Does testosterone give trans women a sporting advantage? Yes, it does

Early last week, after the announcement that New Zealand’s Laurel Hubbard will become the first transgender athlete to compete at an Olympic Games when she represents the women’s weightlifting team for Tokyo 2020, Carole Hooven could easily have taken to social media and expressed her scepticism.

It’s not as if she isn’t qualified. A lecturer and co-director of undergraduate studies at the Department of Human Evolutionary Biology at Harvard University, Hooven, 55, not only earned her PhD at Harvard studying sex differences and testosterone, but has now written a book, Testosterone: The Story of the Hormone that Dominates and Divides Us, in which she devotes chapters to the matter of transgender athletes.

Yet Hooven knows better than to try and start nuanced debates online – especially about gender. Instead, she merely posted a link to the news story, and pointedly quoted the head of the New Zealand Olympic Committee: “We do know that there are many questions about fairness of transgender athletes competing in the Olympic Games but I would like to take this opportunity to remind us all that Laurel has met all of the required criteria.”

“Questions about fairness” is one way of putting it. The row about transgender competitors in women’s sports is notoriously flammable, and every time it hits the news, it tends to play out like this: news reports spark editorials, a Twitter dust-up starts, former Olympic athletes like Sharron Davies and Paula Radcliffe make their voices heard, Piers Morgan wades in, and by the end of the week, anybody with any real expertise is drowned out.

Hooven, with her 2,000 followers and thoughtful, level disposition, is among them, but her views on Hubbard – which she’s happy to discuss in the safer surroundings of an interview – are straightforward.

“I won’t comment on whether it’s fair,” she says, “but I can comment on whether trans women, who have experienced male puberty, would have an advantage, on average, in most sports over natal females: yes they do.”

The evidence, she says, is clear. Males and females don’t differ hugely in speed and strength before puberty, “but all that changes when the testes and ovaries come online and begin to produce sperm and eggs, along with different levels of sex hormones. That’s when males pull ahead. Reducing testosterone levels after puberty, as is the case in male-to-female transgender people who suppress their testosterone levels as part of hormone therapy [as Hubbard has], does not eliminate these advantages.”

Hubbard, 43, began her transition eight years ago, and is in full compliance with the International Olympic Committee’s (IOC) rules on transgender women. Athletes transitioning from male to female must declare their gender as female for a minimum of four years, demonstrate their testosterone levels are below 10 nanomoles for a minimum of 12 months, and maintain those levels throughout the duration of their eligibility to compete.

Some experts, such as IOC advisor Joanna Harper, an American medical physicist and amateur runner who transitioned from male to female, have argued that “after one year of hormone therapy, trans women no longer have a male-like advantage”.

But Hooven, and others, would argue that the advantage has already been gained. Among other things, male levels of testosterone during puberty, which are around 20-30 times that of female levels, help increase muscle mass, decrease fat mass, increase bone strength and height, and improve haemoglobin concentration, which allows for greater aerobic capacity.

“Depending on the sport,” Hooven says, “men outperform women by 10 to 50 per cent. For weightlifting in particular, the male advantage is about 30 per cent – not surprising, since males have, on average, about 30 to 40 per cent more muscle mass than females.”

She knows it is a subject fraught with ethical and legal issues, which is why she insists it is merely her job to communicate the relevant science.

“A fair solution to this complex scientific and ethical issue should be decided through open discussion and debate, in light of facts, and with sensitivity for the concerns of all parties, and without shaming those who hold views different from one’s own,” she says.

The latter part may be unlikely, but defending science against the online tumult is partly why Hooven chose to write a book about how testosterone is responsible for many distinct differences between the genders.

“I felt a lot of anxiety [in writing it] because it’s obviously controversial, but I’m somebody who doesn’t like a bully, and I like science, so I felt emboldened to stand up for what I believe in,” she says, speaking over Zoom from her home in Massachusetts.

A lot of people talking online about gender issues, she thinks, “are getting confused. Social justice issues are getting twisted into the science, and it’s driven by fundamental misunderstandings. It’s dangerous: if you hang your agendas on dubious science, you’re going to be in trouble if the facts turn out not to support your agenda.”

As Hooven outlines in her book, testosterone, despite being present in our blood in only minute quantities, is the hormone that drives not just the physical characteristics but also many of our behaviours.

She has always been fascinated by men and why they are the way they are, and diving deeper into the subject has even allowed her to understand the man closest to her – her husband, Alex Byrne, a British philosophy professor with whom she has a 12-year-old son – a little better.

“[Alex] is interesting because he is on the extreme end for males being unemotional, and sometimes I wonder what’s going on inside him,” Hooven says. “I probe and probe, but it seems just not to be in there, the same intense inner life that I have access to. For a long time I thought that was a defect.”

He could, I venture, just be British.

“I thought that! And I did some research, cross-culturally, on emotional expression, and you guys are at the bottom...”

A basic academic notion holds that emotional expression means vulnerability, which means weakness and showing fear, and that testosterone is why men and women differ in this regard. “That’s the theory,” Hooven says.

Once she looked into this, she stopped trying to change Byrne and accepted he was simply different.

“I do feel bad about how much time I spent pressuring him to be more like me, and once I stopped doing that I think it freed him to be more expressive. I didn’t realise that’s what I was doing, but he’s fine. And once I accepted that, things have improved immensely between us.”

Our testosterone levels vary all the time – throughout the day, even, and certainly throughout our lives – and Hooven cautions against the current rise in men taking testosterone supplements in middle age to quell effects of the so-called ‘andropause’ (sometimes termed the ‘male menopause’).

“It’s a huge market, because there’s so much money to be made, and I think that’s really overblown. If you get into the literature, it’s just not clear that increasing testosterone will solve the problems people think they have with age,” she says.

The andropause “is definitely a thing,” but she would say “eat right, exercise, stop smoking, don’t drink so much, and if you’re concerned, see a doctor” instead of seeking a testosterone supplement.

“What’s happening with the marketing now is that a 50 or 60-year-old guy who has depression or low energy or can’t get an erection, the first thing that is suspected is low testosterone, and I think you need to look at the whole individual and their health first.”

It is a measured response, and Hooven has written a thoroughly researched science book, but such is the febrile state of the world that given she has dared to offer scientific evidence for many of the key arguments in the gender debate, its publication could be met with controversy. Is she expecting a backlash?

“From the book? I am. I write about sensitive issues. I don’t use the ‘accepted’ language. I refuse to say ‘sex assigned at birth’ or ‘cisgender’” she says.

“So for those reasons I do expect backlash. But I hope it’s a resource, for trans people, gay people, everybody. To learn about themselves.”

Testosterone: The Story of the Hormone That Dominates and Divides Us (£16.99) is published by Octopus on July 8. To order, visit books.telegraph.co.uk or call 0844 871 1514. Come back tomorrow to read an extract from the book.