SII Focus 21st February 2019

Caster Semenya’s challenge to the DSD Regulations: It’s complicated…

The Court of Arbitration for Sport (CAS) began its hearings into a challenge to the International Association of Athletics Federation’s (IAAF) Eligibility Regulations for the Female Classification (Athletes with differences of sex development (DSD)) this week. The challenge was launched by South African 800m runner Caster Semenya in June last year, with the support of Athletics South Africa (ASA), who seek a ruling from the CAS that the DSD Regulations are unlawful.

In October last year, the IAAF agreed to delay the 1 November 2018 planned implementation of the DSD Regulations. ‘In exchange for Ms Semenya and the ASA agreeing to an expedited timetable, the IAAF has agreed not to enforce the Regulations against any athlete unless and until they are upheld in the CAS award, which is expected on or before 26 March 2019’, read an IAAF statement.

Semenya’s challenge to the DSD Regulations is multi-pronged. ‘Caster Semenya will file the legal challenge to ensure, safeguard and protect the rights of all women on the basis that the Regulations are irrational, unjustifiable, and in violation of the IAAF Constitution (based in Monaco), the Olympic Charter, the laws of Monaco, the laws of jurisdictions in which international competitions are held, and of universally recognised human rights’, read a statement from Norton Rose Fulbright, who will represent the South African at the CAS. The IAAF will be represented by Bird & Bird.

The Human Rights Special Procedures body of the United Nations (UN) has urged the IAAF to withdraw the Regulations; the IAAF has published a 2018 Endocrine Reviews Study underpinning the logic behind the DSD Regulations; a letter has been circulated to members of the American College of Sports Medicine (ACSM) asking for signatures in support of the Regulations; allegations about breaches of confidentiality have been made; and more. These issues will be discussed in the article below, and go some way to explaining its ambiguous title…

What are the DSD Regulations?

Athletics is split into male and female competition, based on the perception that males enjoy a performance advantage in certain sporting events due to differences in size, strength and power. The IAAF considers its female classification as a ‘protected category’. The DSD Regulations are designed as a final test as to whether an athlete should be allowed to compete in its female category, based on the IAAF’s view that testosterone is the main driver of differences in size, strength and power between males and females. 

Its contention is that elevated levels of testosterone provide some women with such a boost to their physiology that it would be unfair to let them compete against women who do not benefit from the same boost. The IAAF contends that the physiology of most DSD athletes includes male gonads (testes) that produce levels of circulating testosterone not in the normal female range (0.12 to 1.79 nmol/L in serum) but in the normal male range (7.7 to 29.4 nmol/L), producing (if the athlete is not androgen-insensitive) lean body mass and levels of circulating haemoglobin well above the normal female range and in the normal male range. The DSD Regulations (PDF below) are designed to regulate athletes with one of seven listed differences in sex development (DSDs) competing in international events run between 400m and one mile in the IAAF female category, if their testosterone levels are above 5nmol/L and have an ‘androgenising effect’ (i.e. if that testosterone is taken up by their androgen receptors and boosts their physiology).

The DSD Regulations only apply to women:

• That have one of seven DSD conditions outlined by the IAAF in Article 2.2 of the Regulations;
• with naturally occurring testosterone above 5 nmol/L that compete in the Restricted Events;
• That have sufficient androgen sensitivity for naturally occurring testosterone at levels above 5 nmol/L to have a ‘material androgenising effect’.

Females covered by the Regulations must:

• Be recognised by law as either female or intersex;
• must use hormonal contraceptives to reduce testosterone levels to below 5 nmol/L for six months prior to competing;
• must maintain naturally occurring testosterone at below 5 nmol/L.

If a female athlete covered by the DSD Regulations fails to take these steps, they will be ineligible to compete in the international Restricted Events, or to set world records. However, they would be eligible for all non-international events, male category events, or any ‘intersex’ events offered in the future.

Only the IAAF’s Medical Manager may initiate an investigation into an athlete under the Regulations ‘when acting in good faith and on reasonable grounds based on information derived from reliable sources’. The athlete must bear any cost of any treatment required to comply with the Regulations, and appeals may only be directed to the CAS.

Caster Semenya & the IAAF

Caster Semenya’s battle with the IAAF goes back to 2009, when she was 18. Gender tests were conducted on her after she won gold in the 800m at the Berlin 2009 IAAF World Championships. “She is a woman, but maybe not 100%”, Pierre Weiss, General Secretary of the IAAF, told media at the time. “We have to see if she has an advantage from her possibly being between two sexes compared to the others”.

In an attempt to introduce a more scientific method of doing this, the IAAF introduced its Hyperandrogenism Regulations (PDF below) in 2011. The Regulations sought to prevent females with testosterone levels in serum of above 10 nmol/L from competing in all female events.

On 27 July 2015, the CAS suspended the Hyperandrogenism Regulations ‘for no longer than two years’, after they were challenged by Indian sprinter Dutee Chand. The CAS Panel accepted the IAAF’s argument that testosterone was a key causative factor in Lean Body Mass (LBM), which offers a competitive advantage and that men have a 10-12% competitive advantage over women, justifying separation between the sexes in the interest of fair competition. 

Detail from the 2015 Chand ruling…

The CAS found that Chand had been unsuccessful in her challenge to the scientific basis of the Regulations, as it was satisfied that ‘there is a scientific basis in the use of testosterone as a market for the purposes of the Hyperandrogenism Regulations’. However, it also found that there was an ‘assumption’ within the Regulations that elevated testosterone plus virilisation resulted in the 10-12% competitive advantage that males have over females. It asked the IAAF to prove this assumption.

The evidence does not go so far as to equate, or correlate, the level of testosterone in females with a percentage increase in competitive advantage’, found the CAS Panel. ‘The evidence does not, for example, establish an advantage of the order of 12% rather than, say 1% or 3%. Once the degree of competitive advantage is established, the IAAF would then need to consider, if the degree of advantage were well below 12%, whether that justified excluding women with that advantage from the female category.’

The CAS Panel added that the Hyperandrogenism Regulations would be declared void unless the IAAF could provide evidence proving the actual degree of performance advantage enjoyed by hyperandrogenic females due to their higher testosterone levels. On 5 July 2017, the IAAF submitted evidence, however it was based on studies performed at the Daegu 2011 and Moscow 2013 IAAF World Championships, where significant doping is alleged to have taken place.

The IAAF’s evidence maintained that female athletes with elevated testosterone enjoyed an advantage of between 1.78% and 4.53% in five athletics disciplines, none of which were Chand’s. This was below the 10-12% performance advantage that males have over females, as outlined at the CAS. The authors re-submitted the Study (revised version here) after flaws were found in the data. 

In a February 2019 article published by the Asser International Sports Law Journal, it is alleged that the revised Study remains the bedrock to the DSD Regulations, despite many of the flaws not having been corrected. Researchers found that the times of athletes disqualified for doping had been included in the Study, as well as duplication of some athletes and times.

On 28 July 2017, at the agreement of both parties, the CAS extended the IAAF’s evidential deadline until the end of September 2017. On 29 September 2017, the IAAF submitted its DSD Regulations to the CAS, along with evidence in support of the new Regulations and the Hyperandrogenism Regulations. 

‘On 3 November 2017, the CAS Panel advised that it has reflected upon the evidence advanced by the IAAF, and determined that the IAAF’s further submission dated 29 September 2017 represented sufficient compliance with the Panel’s directive and sought to support the Hyperandrogenism Regulations to the extent set out in the evidence it had filed’, read a CAS statement. ‘However, the Panel has made no ruling at this stage on the sufficiency of that evidence’. On 26 April this year, the IAAF published the DSD Regulations, which will come into force on 1 November this year.

There was therefore still a question as to whether the IAAF complied with the CAS’s original requirements in the Chand case. The CAS had asked the IAAF to demonstrate the actual degree of performance advantage enjoyed by hyperandrogenic female athletes. The IAAF submitted the DSD Regulations and evidence in support of their basis, but the CAS outlined that it had not made a ruling on whether that evidence was sufficient.

Dutee Chand

Chand argued that the IAAF had not complied with the CAS as it had issued evidence in support of new Regulations that would not apply to her (she is a sprinter, and the DSD Regulations only apply in running events between 400m and one mile). ‘If the IAAF withdraws the Hyperandrogenism Regulations and/or replaces them with the proposed draft Regulations it has submitted [the DSD Regulations], then these proceedings will be terminated’, read a CAS statement.

At first glance, it appeared that the CAS allowed the IAAF to close a case brought by an athlete against Regulations it had suspended by promulgating new Regulations and supporting evidence. The IAAF clarified that it asked the CAS to retain jurisdiction over the case and issue a ruling on the merits of the DSD Regulations, but Chand did not want to participate any further and, as such, the CAS took the view that it could not continue with the case.

The 2018 Study

Circulating Testosterone as the Hormonal Basis of Sex Differences in Athletic Performance, a 2018 Study, was cited as the major supporting Study underpinning the DSD Regulations. It had not been published when the DSD Regulations were promulgated, and was published by Endocrine Reviews in October 2018. A copy is held by The Sports Integrity Initiative, and has recently been published by the IAAF. A PDF is below.

The IAAF considers the above Study as evidence of the degree of unfair performance advantage enjoyed by female athletes with elevated testosterone – the question that the Chand case had not conclusively resolved. More specifically, the IAAF said that it provided conclusive proof of the performance advantage enjoyed by athletes with one of the seven listed DSDs competing in events run between 400m and one mile in the IAAF female category, if their testosterone levels are above 5 mol/L and have an ‘androgenising effect’. 

In the Explanatory Notes to the DSD Regulations (PDF below), the IAAF states that ‘increasing testosterone levels in women from 0.9 nmol/L to just 7.3 nmol/L increases muscle mass by 4% and muscle strength by 12-26%, while increasing it to 5, 7, 10 and 19 nmol/L respectively increases circulating haemoglobin by 6.5%, 7.8%, 8.9% and 11% respectively. Taking all available knowledge and data into account, the experts estimate that the ergogenic advantage in having circulating testosterone in the normal male range rather than in the normal female range is greater than 9%.’

The source for this statement is the 2018 Study above. The claims regarding increases in muscle mass and strength appear to come from a 2014 Study performed on 62 post-menopausal women (mean age, 53) who had undergone a hysterectomy. ‘The women whose testosterone concentrations were increased to 7.3 mol/L achieved significant increases in muscle mass and strength, ranging from 4.4% for muscle (lean) mass to between 12% and 26% for measures of muscle strength (chest and leg press, loaded stair climb)’, reads the 2018 Study. ‘In this study the highest testosterone dose (weekly injections of 25 mg of testosterone enanthate) increased mean circulating testosterone from 0.9 nmol/L to 7.3 nmol/ L, which is equivalent to the circulating testosterone of boys in early to middle puberty. After 24 weeks of testosterone treatment, the increase in circulating testosterone concentrations led to significant increases in muscle size of 4.4% and in muscle strength of 12% to 26%. Given the limited testosterone dose (and concentration) as well as study duration, it is likely that these findings underestimate the magnitude of the impact that sex difference in circulating testosterone has on muscle mass and strength, and therefore on athletic performance.’

The 2018 Study references a number of studies in support of the proposition that DSD athletes benefit from increases in circulating testosterone that increases circulating haemoglobin, which in turn translates to an increase in oxygen transfer. The first is a 2017 Study examining women with Congenital Adrenal Hyperplasia (CAH), a condition in which the adrenal gland can produce more testosterone. The Study found that in women with CAH, erythropoiesis may be driven by androgens. The proposition is that as DSD athletes have higher levels of testosterone (an androgen), they benefit from increased erythropoiesis (production of oxygen-carrying red blood cells).

The second is a 2017 Study which sets out that women with CAH can require glucocorticoid replacement therapy, but exhibit widely varying levels of hormonal control. ‘The degree of poor control is associated with increasing levels of circulating testosterone ranging from normal female concentrations up to 36 nmol/L, and these levels correlate closely (r = 0.56) with levels of circulating hemoglobin’, reads the 2018 Study. ‘Interpolating from the dose-response regression, increases in circulating testosterone measured by LC-MS from 0.9 nmol/L to 5 nmol/L, 7 nmol/L, 10 nmol/L, and 19 nmol/L were associated with increases in circulating hemoglobin of 6.5%, 7.8%, 8.9%, and 11%, respectively, establishing a strong dose-response relationship’.

The third is a 1972 Study into the response to exercise following blood loss and re-infusion, which the 2018 Study uses to support the proposition that an 11% increase in circulating haemoglobin translates to a 10% difference in maximal oxygen transfer. The 2018 Study asserts that this ‘may account for virtually all the 12% sex difference in male and female circulating haemoglobin’, referencing a 2014 Study as the basis for the 12% difference.

Much of the research referenced in the 2018 Study involves comparing endogenous testosterone levels with differences in muscle mass and strength. An ‘important finding’ is mentioned from a 2008 Study involving administering testosterone to genetically-modified mice. This involved breeding androgen-resistant female mice, which were found to have the same muscle mass function as normal mice, whereas androgen-resistant male mice were found to have smaller and weaker muscle mass than normal mice. 

‘Although these experiments cannot be replicated in humans, their key insight is that the higher circulating testosterone in males is the determinant of the male’s greater muscle mass and function compared with females’, reads the 2018 Study. ‘Studies of elite female athletes further corroborate these findings’, it mentions, referencing two Studies. The first is the 2017 Study previously mentioned, which uses data from the Daegu 2011 and Moscow 2013 IAAF World Championships, where significant doping is alleged to have taken place. This is the same Study in which it was found that flaws in the data had not been corrected.

The second is a Swedish Study (PDF below) published by the British Journal of Sports Medicine (BJSM) in 2017, involving 106 Swedish women. It found that female athletes have higher serum concentrations of dehydroepiandrosterone, 5-androstene-3β, 17β-diol and etiocholanolone glucuronide and lower estrone levels compared to controls; and in female athletes, precursor androgens and metabolites positively correlate to lean mass and muscle performance. ‘We found no correlation between serum T [testosterone] and physical performance’, reads the Study. ‘We suggest that endogenous androgens are associated with a more anabolic body composition and enhanced physical performance in women athletes’.

When mentioning the 2018 Study in May last year, the IAAF also pointed towards other evidence in support of the DSD Regulations. “There’s another category of evidence”, said Jonathan Taylor of Bird & Bird, who drafted the DSD Regulations for the IAAF. “I cannot tell people about this because it identifies athletes. But what it is, is evidence from the field. And evidence from the field is overwhelming. The results are incredible. Absolutely unbelievable. And any court that sees them will not be in any doubt.”

The 2018 Study reproduces data from Richard Auchus, a former Professor of Pharmacology at the University of Michigan. This shows that the 800m times of a female athlete subject to the IAAF’s Hyperandrogenism Regulations slowed after the introduction of the Regulations at the end of 2009, then quickened by five seconds over two years after the Regulations were suspended. 

‘Among elite athletes with circulating testosterone in the male range due to DSDs, comparable findings of athletic performance reduced by an average of 5.7% when circulating testosterone was suppressed from the male range to <10 nmol/L’, States the 2018 Study, referencing a 2017 Opinion Paper by Stéphane Bermon. In this Paper (PDF below), Bermon mentions how the lowering of circulating testosterone affected the performance of DSD athletes. ‘Monitoring performances obtained from hyperandrogenic DSD female athletes before and after they had their T levels lowered within the normal female range is a valuable and unique source of information to study the effects of androgens on female athletic performance’, he writes, referencing the graph on the right. ‘In these individuals, reducing T level from the normal male range to the normal female range led to an average decrease of their best chronometric performance of 5.7% over a 2 year period’.

As the above paper and graph illustrates, the 5.7% decrease is based on analysis of the times of three female distance runners with a DSD condition, who had their serum testosterone levels reduced to what the IAAF considers to be the ‘normal’ female range. The IAAF has denied that all of the evidence for this 5.7% drop in performance is based on four young female athletes who had undescended testicles removed ahead of the London 2012 Olympics. But in issuing that denial, it has admitted that some of Bermon’s evidence was based on those four athletes.

Surgery was performed on four young athletes (18, 20, 20 and 21), who were told that a gonadectomy would be likely to lower their testosterone levels and allow them to compete in the IAAF’s female category. The IAAF denies that it was responsible for telling the athletes this. “It was their choice to have gonadectomies, and the rest of it was their choice because when you are 17 and are told you are intersex and have ambiguous genitalia, some people choose to have surgery”, said Taylor. There is nothing in the DSD Regulations, just as there was nothing in the Hyperandrogenism Regulations, that requires athletes to undergo surgery.

‘Although leaving male gonads in SDRD5A2 patients carries no health risk, each athlete was informed that gonadectomy would most likely decrease their performance level but allow them to continue elite sport in the female category’, reads a Study referencing their case. ‘We thus proposed a partial clitoridectomy with a bilateral gonadectomy, followed by a deferred feminizing vaginoplasty and estrogen replacement therapy, to which the 4 athletes agreed after informed consent on surgical and medical procedures. Sports authorities then allowed them to continue competing in the female category 1 year after gonadectomy.’

The four athletes were 46,XY DSD and as such, their main source of hormones (the testes) had been removed. Testosterone and oestrogen are produced by both XY males and XX females in the testicles and ovaries (and also in the adrenal glands). When the testicles are removed, as they were in the case of the four young athletes, XY athletes lose the major source of hormones that their physiology requires. 

Kristen Worley is a transitioned XY female athlete, and suffered health complications after undergoing the same procedure and being forced to reduce her testosterone levels. Worley’s TUE took ten months to grant, and permitted her testosterone levels of 0.5 nmol/L, inducing complete androgen deprivation. She experienced a non-natural and aggressive ageing process; complete muscle atrophy (i.e. failure of muscle development and recovery, making sport impossible); anaemia; a large drop in haematocrit levels and other effects such as loss of libido.

As such, it is questionable whether the claim that suppression of elevated testosterone was the sole reason for the 5.7% drop in performance if any of the four young athletes were included in Bermon’s analysis. They had undergone a traumatic experience and surgery, which may have also affected their times. Also, as their undescended testicles had been removed, it is understood that they would not have needed testosterone suppression, as their major source of testosterone had been removed. In any case, Bermon’s assertion of a 5.7 drop in performance appears to be based on analysis of three athletes, and could therefore represent an anomaly.

However, the 2018 Study builds on Bermon’s evidence. ‘When the IAAF hyperandrogenism rule was suspended in 2015, and so these elite athletes could train and compete with unsuppressed serum testosterone levels, their athletic performances increased by a similar amount’, it states. ‘Additionally, circulating hemoglobin levels in these untreated DSD athletes were comparable with male athletes or with female athletes doping with erythropoietin’, it continues, referencing Figure 7, pictured on the right, which shows mean haemoglobin concentrations (g/dL) of 12 elite athletes in four groups of 3 XY or XX middle-distance runners. The data was collected from the Athlete Biological Passport (ABP) programme operated under World Anti-Doping Agency (WADA) guidelines. Figure 7 states that data for each athlete involved a minimum of three blood samples which, in the 46,XY DSD group, involved collecting blood when the athlete was not undergoing suppression of hormones.

‘However, when circulating testosterone was suppressed to <10 nmol/L, the levels of circulating hemoglobin were 12% lower and again comparable with nondoped, non-DSD females, corresponding to the 12% magnitude of the sex difference in hemoglobin between men and women’, continues the 2018 Study, referencing a 2014 Study asserting that 12% haemoglobin difference. The Sports Integrity Initiative has asked the IAAF to clarify the reference for the above claim.


The human physiology doesn’t distinguish between endogenous (internally produced) or exogenous (external) testosterone, which is why it is effective as a doping substance. An athlete dosed with testosterone will show an improvement in performance, as their physiology has been boosted by steroid hormones not produced by their physiology. Their body has something new which it didn’t have before.

What is less certain is the effect that higher endogenously-produced testosterone has on sporting performance. An athlete with higher endogenous testosterone as a result of their physiology is not adding anything new to their body. High testosterone is their normal. They are not getting something new that they didn’t have before.

Increasing endogenous production of testosterone through diet, etc., would be almost impossible, and measuring results whilst discounting other variables could be problematic. Therefore, the only method of method that scientists have come up with is dosing people with testosterone and measuring the effects.

‘There is no known means of increasing endogenous testosterone in women to anything like the requisite degree to attempt to answer these questions’, reads the Study. ‘Hence, the only feasible design of such studies would be testosterone (or another androgen) administration to healthy young women […] We are currently performing a double-blind, randomized, placebo-controlled study of the effects of moderately increased testosterone concentration on physical performance and behavior in young healthy women ( no. NCT03210558). However, obtaining ethical approval to administer supraphysiological testosterone doses that maintain circulating testosterone in the male range for sufficiently prolonged periods, as well as the practical difficulties in recruitment, are likely to remain obstacles to definitive resolution of this question.’

It would be possible to measure the testosterone levels of female athletes with similar body mass and compare their times, without dosing anybody. If the athletes with higher testosterone levels showed faster times, then that could indicate that testosterone might be the reason that some female athletes perform better. Presumably, the scientists commissioned by the IAAF to produce the 2018 Study considered this idea and discounted it for good reasons.

The IAAF also asserts that there is no overlap between the level of testosterone in male and female athletes, arguing that the CAS rejected a 2014 paper asserting ‘complete overlap between the sexes’. This may be true, however a January 2019 paper (PDF below) indicates that there is some debate about whether all females with 46,XY DSD conditions covered by the Regulations have endogenous testosterone levels that fall within what it considers to be the ‘male range’. This includes women with CAH.

The androgen receptor question

It is understood that sensitivity of androgen receptors, which control the uptake of testosterone by the human physiology, differ between men and women, but also between individuals. ‘There is also anecdotal evidence that the dose-response curves may be left shifted so that testosterone has greater potency in women than in men at comparable doses and circulating levels’, admits the 2018 Study.

Also, as highlighted by the 2018 Study and most of its supporting evidence, women generally start with a lower baseline level of testosterone. This perhaps goes someway to explaining why testosterone is so effective as a doping substance for females. But according to an expert who is currently conducting research in this area, testosterone is only half the story.

‘The focus is now on the level of testosterone, which is easy to determine, but only half the truth’, wrote Dr. Dick Swaab of the Netherlands Institute for Neuroscience in an email. ‘In order to let testosterone work on muscles, bones brains etc., an androgen receptor and a whole molecular cascade that is stimulated by the receptor is needed. There are many variations (polymorphisms, SNPs [single‐nucleotide polymorphisms]) in the receptor and related molecules that determine the sensitivity of a cell to testosterone. A receptor complex that is more sensitive to testosterone can also be seen as ‘unfair’. A receptor complex that is less sensitive to testosterone needs more testosterone to function in a ‘normal way’. The sensitivity to testosterone is not easy to determine.

‘A second, more philosophical point. We have all millions of such small variations (SNPs) in our DNA. The variation was the driver of our evolution. Elite athletes are people that have an exceptional combination of such SNPs in their DNA to start with. Consequently, fair play does not exist. I realise that the consequences of both remarks are not easy to implement in elite sports.’

Testosterone is not the sole driver

The IAAF Study makes a point of refuting the suggestion that endogenous secretion of growth hormone (GH) results in differences in muscle mass and function between the male and female sexes. It references seven Studies showing that endogenous GH secretion in young women is twice as high as in young men. 

It adds that this doesn’t result in young women developing muscle mass and function above that of young men because oestrogen ‘inhibit[s] GH-dependent, hepatic IGF-1 [Insulin-like Growth Factor, an anabolic agent] production, the major pathway of GH action […] Finally, the evidence that endogenous GH plays no role in sex differences in muscle mass and function is supported by evidence for the most extensive interventional Study of GH treatment to non-GH-deficient adults, daily GH administration for 8 weeks to healthy recreational athletes produced only marginally significant improvement in exercise performance of men and none in women’, it reads, referencing a 2010 Study commissioned by WADA. ‘These findings are consistent with the speculation that HG (or IGF-1) may be an amplifier of testosterone effects and therefore be a consequence of the sex difference in circulating testosterone rather than its cause’.

That may be the case, but the major conclusion of that 2010 Study was that GH supplementation influenced body composition in men and increased sprint capacity in both men and women when administered alone and in combination with testosterone. In other words, GH did have an effect on women’s sprint capacity, which could be an advantage in athletic events. Also, if oestrogen acts as a blocker to the production of IGF-1 that one might expect from higher levels of GH in young women, then perhaps low oestrogen levels might also be considered a performance advantage in female athletes? Again, it is presumed that the scientists commissioned by the IAAF to produce the 2018 Study considered this, and discounted it for good reason.

Health concerns

The DSD Regulations seek to cover athletes with one of seven DSDs who wish to compete in international female competition. As the title of the Regulations suggest, this includes anyone with a ‘difference of sexual development’, or to use a more scientific term, anyone who falls into the 46,XY DSD category. According to a 2014 study, such disorders are rare in the general population (a frequency of less than 1 in 20,000), but more common in elite sport (1 in 421 female athletes), where people with genetic advantages (longer stride, greater height, bigger hands or feet) can excel. 

As previously mentioned, testosterone is produced by both males and females. It also plays a vital role in the human physiology, especially in the XY phenotype. This is because in the XY phenotype, androgens (such as testosterone) are understood to be the primary stimulus for protein cell synthesis. In the XX phenotype, the primary source for this function is understood to be growth hormone, produced in the liver. 

Protein cell synthesis is understood to help the body develop red blood cells, muscles and ligament tissue. In simple terms, it is understood that the XY phenotype requires between six and ten times the amount of testosterone than the XX phenotype to ensure that protein cell synthesis continues effectively – or in other words, to maintain health. 

As also previously mentioned, it is understood that in the XX phenotype, androgen receptors are more sensitive to the effects of testosterone. In the XY phenotype, it is understood that more circulating testosterone is required to produce the same effects. The DSD Regulations seek to limit testosterone levels in serum to below 5 nmol/L in XY athletes with a DSD.

As such, it has been argued that the DSD Regulations could have serious implications for the health of XY females they apply to. This is because the DSD Regulations lower the natural testosterone in the XY phenotype, which is their primary source for protein cell synthesis. Of course this is likely reduce an athlete’s performance, as the body’s ability to regenerate itself has been affected. 

The DSD Regulations recognise that there is likely to be an impact on athlete health. They explain that a physician conducting an initial clinical examination on an athlete under the DSD Regulations will explain ‘the potential consequences both for the athlete’s health and for her eligibility under the Regulations’. 

Footnote 13 of the Regulations clarifies that this is because ‘such conditions may have implications for the athlete’s health, and diagnosis can often help to improve the conditions, avoid metabolic disorders, and possibly reduce the risk of later cardiovascular events and gynaecological cancers’. Nowhere in the DSD Regulations, or in the Explanatory Notes, is there any mention of measures taken to monitor an athlete’s health after her natural testosterone levels are reduced to below 5 nmol/L.

The IAAF insists that its experts have taken the health implications into consideration in drafting the DSD Regulations. It also insists that its experts worked under great consideration in order to ensure that the health of athletes with one of the seven DSDs is not damaged by reducing their endogenous testosterone to below 5 nmol/L. It argues that DSD athletes who have not undergone a gonadectomy would be required to take a contraceptive pill, similar to that taken by XX women for birth control reasons.

However, as explained, the DSD Regulations deal with the XY phenotype. As such, the impact of taking such a pill on that phenotype are not fully understood. In a September 2018 letter to IAAF President Sebastian Coe, the Human Rights Special Procedures body of the United Nations (UN) outlined that medical harm can be caused by forcing XX women to lower their endogenous testosterone levels. ‘Hormonal treatment to lower testosterone levels has adverse side effects including: diuretic effects that cause excessive thirst, urination and electrolyte imbalances, disruption of carbohydrate metabolism (such as glucose intolerance or insulin resistance), headaches, fatigue, nausea, hot flashes and liver toxicity’ they wrote, citing scientific studies published in the British Medical Journal (BMJ).

The UN also highlighted the medical harm that a gonadectomy can cause. ‘These surgeries can cause irreversible harms to women, including compromising bone and muscle strength and risking chronic weakness, depression, sleep disturbance, poor libido, and adverse effects on lipid profile, diabetes, and fatigue’, states the letter, again citing the BMJ.

Support for the science

At the end of the 2018 Study, a Disclosure Summary outlines that all three authors have conducted work for the IAAF. David J. Handelsman is described as a medical and scientific consultant for the IAAF and to the Australian Sports Anti-Doping Authority (ASADA), a member of WADA’s Health, Medicine and Research Committee and of the International Olympic Committee’s (IOC) Working Group on hyperandrogenic female and transgender athletes.

Angelica L. Hirschberg is described as a medical and scientific consultant for the Swedish Olympic Committee and a member of both the IAAF and IOC Working Groups on hyperandrogenic female and transgender athletes. It mentions that she has received grant support from the IAAF for a study examining testosterone and physical performance in women.

Stéphane Bermon is described as a medical and scientific consultant for the IAAF and a member of both the IAAF and IOC Working Groups on hyperandrogenic female and transgender athletes. Bermon is also Director of the IAAF’s  Health and Science Department, and has conducted much of its research in this area, including the disputed 2017 Study based on data from the 2011 Daegu and 2013 Moscow IAAF World Championships.

It appears that the IAAF has sought support from the American College of Sport Medicine (ACSM) for the idea that testosterone is the main driver for the difference in sports performance between men and women. Jonathan Taylor, the drafter of the DSD Regulations for the IAAF and Stéphane Bermon were copied into an email to its members that contained the following attachment (PDF below). 

In an email, an ACSM spokesperson outlined that the above letter is ‘neither an official position of the American College of Sports Medicine nor was it broadly circulated among ACSM members as a corporate communication. The letter was drafted, reviewed and signed by those at the bottom of the letter as a representation of their individual, personal and professional opinions regarding the topic, not on behalf of or representing ACSM’s position. Like other nonprofit organisations, ACSM respects a member’s autonomy in pursuing and conducting their individual professional work. This, however, does not necessarily constitute ACSM’s support or agreement with its members’ activities, outcomes or opinions.’

Forget the science – what about human rights?

As mentioned above, Caster Semenya’s legal team have learnt from the Dutee Chand case and have not just challenged the scientific basis of the DSD Regulations. They also allege that they are a violation of the IAAF Constitution, the Olympic Charter, the laws of Monaco, the laws of jurisdictions where international competitions are held, and universal human rights.

In its letter to Sebastian Coe last year, the UN urged the IAAF to withdraw the DSD Regulations. In the letter (PDF below), three UN Special Rapporteurs for physical and mental health; torture; and discrimination against women highlight ‘serious concerns’ that the DSD Regulations:

• Contravene human rights standards and norms;
• do not present evidence justifying that they pursue a legitimate aim;
• are not reasonable and objective;
• do not demonstrate proportionality between their aim and effects.

The letter points out that although the Regulations state that they are not ‘intended as any kind of judgement on or questioning of the sex or the gender identity of any athlete’, their effect would be to exclude an athlete from the IAAF’s female category, which would ‘most likely be interpreted as a judgment or questioning of their sex or gender identity’. 

The letter also points out that amongst other legislation, the Regulations may contravene the following:

• Universal Declaration on Human Rights;
• International Covenant on Economic, Social and Cultural Rights;
• Convention on the Elimination of All Forms of Discrimination Against Women
• Covenant on Economic, Social and Cultural rights.

It also points out that informed consent is a fundamental feature of the right to health, and there are questions about whether the DSD Regulations offer athletes covered by them such consent. ‘Intersex persons are recognized […] as a group deserving special consideration regarding the protection of informed consent, due to elements of vulnerabilities stemming from economic, social and cultural circumstances which significantly overlap and exacerbate inequalities’, state the Rapporteurs.

As previously mentioned, the UN is also unequivocal about the health implications that the DSD Regulations could have. It outlines that athletes covered by the DSD Regulations have little choice but to undergo surgery if they wish to continue competing.

What’s good for the goose isn’t good for the gander

The DSD Regulations define people as being eligible for ‘male’ or ‘female’ international athletic categories. They are also only applicable in its female category. There is no upper testosterone limit applicable in male international competitions, whatever phenotype (XX or XY) is competing.

The IAAF argue that this is because its male category isn’t considered protected, whereas the female category is. The UN points out that the IAAF has not sought to apply similar Regulations to men, despite the obvious fact that natural physical and biological traits affect their sporting performance. The 2018 Study appears to argue that testosterone is the primary driver for differences between the physiologies of men and women. 

Under the DSD Regulations, athletes with a DSD must lower their natural testosterone levels to 5 nmol/L. However, XX females transitioning to become XX males and wishing to compete in the IAAF’s male category are permitted to apply for a therapeutic use exemption (TUE) to take their testosterone up to what sport considers to be the male level. 

‘Those who transition from female to male are eligible to compete in the male category without restriction’, reads an IOC document (PDF below) entitled ‘Consensus Meeting on Sex Reassignment and Hyperandrogenism’, published in November 2015. The IAAF doesn’t have Regulations in this area at the moment, but its Explanatory Notes on the DSD Regulations explain that it ‘is currently reviewing and updating those regulations in light of the evidence identified above and in light of the learnings from the IOC’s 2015 Consensus Meeting on Sex Reassignment and Hyperandrogenism, and expects to issue updated regulations on this topic in the coming months’.

The result of this is that in some cases, XX Males are beginning to outperform XY Males. One example is Chris Mosier, a US cyclist and triathlete, who has transitioned to XX Male and is competing successfully in high performance endurance male competitions. His success is understood to be partly due to the fact that as an XX athlete, he is still receiving the testosterone endogenously produced by his XX physiology, yet sport permits him a massive boost of exogenous testsosterone that his XX physiology doesn’t need. 

Athletes covered by the IAAF’s DSD Regulations are not afforded the same privilege. Perhaps the IAAF’s male category should also be protected from athletes whose unique physiologies allows them what might also be considered an unfair advantage from elevated testosterone.


There is no level playing field in sport. Some athletes are taller, have longer stride length, are heavier, have larger feet or hands – all of which might confer an advantage in certain events. This is what makes sport exciting. The IAAF recognises this anomaly in the Explanatory Notes to the DSD Regulations.

If height were deemed to confer an unfair advantage in a particular event, then it might become appropriate to introduce height classifications’, it muses in the Explanatory Notes. There aren’t many 5 foot (1.5 metre) high jumpers, hurdlers or pole vaulters in elite athletics. 

As such, one might argue that the high jump is unfair to shorter athletes. In the high jump, an IAAF event, it would be fairer to measure the difference between an athlete’s height and the height cleared by that athlete. But sport isn’t about fairness – it is about celebrating people who have refined their unique physiologies to excel in a particular event. 

That includes very tall people whose unique physiology makes it easier for them to jump over the tallest height. In 2017, scientists working on the Genetic Investigation of ANthropometric Traits (GIANT) Project found that 83 genetic variations can have an effect on human height. “The genes affected by these genetic variations modulate, among other things, bone and cartilage development and growth hormone production and activation”, Professor Guillaume Lettre, one of the chief scientists working on the Study from the University of Montreal in Canada, told the Daily Mirror. And height is just one example of the human physiology.

The DSD Regulations focus on one specific aspect of the genetic and hormonal advantages that make some people faster, quicker, more coordinated, more supple, and/or stronger than other people – testosterone. They argue that elevated testosterone in athletes with one of seven DSDs gives them such an unfair advantage in a narrow range of events that it is necessary to exclude them from female competition. 

The GIANT Project shows that other drivers, such as genetics, also have an effect on the advantage that one person has over another, even in these narrow range of events. But height isn’t a protected category in terms of IAAF events, unlike the IAAF’s female category.

In the Chand case, the IAAF was tasked with proving the assumption that elevated testosterone plus virilisation resulted in the 10-12% competitive advantage that it asserted males held over females. Rather than doing this, it submitted new Regulations that narrowed the scope to athletes with one of seven DSDs, if testosterone levels above 5 nmol/L had an ‘androgenising effect’ (i.e. if it was taken up by their androgen receptors and boosted their physiology) in female events run between 400m and one mile.

As illustrated above, scientists commissioned by the IAAF have spent a great deal of time collecting research proving a link between dosing people with testosterone and measuring increases in muscle mass, strength, circulating haemoglobin and oxygen transfer. It also has collected research which shows that if testosterone is suppressed, decreases in all of the above can occur.

It has evidence that in DSD athletes covered by the Regulations, testosterone suppression results in a decrease in performance. However, as mentioned, this evidence appears to rely on a small number of athletes, some of which were subject to major surgery. As such, whether the CAS can accept that a drop in performance proves that in athletes covered by the Regulations, endogenous testosterone at above 5 nmol/L provides them with such an unfair advantage that it is necessary to exclude them from female competition, remains to be seen.

Also, as mentioned above, human rights considerations highlighted by the UN also underpin Semenya’s challenge to the DSD Regulations. It is hard to avoid the conclusion that an athlete who refuses to acquiesce to the DSD Regulations and is prevented from competing in international female events would be stigmatised as being a man.

‘The IAAF is not classifying any DSD (Differences of Sexual Development) athlete as male’, read an IAAF response to a recent The Times article‘To the contrary, we accept their legal sex without question, and permit them to compete in the female category. However if a DSD athlete has testes and male levels of testosterone, they get the same increases in bone and muscle size and strength and increases in haemoglobin that a male gets when they go through puberty, which is what gives men such a performance advantage over women. Therefore, to preserve fair competition in the female category, it is necessary to require DSD athletes to reduce their testosterone down to female levels before they compete at international level.’

Unfortunately for the IAAF, the language used in the 2018 Study doesn’t help the perception that the DSD Regulations are discriminatory. ‘Sex classification in sports […] requires proof of eligibility to compete in the protected (female) category’, it reads. ‘This deceptively simple requirement for fairness is taken for granted by peer female competitors who regard participation by males, or athletes with physical features closely resembling males, as unfair’. This appears to suggest that if you look like a man, you shouldn’t be allowed to compete as a female.

‘In women, supraphysiological testosterone effects are known to produce virilization side effects that may be only slowly and partially, if at all, reversible’, it continues. This statement contains an assumption that athletes affected by a DSD would want to reverse the effects of their condition.

Jonathan Taylor, who drafted the DSD Regulations, was specific about the need for the DSD Regulations. “The distinction between men and women we have established are not because they have an Adam’s Apple, a beard, or a penis, but because they have testicles pumping out testosterone”, he told The Sports Integrity Initiative last year.

‘Sex differences in physical attributes such as muscle size and strength and circulating haemoglobin levels give male athletes an insurmountable competitive advantage over female athletes in sports where size, strength and power matter’, he later wrote in a response to an article written by The Sports Integrity Initiative. ‘These advantages (which translate, in athletics, to an average 10-12% performance difference across all disciplines) make competition between men and women as meaningless and unfair as an adult competing against a child or a heavyweight boxer competing against a flyweight. Only men would qualify for elite-level competition; the best female athlete would not come close to qualifying.’

This comment again raises the question about why, if this is the case, the IAAF is only introducing the DSD Regulations to cover events run between 400m and one mile, and not other events. Also, as illustrated by the GIANT Project and explained above, factors other than testosterone also influence muscle size, strength, and circulating haemoglobin levels. 

An argument often proffered in defence of the DSD Regulations is that in their absence, the IAAF will be forced to drop its female classification entirely, leading DSD athletes and transgender athletes to dominate the podiums. However, as explained, the DSD Regulations only cover athletes with one of seven DSDs in events run between 400m and one mile, and only if circulating testosterone at above 5 nmol/L has an ‘androgenising effect’ on the athlete’s physiology. 

Despite the fact that DSD conditions are more common amongst elite athletes, they are still rare. The sporting events covered by the regulations only involve races run between 400m and one mile. As such, the idea that if Semenya wins her case, the IAAF would abolish the female category leading DSD athletes and transgender athletes to dominate appears to be little more than a political scare tactic. 

The background to this argument is presented in a 2010 paper written by Ross Tucker and Malcolm Collins. ‘Gender categories exist for the very reason that performance differences between males and females require that two separate categories exist’, they write (PDF below). ‘If, for example, a height category for athletes below a certain height were created to facilitate participation by shorter individuals in the sport of basketball, then fairness of competition would require that athletes taller than this limit be compelled to participate in the higher competition, even though their height is “natural” and represents no intent to cheat. 

‘In much the same way, authorities must defend equality of competition in the female category when the equality is questioned as a result of a physiological factor that challenges the basis for the gender categories in the first place […] Attempting to maintain the separate gender classifications, but failing to appropriately manage where individuals with DSDs and potential performance advantages should compete would be analogous to having a system where weight classifications exist, but then waiving the weight limit for certain individuals who cannot reduce their weight enough to fit into the required category.’

An issue with this argument is that it appears to legitimise sport to create whatever categories it wishes without considering whether they are fair. To follow this logic, the IAAF could rule that because Kenyans are good at distance running, they must race in their own category and be prevented from competing in international events. In order to prove that this proposition is necessary and proportionate, the IAAF would have to show that the magnitude of advantage enjoyed by the Kenyans is so large, that allowing them to compete against other distance athletes would be unfair on those other athletes.

In the case of DSD athletes, the CAS will have to make a judgment on whether the IAAF has done this in the coming days. The IAAF has already indicated that it may consider the creation of an ‘intersex’ category in the future. Again, this could be viewed as a threat as to what action it might take if the Semenya case doesn’t go its way, as the creation of such a category would be likely to create significant human rights concerns.

As mentioned in the title, it’s complicated. If you have read the entire article above and all the cross references, well done. You also deserve a medal. Caster Semenya’s case and the Regulations that underpin it is one of the most complicated issues that The Sports Integrity Initiative has dealt with. It has been reported that the South African government has contributed R25 million (€1.57 million) towards the costs of the case, although Semenya has distanced herself from such reports.

Speed skater Claudia Pechstein took her case to the European Court of Human Rights (ECHR). Like Semenya, her case also took ten years, and resulted in very limited success. Given the financial backing that has apparently been thrown behind her, there is no reason why Semenya wouldn’t consider doing the same.

Semenya’s hearing is being held in private, and her legal team has accused the IAAF of breaching of the confidentiality provisions of the case by publishing a list of experts it intends to rely upon in proceedings at the CAS, in an attempt to influence public opinion. The Statement included links to works produced by the experts, including 2018 Study referenced in this article. The IAAF said that these were only designed to indicate areas of expertise for the individuals, rather than the evidence that would be used at the hearing.

As illustrated above, the IAAF has conducted a great deal of research in this area, and clearly believes that it is doing the right thing in order to protect its female category from athletes which it considers to hold an unfair advantage. Whether it has provided sufficient evidence to prove that in DSD athletes covered by the Regulations, testosterone provides such a significant advantage that it is necessary to exclude them from female competition, is for the CAS to decide.

The CAS will have an extremely difficult task on its hands and whatever it decides, there is likely to be a backlash. Whatever ruling is issued by the CAS before the end of March, this case is unlikely to be over yet.

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