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Scientists comment on differences in sexual development and boxers at the Olympic games.
Prof Jonathan Seckl OBE FRCPE FMedSci FRSE, Moncrieff-Arnott Professor of Molecular Medicine and Professor of Endocrinology, University of Edinburgh, said:
“These are general comments about the topic and not specific to either of the athletes as we don’t know any detail about their cases.
“The problem for the sports regulators is that simple chromosomal analysis (i.e. does the individual have a Y chromosome?) or simple measurements of testosterone (are levels elevated above the female reference range?) are far from sufficient to define female versus male.
“The classical example is ‘androgen insensitivity syndrome’. In the full blown syndrome, an XY individual has testes and plenty of testosterone in the blood, but this testosterone doesn’t work because the receptors for the hormone are genetically mutated and thus defective. Affected individuals are fully female (apart from having ectopic testes – meaning not in the usual location; they can be internal, in the groin, or apparent labia majora – and high testosterone levels) from conception. But there are milder forms of this syndrome which show reduced testosterone action but don’t abrogate this completely. Such individuals vary in appearance and capacity. The genetics and testosterone levels do NOT resolve whether the subject has a male or a female body.
“Then there are not so rare masculinising conditions in genetic females such as congenital adrenal hyperplasia. These patients have a genetic disorder which typically drives higher than normal testosterone levels but are XX females. In these subjects the testosterone levels are a fair guide to their “androgenisation”, but they vary with treatment and a host of other factors. Difficult to build rules here.
“And none of this takes account of the intracellular enzymes that activate or inactivate sex steroids inside the body’s cells. Some press reports have mentioned 5alpha-reductase type 2 deficiency. This rare syndrome is best reported in the Güevedoces in the Dominican Republic. Affected XY individuals are apparently female at birth because they can’t activate sufficient testosterone to the much more potent dihydrotestosterone to masculine in utero and thus appear female (the default gender in the absence of masculinising hormones). However, they have testes in what appear to be labia. At puberty, the testes produce much more testosterone sufficient to activate receptors and masculinise the child. Such subtleties are beyond the capacity of most regulatory bodies to accommodate.
“Overall, I suspect that this is all too difficult for the sports bodies to contemplate.”
Prof Alun Williams FBASES FTPS, Professor of Sport and Exercise Genomics, Manchester Metropolitan University Institute of Sport, said:
“The kinds of advantageous physical effects of elevated testosterone during normal male puberty include a larger skeleton meaning increased height and limb length, increased muscle mass and strength, increased size of organs such as the heart and lungs, and elevated blood haemoglobin concentration that helps deliver oxygen to muscles during exercise. Consequently, without separate male and female categories in sport, almost all success in sport would be achieved by males.
“However, when it comes to athletes with a DSD, there is almost zero direct evidence about their possible advantage over others who compete in the female category of sport. One can infer what kind of advantage some of those athletes might have, but there’s a lot of guesswork involved. That’s because there are many different types of DSD, and even within each type, the precise genetic cause someone has – which is often unique – will influence whether and to what extent their physical development relevant to sport has been affected. I wouldn’t be surprised if some athletes with some types of DSD have some advantages in sport, but the extent of that will vary, and some will probably have no advantage at all.
“Excluding some athletes with a DSD from the female category of sport without strong evidence they have an advantage is wrong in principle, and sport organisations are vulnerable to costly and embarrassing legal challenges if their testing procedures are not based on strong evidence.
“That’s why, if testing is adopted to identify whether any advantage exists, it should be as accurate as possible. Perfect accuracy is probably impossible, but robust testing would at least have to include genetics (in great detail, not just whether someone has a Y chromosome), hormones (testosterone and others), the sensitivity of the body to hormones like testosterone, and perhaps sport-related physical performance and anthropometric tests. In particular, assessing the sensitivity of the body to hormones like testosterone is highly questionable in ethical terms, because it involves invasive assessment of reproductive system characteristics like distribution of body hair, depth of voice, breast and clitoris size, and so on. There’s also the consequence of having to reveal life-changing personal information to athletes. For no purpose other than personal healthcare does such testing currently take place, so using it for sport purposes would be extraordinary.
“So those very significant ethical problems need to be weighed against any perceived benefit of using such tests. Those who do not consider athletes with DSDs to be women, or who prioritise the interests (including fairness and safety during competition) of the majority of female competitors over the interests of the minority of athletes with DSDs, tend to conclude that the problems with testing are acceptable. Others who consider athletes with DSDs brought up as girls/women to be women, and thus equate the interests of athletes with DSDs with those of all other women, tend to conclude that testing is not justified.”
Prof Ashley Grossman FMedSci, Emeritus Professor of Endocrinology, University of Oxford, said:
“We don’t know the details of the two athletes in question so we can’t make assumptions about what sex or gender tests they have or haven’t passed or failed in the past or at present.
“Some journalists are asking questions about DSD, or differences in sexual development, so here are some comments on what that is – though again I don’t know whether the athletes in question have this or not.
“Differences in sexual development (DSD) are extremely rare but are probably underdiagnosed and more common than we think. DSD is a whole class of differences – it doesn’t just mean one thing – and DSD is not a diagnosis in itself.
“The process of sexual development and differentiation is long and complex. We have the karyotype (which set of chromosomes we have), which determines the gonads that form during development, which then typically make internal sexual organs and then external sexual organs. External sexual organs usually develop father during puberty due to a rise in sex hormones, both male and female sex hormones. In the majority of people these changes are ‘consonant’, which means they proceed along a fairly constant trajectory, or line, such that the biological and hormonal changes are typically male or female. It should be emphasised that this development says nothing about gender identity or sexual orientation.
“But things go differently in some people, sometimes due to a genetic change, and they can have a ‘difference in sexual development’. If someone is diagnosed with a DSD they may be offered surgery or hormone treatment. Some people aren’t diagnosed until adulthood, but in many cases changes are seen in the neonatal period or childhood leading to investigation. Paediatric endocrinologists in particular are trained to deal sensitively with such patients to optimise their sense of themselves and their lives.
“When it comes to elite sport, it is up to the IOC and other bodies to make decisions as to how these things are dealt with. There may be an argument for not giving all athletes a baseline XX/XY sex chromosome test but only when there is a query to then test individuals, because there are all sorts of possibilities why someone might have certain sex chromosomes and an appearance that might be different.
“Not all DSD lead to higher (or lower) levels of hormones like testosterone – this depends on the specific condition.
“Adult male levels of testosterone do have an advantage when it comes to strength – testosterone levels in men and women can overlap, but even in women with polycystic ovarian syndrome (who may have slightly higher levels of testosterone than the average woman) the overlap is usually small. So a female with testosterone levels in the adult male range would likely have a strength advantage over other females. If someone has gone through male puberty they would – on average – have a strength advantage in female power sports, even if they then have low testosterone levels.
“But it’s not necessarily the case that having XY chromosomes in DSD always means someone goes through male puberty. Some individuals who have DSD and XY chromosomes would be given female hormones. Simply having the chromosomes doesn’t always mean people would have the expected testosterone levels.
“Some types of DSD would likely lead to advantages in sport, but it’s impossible to generalise. There is one type of DSD previously called testicular feminisation, now better called ‘complete or partial androgen insensitivity’ – where such individuals have male chromosomes (XY) but they lack the testosterone receptor and appear female as they don’t go through typical male puberty, so physically they are female. There is another type of DSD called 5-alpha reductase deficiency – these individuals would also have XY chromosomes but they usually would go through male puberty so would usually have higher levels of testosterone (some previous athletes with this condition have been required to take hormones to lower their testosterone levels to be eligible to compete, but this is a complex area).
“These are just two examples of DSD – there are many more, and we don’t know whether the athletes in question have these or indeed any other DSD.
“These issues are important for bodies like the IOC to address, in consultation with experts, but they are not straightforward.”
Declared interests
Prof Jonathan Seckl: “None.”
Prof Alun Williams: “Research funding received from the International Olympic Committee Medical and Scientific Research Fund, Independent Expert Witness in relevant cases at the Court of Arbitration for Sport (CAS).”
Prof Ashley Grossman: “No conflicts of interest.”