I was on holiday during the CAS ruling on the appeal of the CAS hyperandrogenism regulations, so my comments are a bit late. The comments of the other experts who contacted the Science Media Centre can be found at this link
My comments are reproduced below:
"In my personal opinion, the IAAF regulations have as good a scientific basis as they are going to get in the foreseeable future. HOWEVER, this does not mean that they are ethically ‘right’. That is a separate matter. We should focus on the ethics of what we want to encourage as participation in female sport, and not get hung up on criticising the fine details of science that is never going to be as conclusive as we would like.
Although they have not released their detailed reasoning, the CAS decision to disallow the Caster Semenya and Athletics South Africa appeals is not surprising given their previous opinion in the case of Dutee Chand. Chand appealed against the . In the Chand case, CAS ruled that discrimination based on requiring a defined level of plasma testosterone was permitted if “.” The Court did not have a fundamental issue with the discrimination itself. It just had to be scientifically justified. The IAAF were then given “.” The IAAF then brought forward new regulations based on scientific evidence claiming that there was a significant advantage in certain events, specifically 400m, 800m, 1500m and mile. So the new case hinged not on whether discrimination is justified, but instead how large were the benefits of increased (natural) endogenous testosterone in female athletes. This new IAAF data was based on comparing performance of elite athletes at these distances with their testosterone levels. The published correlational data partially support this decision at 400m and 800m, but are less clear for the mile and 1500m (although scientifically it is hard to see why benefit at 800m would not partially transfer into a benefit at 1500m). Hence the current CAS Panel suggestion that the IAAF “.”
By asking the IAAF to use science to determine quantitively the specific advantage raised testosterone levels bring in elite athletes, CAS are, in my opinion, asking science to do too much. Proving evidence at the level of a specific event for individual athletes is only possible if you are allowed to drop or increase these levels in a controlled manner and measure the change in performance. Some of this individual data may indeed be in the final CAS report (although likely in redacted form). However, even then, individual hyperandrogenic DSD athletes will likely respond differently to changes in their testosterone levels. So any percentage change in performance would not be readily transferable to other DSD athletes. In effect the request for the IAAF to respond to the Chand ruling for more science was doomed to provide some light, but also more confusion. It is likely that this is the reason for the verdict being majority, and not unanimous.
Testosterone increases during development are clearly the dominant, if not sole, reason why male athletes outperform female athletes. The science is reasonably clear that DSD athletes with raised tesosterone levels will have some performance benefit even if their body only partly responds to those increased levels. But other factors clearly contribute to performance. In this context it is worth noting that Caster Semenya won the London 2012 800m when the original IAAF DSD regulations requiring lowered tesosterone were in force; the regulations were lifted for the Rio Olympics and she then won by greater margin. Using the IAAF regulations to handicap athletes with DSDs will have an effect on performance, but will likely not prevent them competing at an elite level. It seems to me predominantly an ethical, not scientific, question whether such discrimination is a “” Asking science to work at the level of granularity requested by CAS of the IAAF is part of the problem not the solution. Instead athletes and the public need to decide if they are happy with the percentage of DSD athletes being significantly over-represented at the elite level, compared to their prevalence in the general population. Adopting the IAAF regulations would decrease this over-representation, but likely not eliminate it entirely. I think this is predominantly a societal question rather than a scientific one.
The IAAF testosterone regulations regarding DSD (differences in sexual development) need to be seen in the light of their (and the IOC’s) anti-doping and transgender regulations. This is NOT to say that females with DSD or male to female transgender athletes are cheating of course. But the science underpinning the possible performance benefits of their situation is related. And in many cases – perhaps surprisingly – the doping data is easier to access.
On doping regulations: there is good evidence that increasing exogenous testosterone levels (or taking artificial anabolic steroids) enhances sport performance. This effect is greater in females than males. It is (partially) reversible if anabolic steroids stop being taken. It is no surprise that anabolic steroids preferentially enhanced performance in female athletes in the former East Germany (where they were likely given to junior athletes). Nor that the Russians state doping system had some of its greatest ‘successes’ when giving anabolic steroids to female middle distance runners. Therefore doping is banned.
On transgender regulations: lowering plasma testosterone levels is the main goal of male to female transgender hormone therapy. Transgender women, who are transitioning or have transitioned from male to female, are treated with hormones (by choice) to lower their plasma testosterone levels to similar levels as required by the IOC regulations. This decreases their performance. Therefore they are allowed to compete in a female category after hormone therapy to lower their testosterone.
Nothing about elite sports performance is ever going to be amenable to scientific conclusions ‘beyond reasonable doubt’. This is because the fractional differences in competition at the highest level are so small and the population so difficult to study ethically and practically. In my opinion the current evidence is as good as we are going to get to show that both endogenous (natural) and exogenous (doped) testosterone levels enhance female sports performance. In the terms of the Court of Arbitration of Sport, I am personally “comfortably satisfied” that both exogenous and endogenous testosterone increases sports performance in elite female athletes. Of course a lot of other factors, genetic and environmental, also affect sports performance, but that is a separate story."