging the advantages conferred by puberty?  Or has that made the disagreement stickier?

Anawalt: I think it's gotten stickier than ever. This is that social justice issue where science is just not going to satisfy everybody on this. I worry that scientific facts will be used to bludgeon each other and that we won't come to a consensus because our feelings are so heightened.

Q: In organized sports competitions, the principle of fairness seems paramount. Do you think it’s possible to make an accommodation or a policy that leaves all competing athletes with a sense of fairness?

Anawalt: It's a critical question. The short answer is no. Even if some day, years or decades from now, we figure out all of the science of puberty’s influence on athletic advantage, there will still be doubts about fairness based on other differences between individuals who are born with male genitalia and XY sex chromosomes and individuals born with female genitalia and XX sex chromosomes.

No policy or accommodation will leave all competing athletes or all members of the general public with a consensus of fairness about hormone therapies that might confer a competitive advantage.

Q: Does it make sense to you to have an open category of competition where any athlete can compete?

Anawalt: Yes, there’s a broad range of options that I think should be open for discussion. You could have an open category that's not gender- or sex-specific. You could create categories that relate to the level of competition. So if we're talking about kids and teenagers in elementary school and club sports after the age of puberty, you wouldn’t focus on hormone concentrations and so forth. Instead, you’d allow the individuals to self-assign gender.

You could have different policies or options for college athletics, the Olympics and professional sports. For transgender athletes, you could make distinctions based on when somebody initiated their hormonal, gender-affirming therapy. There might be sport-specific considerations; right now, we're trying to give one answer for everything, and you can't come up with a single, clean, simple answer that's going to work for every circumstance.

Written by Brian Donohue - 206-543-7856,

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