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expert reaction to ruling on caster semenya appeal regarding athletes with differences of sex development and testosterone levels

Reactions to a ruling from the Court of Arbitration for Sport that athlete Caster Semenya must take testosterone lowering medication in order to compete.

Dr Kirsty Elliott-Sale, Associate Professor of Female Physiology and Head of the Musculoskeletal Physiology Research Group, Sport Health and Performance Enhancement (SHAPE) Research Centre, Nottingham Trent University, said:

“In my opinion, this ruling puts us on a slippery slope.  The reproductive hormones oestrogen, progesterone and testosterone are endogenous (naturally occurring) hormones in females and males.  In women, these hormones change across the life span, from puberty to the menopause.  Indeed these hormones are cyclical in nature (peaks and dips) in adult females and change over the course of the menstrual cycle (every 28 days).  They also increase during pregnancy and are reduced as a result of many hormonal contraceptive use.  If sport start to put limits on these naturally occurring hormones, where will it end, given the number of times in a female’s life that these hormones are ‘higher’ and ‘lower’?  Moreover limiting these hormones in the long term will impact upon female health, contraceptive choices, fertility and so on, which is in my opinion an unreasonable request of any sportswoman.”

Dr James Barrett, lead clinician of the Charing Cross Gender Identity Clinic, and Consultant Psychiatrist, said:

Is this a scientifically sound decision?

“As sound as possible given what little we know and the implications of what we know.

Is this ruling based on evidence?

“Based on what evidence exists yes.  But we need more.

Does this ruling clarify the situation for other athletes in future?

“This ruling will allow the authorities (e.g. IOC and IAAF) to come up with the best rules/guidelines possible based on what little we know and these rules must be ‘fluid’ so they can be modified as we learn more.  In this way these rules will also clarify the situation for other athletes and become more fair as time passes.

Does this have any implication for transgender athletes in elite sports?

“I believe they do as M-F transitioned athletes will only be eligible to compete if their testosterone levels are controlled.  Once again we need to iron out the roadmap for implementation.”

Dr Silvia Camporesi, Senior Lecturer in Bioethics & Society, Department of Global Health & Social Medicine, King’s College London, said:

“This is such a weird verdict.  CAS is rejecting the Semenya challenge on grounds that regulations are necessary for women with DSD but advising IAAF to defer their applications until they have more evidence about a concrete advantage because of “difficult of relying on concrete evidence”.  (However, IAAF has not really taken up this piece of advice as they have given 1 week to athletes to lower their testosterone levels!)

“What “difficulty of relying on concrete evidence” means is that there is not enough evidence to support the regulations, as demonstrated by myself with Franklin and Jonathan-Ospina Betancurt for British Journal of Sport Medicine1 and others.

“Basically CAS has ruled today that IAAF has demonstrated that regulations are necessary and proportionate even if discriminatory on the basis of a theoretical advantage derived by testosterone in a sufficient number of 46 XY DSD athletes in the 1500m and 1 mile events, but not on evidence of a concrete advantage because of problems in replicability and false positives with the evidence submitted by Bermon and Garnier and underlying the regulations.

“However, the question of whether testosterone confers an advantage does not settle the question of whether an advantage would be unfair.  I’ve been working on this topic for the past ten years and always made the point that more evidence would not settle the question of whether an advantage would be unfair2.

“The verdict today can only be understood in light of the Interim Arbitral Award in the Dutee Chand case in 2015.  By ruling in 2015 that IAAF would have to come up with more evidence about the advantage derived by testosterone CAS set up the case in a way to favour IAAF buying into the assumption that more evidence would settle the question of unfair advantage but it DOES NOT!

“In order to do so, the following question needs to be addressed by CAS:

“1. In what ways (if any) is testosterone dissimilar from other genetic and biological variations that confer a performance advantage?

“2. How should we treat alike cases?

“The first of these two questions shapes the kind of evidence that CAS should be requesting.  The second question depends on what answer is given to the first.  Depending on whether CAS adjudicates that testosterone is similar, or not, from other genetic and biological variations that confer a performance advantage, there is the question of what to do with alike cases.

“The verdict by CAS today is extremely problematic as it falls short of recognising that scientific and clinical knowledge themselves are value-laden, and that the answer to the question of whether testosterone confers an advantage cannot be found only in science or clinical evidence, as it is a question of fairness.”



Dr Sonja Erikainen, ethicist, Visiting Fellow in the Centre for Biomedicine, Self and Society, University of Edinburgh, said:

“The IAAF DSD regulations that CAS has decided to uphold are arbitrary, inconsistent and un-evidenced.  They apply only to female athletes with 46 XY DSD whose testosterone levels can fall within the male range, which means that only women who have XY chromosomes are affected.  Yet, there are many conditions in which a female athlete who has XX chromosomes might also have testosterone levels in the male range, but these women are (rightly) allowed to compete without medical intervention.  Targeting athletes with 46 XY DSD specifically is unjust and arbitrary.

“Additionally, as the CAS panel acknowledged, there is insufficient evidence to support the theoretical idea upon which the regulations are built; namely, that athletes with 46 XY DSD have a significant enough advantage due to their testosterone levels to justify excluding them from the female classification especially in events over the distance of 1500m to 1 mile, and the evidence that does exist has been widely criticised including on methodological grounds.  The CAS panel correctly noted that the IAAF DSD regulations are discriminatory, but upheld them nonetheless.  This is contradictory to the Olympic Charter which upholds the right of all athletes to participate in sport without discrimination of any kind.”

Prof Chris Cooper, Emeritus Professor of Biochemistry in the School of Sport, Rehabilitation and Exercise Sciences, University of Essex, said:

“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 IAAF’s original hyperandrogenism regulations1.

“In the Chand case, CAS ruled that discrimination based on requiring a defined level of plasma testosterone was permitted if “on the balance of probabilities the Regulations are a proportionate means of achieving the legitimate objective of ensuring fairness in athletics competition.”  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 opportunity to provide the CAS with scientific evidence about the quantitative relationship between enhanced testosterone levels and improved athletic performance in hyperandrogenic athletes.”  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 “consider deferring the application of the DSD Regulations to these events until more evidence is available.”

“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 “necessary, reasonable and proportionate means of achieving the IAAF’s aim of preserving the integrity of female athletics in the Restricted Events.”  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.

Is there a link to current regulations on transgender athletes and doping?

“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.

Prof Peter Sonksen, member of the Society for Endocrinology, Emeritus Professor at St Thomas’ Hospital and King’s College London, and Visiting Professor at the University of Southampton, said:

“The decision is marginally scientifically correct, and in my opinion wrong.  Although it is based on evidence, the interpretation of that evidence is subjective and liable to bias.  For example, who defines and decides what a material androgenising effect actually is?  The ruling does make matters clearer for women with disorders of sexual development in future but is a separate issue to transgender women in sport.”

Prof Julian Savulescu, Director of Uehiro Centre for Practical Ethics, University of Oxford, said:

“Reducing the testosterone levels of existing intersex female athletes is unfair and unjust.

“The term intersex covers a range of conditions.  While intersex athletes have raised levels of testosterone, its effect on individual performance is not clear.  Some disorders which cause intersex change the way the body responds to testosterone.  For example, in Androgen Insensitivity syndrome, the testosterone receptor may be functionless or it may be partly functional.  In the complete version of the disorder, although there are high levels of testosterone present, it has no effect.

“As we don’t know what effect testosterone has for these athletes, setting a maximum level is sketchy because we are largely guessing from physical appearance to what extent it is affecting the body.  It is not very scientific.  We simply don’t know how much advantage some intersex athletes are getting even from apparently high levels of testosterone.

“It is likely that many winners of Olympic medals and holders of world records in the women’s division will have had intersex conditions historically.  It is only recently we have become aware of the range of intersex conditions as science has progressed.

“These intersex women have been raised as women, treated as women, trained as women.  It is unfair to change the rules half way through their career and require them to take testosterone lowering interventions.

“It is a contradiction that doping is banned because it is unnatural, risky to health, and reduces solidarity.  But in these cases they want to force a group of women to take unnatural medications, with no medical requirement, in order to alter their natural endowments.  Elite sport is all about genetic outliers.  Cross country skier Eero Mantyranta won seven Olympic medals in the 1960s, including three golds.  He had a rare genetic mutation that means the body creates more blood cells.  The oxygen carrying capacity can be up to 50% more than average.  This is a huge genetic advantage for endurance events like cross-country skiing.  WADA say “the spirit of sport is the celebration of the human spirit, body and mind”, but in this case, the rules seek to limit and quash bodies that don’t fall into line with our expectations.

“It is true that the rules of sport are arbitrary.  What defines man and woman will always have borderline cases.  But it is imperative these individuals are not unfairly disadvantaged.  It is unfair to take away a person’s life and career because you choose to redefine the rules.

“CAS agreed that the rules are unfair, but found the unfairness justified: “The panel found that the DSD Regulations are discriminatory but the majority of the panel found that, on the basis of the evidence submitted by the parties, such discrimination is a necessary, reasonable and proportionate means of achieving the IAAF’s aim of preserving the integrity of female athletics in the restricted events.”  Yet there is another option: to implement the rules prospectively by allowing a ‘grandmother’ clause for existing athletes who identify and were raised as women.  Then testing for new athletes could take place early as soon as puberty is complete to identify athletes who would come under the DSD definition.  Affected athletes could make an informed choice about continuing to compete at the cost of being required to take testosterone lowering agents.  This would still deny them the opportunity of competing to their full potential, but it would at least prevent individuals from investing their lives in a sport they would either not want to or be able to compete in.

“Intersex conditions can restrict people’s life options.  In many cases, it is not possible to have a biologically related child or carry a pregnancy.  Unfortunately, it can still carry stigma and discrimination (indeed CAS agree this is an example of it).  One possible upside is an advantage in sports.  This should not be denied.

“Sport is based on natural inequality.  If this is of concern to the authorities, I have argued that physiological levels of doping should be allowed.  This would allow all women to use testosterone up to 5nmol/L, as can occur naturally in polycystic ovary syndrome and which the IAAF has considered an upper limit for women with intersex conditions.  This would also reduce or eliminate the advantage some intersex athletes hold.

“The rules of sports are arbitrary but they should not be unfair.  Changing the rules to exclude a group of people who signed up under the current rules is unfair.  A change for future generations of athletes would be less unfair, but I believe that it will make for a less interesting competition and will still disadvantage some women.

“There is no fairy tale ending to this story.  Someone will be a loser.  But that is always the case in sport.”

Prof Ieuan Hughes, Emeritus Professor of Paediatrics, University of Cambridge, said:

“The Court of Arbitration for Sport (CAS) has upheld the IAAF ruling of a cut-off level of 5nmol/L of blood testosterone below which female athletes can compete in races from 400m to 1 mile.  This relates specifically to female athletes with differences in sex development (DSD) and have XY chromosomes (male sex chromosomes). The ruling is based on the much publicised appeal against this androgen restriction by the elite athlete, Caster Semenya.  How is this fair?  Biological sex at birth is usually binary, male or female.  Furthermore, from puberty onwards, blood testosterone levels are bimodally distributed to the extent that levels in males are much higher than in females.  CAS in their ruling acknowledge that in the interests of competitive fairness, there should be a separate classification for female athletes, a binary divide between male and female.

“In cases of DSD of the type exemplified by Caster Semenya, testosterone levels are higher than in the non-DSD female and often reach well in to the adult male range.  We know for certain from scientific evidence that the well-known biological effects of increased androgens, like longstanding effects on muscle mass and skeletal development, will provide a competitive advantage in female athletes exposed to these androgens (including testosterone).  Sports physiologists have clear evidence of that phenomenon.  So reducing the level of testosterone in the XY DSD athlete ahead of competing is a reasonable and pragmatic approach to achieve a level playing field.  The medicines used work, are devoid of complications and the effects are reversible.

“The CAS recognises that this protocol is not a perfect solution and emphasises the importance of monitoring compliance and the need for further research to strengthen the evidence for androgen-induced competitive advantage in sufficient numbers of XY DSD athletes, a challenge in itself owing to the rarity of these conditions.  The caveats placed by the CAS panel are to be welcomed, as will be an ongoing debate amongst endocrinologists, sports physiologists and administrators to ensure there is a collective responsibility to see fair play for whoever is competing.”

Prof John Brewer, Professor of Applied Sports Science, and Deputy Vice Chancellor, Buckinghamshire New University, said:

“While this ruling is a sad outcome for Caster Semenya and other athletes with hyperandrogenism, I agree with the ruling.

“The ruling is not unexpected.  Testosterone is a growth hormone which is why it appears on WADA’s list of banned drugs, and we know that at high levels testosterone is performance enhancing.  In athletes with hyperandrogenism, testosterone is not at levels that would normally result in an anti-doping rule violation and ban, but it undoubtedly would still give a performance advantage because of its effects on muscle strength and power, and general growth and development.

“It is important to emphasise that at the elite level where the margins between success and failure are so small, high levels of testosterone can provide a distinct advantage in many sports.

“Clearly nobody wants to discriminate against any individual who wants to take part in sport, including the large number of females who have normal levels of testosterone for female athletes.  But without this ruling we would have been in a position where females with normal levels of testosterone would be at a performance disadvantage compared with those who have higher levels of testosterone.

“There is an interesting additional recommendation in the ruling from CAS around the practicalities of implementing the ruling – and I agree with CAS that implementation and enforcement will be difficult.  They have also questioned the potential for the performance enhancing impact of testosterone on endurance events as opposed to shorter events and field events, where strength and power are fundamental to performance.  However increasingly we see that speed and power are important for endurance athletes, who require sustained power throughout an endurance event, and often high levels of speed and power towards the finish in order to win.  Therefore on balance, I think that it is only right that this ruling is applied across all events.

“Overall, what this ruling means is that there is a greater chance of a level playing field on which all female athletes can compete – and that has to be welcomed.”

Declared interests

Dr James Barrett: “I’m working with the International Olympic Committee to do physiological tests on young trans women to see exactly what changes actually do happen on standard treatment for trans women.”

Dr Sonja Erikainen: “I am currently writing a book on the history of this topic, titled “gender verification and the making of the female body in sport” forthcoming with Routledge, which is based on my PhD research that concerned this area.  I declare no conflict of interest.”

Prof Chris Cooper: “I have a book on the topic:”

Prof Peter Sonksen: “No interests to declare.”

Prof Julian Savulescu: “No competing interests.”

Prof Ieuan Hughes: “Professor Hughes is a member of the IAAF Expert Panel on Evaluation of Women Athletes with Hyperandogenism.  He played no part in the formulation of the IAAF Hyperandrogenism Regulations.  Professor Hughes was an author of the Consensus Statement of Management of Intersex in which the concept of DSD was defined and a classification system was devised.”

Prof John Brewer: “None.”

None others received.

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