Following the recent media coverage of Caster Semenya competing at the Rio Olympics 2016, we have republished an abridged version of Harriet Nerva’s essay on disorders of sexual development, which won the Society for Endocrinology Undergraduate Essay Prize in 2010. You can read the full version here.

Gender verification and sport are two terms which when put together provide a bang louder than any starting pistol. In August 2009, Caster Semenya an 18 year old South African female athlete won the 800m sprint in the World Championship in Athletics in a world-record time. Her muscular build and fast time fuelled rumours of hermaphroditism and levels of testosterone three times that of ‘normal’. She was ordered to take a gender verification test. The worldwide controversy that followed has forced athletic organisations to create new guidelines for intersexed athletes, also known as those with a disorder of sexual differentiation (DSD). These are still being decided as this essay is written.

So are you female or male? The answer may seem simple enough – except that is for the 1.7% of the population who are born intersexed, and, for any young budding intersexed athlete out there, the consequences may be far reaching.

Introduced in 1936, and used to catch male imposters in female sporting events, compulsory gender testing of female athletes was abolished in 1992, with organisations retaining the right to test anyone thought of as ‘suspicious’. Males and females have traditionally been separated in elite sport because of the competitive advantage that men are argued to possess. The advantage stems from biologically determined sex differences in physical characteristics such as height, body composition, muscle mass, endurance and cardiovascular capacity.

However gender testing was never meant to address the issue of intersexed athletes. There is no evidence that female athletes with DSDs have displayed any sport-relevant physical attributes which have not been seen in biologically normal female athletes. Why is Semenya being tested? The grounds for her testing and the test itself have not been clarified.

DSD or ‘intersex’ refers to the atypical appearance of the external genitalia at birth where they differ from the usual development of either sex and create difficulty in sex assignment. The DSDs can broadly be split into 3 groups. Firstly, disorders of chromosomal sex occur when there is nondisjunction of sex chromosomes during meiosis. Secondly in disorders of gonadal sex, chromosomal sex is normal but the differentiation of the gonads is abnormal.

Thirdly there are the disorders of phenotypic sex. Here the phenotypic sex is ambiguous or is completely in disagreement with chromosomal and gonadal sex. Female pseudohermaphrodites (virilised females) have a 46, XX karyotype and female gonads, but ambiguous or male external genetalia. Male pseuodohermaphrodites (undervirlised males) have a 46 XY karyotype and male gonads, but ambiguous or female external genetalia. A true hermaphrodite has both ovarian and testicular tissue, irrespective of karyotype. Internal genetalia may also be mixed and external genetalia may be male, female or ambiguous.

Methods of defining gender in sport have been notoriously controversial. In essence what gender verification tries to do is find a cut-off point between females and males. This is harder than it sounds – sex is not defined by one parameter, it is a complicated combination of many, but athletics bodies have broadly used chromosomal sex for differentiation. Do DSDs always result in competitive advantage and do they always affect chromosomal sex test results? What about all this testosterone rumoured to be flying around?

Whereas in men a testosterone dose-response relationship has been shown to exist in sport, in women this relationship has only been found in relation to ‘explosive performance’. This measurement of height and power output involves performing the lowering portion of a lift at normal speed while the lifting portion is performed as rapidly and forcefully as possible. The dose-response relationship found was weaker in women than in men. It has been argued that this is because of gender differences in skeletal muscle sensitivity to testosterone, but this has not been substantiated. Whether women show a dose response relationship across all sporting attributes (for example endurance) is unknown, possibly because there is a lack of data on the relationship between resting testosterone levels in elite competitors and neuromuscular performance. In 2006 Cardinal and Stone found that testosterone levels varied significantly in different athletic groups, with sprinters having the highest values for both men and women.

And what of Caster Semenya? If judged ineligible to compete as a woman, she would also be ineligible to compete as a man, and if she refuses to consent to treatment (and is not taking anabolic steroids), must she be allowed to compete as an intersexed athlete based in moral obligation of athletic organisations? Finally as these organisations move to open “centres of excellence” around the world that would be equipped to treat intersexed athletes with anything from hormone therapy to surgery (Handley, 2010), what is the role of endocrinologists? Torn between controlling athletic prowess and the best interest of the client, we have to ask how level the playing field can, and should, ever be.