Throughout TESTED, we discuss a handful of “Differences of Sex Development,” or DSDs. This is the medical term used to describe a condition in which a person’s chromosomes, sex hormone balance, internal anatomy or external genitalia don’t develop as expected. (Different people use different terminology to describe people with variations in biology. For a guide on different terms like DSD, intersex, hyperandrogenic, etc read this sidebar.)
About 1.7 percent of people in the US are diagnosed with a DSD (for comparison, around 4 percent of US citizens are natural redheads and just 0.3 percent are identical twins). That percentage is probably similar globally, though it can be difficult to find exact numbers because many countries don’t collect statistics on DSD diagnoses.
A wide spectrum of characteristics, both physical and genetic, fall under the DSD umbrella. There is no single set of markers that applies to all people with these conditions. Similarly, there is no unified DSD identity – some people like the term “DSD”, while others find it pathologizing. Some resonate with the label “intersex”; others do not. And people with DSDs span the whole spectrum of gender, sexuality and gender expression. (You can see more about how we chose to navigate some of these questions of language and labels on the show here.) But the thing that unites the DSD athletes we spoke to and about in TESTED is an attempt by sports governing bodies to regulate their participation.
On the podcast, we didn’t have time or space to get into detail on some of these more technical definitions and diagnoses. But here you’ll find a more in-depth explanation of what criteria doctors (and in some cases, sports officials) use to categorize DSDs. What follows is a guide to some of the conditions that have been impacted by sex testing policies throughout modern Olympic history.
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Diagnosess previously regulated by the IOC
The International Olympic Committee (IOC),World Athletics (WA, formerly known as the International Amateur Athletic Federation, or IAAF) and other sports federations have been worried about gender verification ever since they started allowing women to compete. Initially — starting in the 1920’s — they tried to police womens’ bodies based on the appearance of their genitals. Some people with DSDs are born with differences in their external genitalia – for example, their erectile tissue, which everyone has in the form of a penis or clitoris, may develop into a size that falls between the average male and female presentation.
However, this method proved problematic. Not only was it invasive for the athletes, it was also not actually reliable as a method of finding women who might have DSDs. Not all people with DSDs have differences in their external anatomy – not to mention that genital configuration isn’t the best indicator of athletic performance. And doctors in some parts of the world perform surgeries on infants to “correct” genital ambiguity, a practice that continues despite being considered a human rights’ violation by the United Nations.
With the advent of chromosome and DNA testing in the 1960’s, the IOC and WA began looking at chromosomal differences instead. The Barr Body test, and later the PCR screen, focused on looking for a Y chromosome. But these tests also turned out to be unreliable. Not only were they poor predictors of athletic advantage (simply having a Y chromosome does not confer an automatic advantage in sports), they were also basically useless for determining someone’s sex or gender. Most of the women who were picked up using these methods did not know they had a DSD prior to being told by sports officials – an experience that often proved upsetting. Many of them were also not given further information about their condition after “failing” a test. They were simply told to fake an injury, and go home.
We don’t have data or records showing what specific DSDs the women who were eliminated from competition by these chromosome tests or visual examinations had. But here are a few DSDs that they may have had:
Congenital adrenal hyperplasia (CAH):
This is a genetic condition in which a person’s body doesn’t produce the enzymes they need to make specific hormones, including sex hormones. There is no specific arrangement of sex chromosomes associated with CAH. However, because of the balance of hormones they experience in the womb, people born with CAH may have genital differences. CAH can also cause a chronic salt deficiency, which can be dangerous or even fatal.
Ullrich-Turner syndrome (or Turner syndrome):
Turner syndrome occurs when a person has lost part or all of one X chromosome, resulting in 45,XO chromosomes. This usually stems from a difference in mitosis – some of one parents’ eggs or sperm cells form without a chromosome, or with a chromosome that is incomplete. The characteristics associated with Turner syndrome vary widely from person to person, but many people with the condition are short in stature, have low estrogen and may have fertility issues. Most are assigned female at birth.
XY mosaicism:
Also known as mosaic Turner syndrome – and accounting for around 12% of Turner syndrome cases – people with this condition are born with some cells that have XY chromosomes and other cells that have only X chromosomes. In most cases, this is because some of their Y chromosomes were lost during mitosis, although in rare cases, like Stella Walsh’s, XX and XY cells coexist in the person’s body. Many people with XY mosaicism are assigned male at birth, though some, including Foekje Dillema and Eva Klobukowska, are assigned female. People with XY mosaicism tend to be shorter than average and may be born with genital differences.
Klinefelter syndrome:
People with Klinefelter syndrome usually have 47,XXY chromosomes, though some individuals may have additional X chromosomes (48,XXXY or 49,XXXXY). They are typically assigned male at birth. Klinefelter often leads to taller-than-average height, decreased bone density and infertility. But because it does not usually cause many noticeable external differences, this DSD is rarely diagnosed before adulthood, and some experts estimate that up to two-thirds of cases are never diagnosed at all.
Complete androgen insensitivity syndrome:
Folks with complete androgen insensitivity have XY chromosomes and produce “typical” male amounts of testosterone. However, the androgen receptors in their cells are inactive, meaning their bodies don’t respond to masculinizing hormones like testosterone. They develop external sex characteristics such as a clitoris and breasts, and are usually raised as girls. Maria Patino was disqualified (and later reinstated) from competition for having complete androgen insensitivity.
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DSDs regulated by World Athletics’ 2023 policy
In the 1990’s the IOC and WA eventually ditched genital checks and chromosome tests, focusing instead on a specific subset of DSDs that elevate womens’ endogenous – or internally produced – testosterone levels. But this interplay is also complex. For one thing, these DSDs do not cause high testosterone in every individual; for another, most athletes’ testosterone levels fluctuate naturally over time.
What’s more, the scientific jury is still out on when (or to what degree) higher testosterone confers an athletic advantage. For example, people with partial androgen insensitivity might have high levels of testosterone circulating in their blood, but that doesn’t mean their body is actually able to use most of it. And even those who can process the testosterone, do not necessarily get a huge benefit from it. (We cover this at length on the podcast!) Here are the DSDs that World Athletics currently regulates, as of its most recent 2023 regulations.
5α-reductase type 2 deficiency:
This DSD is caused by a recessive gene on a somatic, or non-sex, chromosome. People with 5α-reductase type 2 deficiency usually have XY sex chromosomes, and are often born with genital differences because their bodies don’t produce very much of a specific type of testosterone called DHT.
17β-hydroxysteroid dehydrogenase type 3 deficiency:
This is a rare form of congenital adrenal hyperplasia (see above). People with 17β-hydroxysteroid dehydrogenase type 3 deficiency have XY chromosomes, but lack an enzyme that helps them synthesize testosterone. As a result, they may be born with “typical” female external characteristics, like a clitoris and vagina, along with internal testicular streaks or undescended testes.
Partial androgen insensitivity syndrome (PAIS):
Here’s an area where World Athletic’s current guidelines get especially tricky. Similar to complete androgen insensitivity (CAIS), PAIS means that a person’s body is not very responsive to testosterone. But unlike CAIS, people with PAIS still react to testosterone a little bit – just not as much as the average person. Because androgen insensitivity is a spectrum, the line between “partial” and “complete” insensitivity is fuzzy and difficult to pin down. It’s unclear from the regulations as written what amount of testosterone, or ability to process it, would qualify an athlete for regulation in the current rules.
Ovotesticular DSDs:
Ovotesticular DSDs cover a range of differences in a person’s gonads. People with these conditions are born with some combination of testicular and ovarian tissue. This may result from the translocation of a gene called SRY, which usually occurs on the Y chromosome, to an X chromosome. Sometimes infants with ovotesticular DSD are born with genital differences, but sometimes they have no external indicators.
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Other conditions that cause high endogenous testosterone that are not currently regulated by World Athletics rules
Testosterone is a complicated molecule that plays many nuanced roles in an athlete’s body. Despite this, the current World Athletics guidelines assert that testosterone is the primary reason that male athletes perform better than female athletes. For that reason, the organization has set a hard limit for female DSD athletes with the conditions listed above at 2.5 nmol/L of testosterone (between 0.5-2.4 nmol/L is “average” for women). If a “relevant athlete” (an athlete who falls under these rules) has a natural testosterone level above this range, she must lower it artificially to keep competing. The “normal” range for men, meanwhile, is considered 10-35 nmol/L – although some men have higher and lower natural concentrations.
It’s worth noting that World Athletics and other governing bodies do not impose an upper limit on male athletes’ endogenous testosterone, no matter how much higher it is than their competition. Some women also have natural testosterone levels above the WA limit, but are not required to artificially lower them if they don’t have one of the specifically listed DSDs. Here are a couple of conditions that can cause high testosterone and are not regulated under the current guidelines.
Hyperthyroidism:
Hyperthyroidism occurs when the thyroid – an endocrine gland located at the base of the throat – goes into overdrive. It can lead to elevated testosterone levels in both men and women, as well as increased metabolism, weight loss and anxiety. When Alberto Salazar, an Olympic runner and former coach of the Nike Oregon Project, was banned from coaching at the collegiate or professional level, one of the (many) sketchy things he allegedly did was make his athletes go on thyroid medication they didn’t need in order to boost their performances.
Polycystic ovarian syndrome (PCOS):
Polycystic ovarian syndrome (or PCOS) affects about one in 10 people with ovaries. It occurs when numerous tiny cysts develop in someone’s ovarian tissue. Folks with PCOS frequently have irregular or missing menstrual cycles and higher-than-average testosterone levels, and there is some evidence they are overrepresented in sports at the elite level. PCOS isn’t usually considered a DSD in medical circles, although it can push a woman’s testosterone levels above 2.5 nmol/L.
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Thanks to Hans Lindahl for consultation and editing on this piece.