PUBERTY blues
New rules affecting transgender women athletes in elite swimming have sparked controversy. What do they have to do with the stages of puberty? And what does the science say?
Trans women athletes were effectively barred from international swimming competitions this month, when the sport’s world governing body, Fina, introduced one of the strictest rules for eligibility to compete in women’s events.
Its inclusion policy stated that people assigned male at birth may participate only if they have not experienced any part of male puberty beyond Tanner stage 2, or have transitioned before the age of 12, whichever is later. A separate open gender category will be created instead.
The ruling follows the success of Texan transgender swimmer Lia Thomas, who in March became the first trans swimmer to win a division-one National Collegiate Athletic Association swimming title, the peak of US college sport.
Thomas competed for the University of Pennsylvania men’s swim team from 2018 until 2020 before going through hormone therapy and joining the women’s college competition.
Her win sparked debate about eligibility and fairness, and a discussion around how going through male puberty may – or may not – affect the performance of transgender athletes taking female hormones.
Why is puberty in the limelight?
Puberty marks the start of the body’s physical developments towards adulthood, some of which are considered to enhance elite sporting performance.
The stages of puberty discussed since Fina released its policy relate to a five-stage scale defined by paediatrician James Tanner in 1969 (after 20 years of research). Stage 1 is pre-pubertal but it is stage 2, the beginning or earliest phase of puberty, that has come under the spotlight. In boys, their testes start to grow and produce the hormone testosterone.
Testosterone acts by binding to a specific protein, the androgen receptor in muscles, which triggers an increase in muscle growth, mass and strength.
It also increases bone density, endurance and levels of the oxygen-carrying protein haemoglobin, allowing more oxygen to circulate, and ‘‘largely account(s) for the sex differences in athletic performance’’, according to research published by the American National Library of Medicine in 2018.
The testosterone of those female at birth peaks between 20 and 25 years of age before declining gradually, but generally remains at less than 2 nanomoles a litre at all ages.
Men’s circulating testosterone levels are generally 7.7 to 29.4 nmol/L. The Fina policy requires athletes in women’s events to maintain their circulating testosterone below 2.5 nmol/L, though in the past a level of less than 5 has been deemed reasonable and, before that, less than 10 nmol/L.
Swimming is not the only sport to be reassessing eligibility. Also this month, cycling’s world body, Union Cycliste Internationale, announced it would tighten rules for transgender athletes.
It doubled the amount of time before a rider transitioning from male to female can compete and lowered the testosterone limit from 10 nmol/L for a year before competition to 2.5 nmol/L for a two-year period. And the International Rugby League has excluded transgender athletes from international competition, including this year’s Rugby League Women’s World Cup.
Quoted in The New York Times, Mayo Clinic doctor Michael Joyner, an expert in the physiology of male and female athletes, notes that, before puberty, girls grow faster than boys and have a competitive advantage.
But after puberty, ‘‘you see the divergence immediately as the testosterone surges into the boys. There are dramatic differences in performances’’.
‘‘There are social aspects to sport, but physiology and biology underpin it,’’ he says. ‘‘Testosterone is the 800-pound gorilla.’’
The records for elite adult male swimmers are on average between 10% and 12% faster than those of elite female swimmers, the Times reports.
There is no sex-based advantage for boys before puberty, according to research by an international team.
After the completion of puberty – the end of Tanner stage 5 – according to international research published in 2018, the sex difference in athletic performance emerges as testosterone concentrations rise and testes produce 30 times more testosterone than before puberty.
Increased testosterone ‘‘provides a major, ongoing, cumulative and durable physical advantage in sporting contests by creating larger and stronger bones, greater muscle mass and strength, and higher circulating haemoglobin as well as possible psychological (behavioural) differences’’, the authors say.
‘‘These render women, on average, unable to compete effectively against men in powerbased or endurance-based sports.’’
That male bodies produce 15to 20-fold greater testosterone after stage 5 puberty than children or women at any age appears to explain why Fina made testosterone levels and puberty status the basis of its policy. (Fina was advised by three expert committees: one scientific, one legal and human rights, and one of athletes.)
Is there any proof of an advantage for transgender women?
One of the most contentious aspects of the discussion is the question of how much advantage testosterone – and its impact on those who have been through male puberty – allows trans athletes, who use hormones to dramatically reduce the body’s receptivity to it.
Fina referred to, but didn’t source, scientific evidence reported by a group of independent experts, of ongoing male biological advantage as proof of the need to act decisively.
Olympic swimming champion Kieran Perkins, chief executive of the Australian Sports Commission, is among those who say there is no significant study into what advantage, or disadvantage, elite trans athletes may have against elite female athletes.
‘‘I read Fina talking about the
science has been proved. What proof? Everything that I have seen suggests that, actually, we’re not really sure yet..’’
The Institute for Health and Sport at Victoria University and Austin Health have just started a study that aims to address current research limitations and provide clear data for policies and guidelines.
But for now, there is no good data giving insight into the competitive advantage, or otherwise, of transgender women, says Associate Professor Ada Cheung, an endocrinologist at Austin Health and lead at Melbourne University’s Trans Health Research Group.
‘‘There is some data but it’s not definitive and it’s not goodquality research,’’ she says.
‘‘No-one’s arguing there’s no difference between males and females . . . what we don’t know is how do feminising hormones impact on sporting performance after someone’s been through gender transition.’’
When a person starts taking feminising hormones, research has shown that fat mass increases while muscle mass and strength drop and blood-count haemoglobin – the oxygen-carrying red blood cells – decreases to female levels, Cheung says.
‘‘But there’s only one research study that has followed trans women out to three years, that involved 19 trans women. They showed that, at three years [after starting female hormones], muscle mass and strength was still declining and had not yet plateaued,’’ she says. ‘‘There was no comparison, and in research we always want to compare with a control group.’’
Evidence indicates that transgender women using hormone therapies experience
significant reductions in not only testosterone levels, but muscle mass, muscle strength and haemoglobin levels within the first 12 months of therapies, says Dr Patrice Jones of Victoria University.
Having a larger stature and smaller muscles – as a result of feminising hormones – may even be a disadvantage, says Cheung, who likens it to having a fourwheel-drive with a hatchback engine: ‘‘They might have the stature but don’t have the gas to power it.’’
Lia Thomas’ time of 4 minutes and 33.24 seconds over 500 yards (457 metres) of freestyle was nearly two seconds faster than that of runner-up Emma Weyant, who won silver in the 400m individual medley at the Tokyo Olympics.
Cheung notes that Thomas’ time was still slower than last year’s NCAA winner, the pool record and the college record, and 15 to 20 seconds slower than the men’s field. ‘‘She’s definitely competing within the women’s range, and has been through hormone therapy for at least three years,’’ she says. ‘‘The science isn’t sure whether she should be there or not.’’
The New York Times notes that, when Thomas entered women’s races, she rose substantially in national rankings. For example, Thomas had ranked 65th in the men’s 500-yard freestyle but won the title as a female.
‘‘Lia Thomas is the manifestation of the scientific evidence,’’ Dr Ross Tucker, a sports physiologist who consults on world athletics, told the Times. ‘‘The reduction in testosterone did not remove her biological advantage.’’
Why do experts dispute the puberty-stage and age ruling?
Dr Michele O’Connell, paediatric endocrinologist at the Murdoch Children’s Research Institute, says the ‘‘suppression of puberty from Tanner stage 2 or before age 12 – whichever is later’’ ruling will be almost impossible to apply, in and of itself, and will bring no guarantee of added fairness because children’s bodies mature at different rates.
The ruling may also push children to make decisions that have long-term effects, including on their fertility, before they are ready, says O’Connell.
In boys, puberty can start anywhere between ages 9 and 14, O’Connell says (puberty in girls usually starts between the ages of 8 and 12). Athletes assigned male at birth who begin puberty early at 9 ‘‘would have quite a different state of development from someone who progresses to Tanner stage 2 at age 13’’, she says.
She says the cut-off point for timing of pubertal progression poses risks to children who, while they may know they are trans, may wish to preserve their fertility, which would require their body reaching a further stage of sexual maturity than it is at Tanner stage 2.
‘‘This is talked about in clinical circles,’’ she says. ‘‘In all the recommended guidelines [for gender-affirming care], they talk about fertility and discussing that you might want to preserve some fertility and keep your options open before you go down gender-affirming pathways.
‘‘At Tanner 2, you wouldn’t be able to do that. You’d have to make the decision, I’m going to be an elite sportsperson and turn off my puberty now, versus I’m going to wait a bit longer and collect some sperm.’’
[After puberty] ‘‘you see the divergence immediately as the testosterone surges into the boys. There are dramatic differences in performances’’. Michael Joyner Mayo Clinic doctor
AFina spokesperson has said the idea that the ruling would create a rush to transition among aspiring swimmers was wrong.
‘‘This is not saying that people are encouraged to transition by the age of 12. It’s what the scientists are saying, that if you transition after the start of puberty, you have an advantage, which is unfair,’’ Fina’s James Pearce told the Press Association on behalf of the organisation’s president, Husain Al-Musallam.
‘‘They’re not saying everyone should transition by age 11, that’s ridiculous. You can’t transition by that age in most countries and hopefully you wouldn’t be encouraged to. Basically, what they’re saying is it is not feasible for people who have transitioned to compete without having an advantage.’’
But the ruling does present a reason for possible urgency around intervention, says O’Connell, ‘‘and that is not based in good science, and not in a person’s best interest – it’s for the potential benefit of others who would be competing against them, rather than for the individual’s wellbeing’’.
In the meantime, the debate about the necessity of defining who can compete in women’s sport continues.
Addressing Fina before the vote on its new policy was passed, Australian Olympic champion Cate Campbell spoke for it on the grounds that ‘‘women, who have fought long and hard to be included and seen as equals in sport, can only do so because of the gender category distinction. To remove that distinction would be to the
detriment of female athletes everywhere’’.
Meanwhile, Lia Thomas told Sports Illustrated in March: ‘‘I just want to show trans kids and younger trans athletes that they’re not alone. They don’t have to choose between who they are and the sport they love.’’ –