Testosterone limits and Caster Semenya

Should there be a limit on how much testosterone a woman can have?
12 May 2019


starting positions on an athletics running track


Ruby Osborn reports on the recent athletics ruling concerning Caster Semenya, who has been told to use drugs to reduce her testosterone levels, if she wishes to continue to compete internationally... 

Caster Semenya is a South African middle distance runner who won gold for the 800m at both 2012 and 2016 Olympic Games. She also has higher levels of testosterone than is typical for women. Now, new rules from the International Association of Athletics Federations (IAAF) will require her to artificially lower her testosterone to continue competing at these distances.

What is testosterone, and why do people care how much of it Semenya has?

Testosterone is a hormone that has a key role in the development of male reproductive tissues, like the testes, as well as secondary male sexual characteristics such as facial hair growth and increased muscle and bone mass. Women naturally produce testosterone too, just in lower amounts.

On average, women have a blood testosterone level between 0.12 and 1.79 nanomoles per litre (nmol/l). 0.12 nmol/l is the equivalent of dissolving 1 teaspoon of sugar in the water of 40 Olympic swimming pools. Men usually have testosterone between 7.7 and 29.4 nmol/l. But people can have testosterone levels outside these typical ranges.

Some women, such as Caster Semenya, have elevated levels of testosterone due to differences in sexual development, or DSDs, in which their bodies naturally develop in a way that is not typical for males or females.

Most of the time, people who have two X chromosomes develop as women and have ovaries, and people with an X and a Y chromosome develop as men and have testes, because the Y chromosome carries a gene which triggers a fetus to develop as a male. But this isn’t always the case.

There are various causes for a woman to have a DSD. She may be XX and have an overactive adrenal gland that produces excessive testosterone. She may be XX but be born with both ovarian and testicular tissue. She may be what is known as a mosaic, where some of the cells in her body are XX and some are XY.

Or she may be XY, but during fetal development her body didn’t properly react to signals to develop as a male, meaning she instead developed as a female.

This can be a complete lack of reaction to testosterone, or mutations in proteins with roles in male development.

Women who have higher testosterone can show increased muscle and bone mass, and also higher levels of haemoglobin, the molecule inside red blood cells that binds oxygen. This can give an advantage in sports requiring a lot of power, such as running.

The IAAF says this isn’t just an advantage, it’s an unfair advantage.

In 2011, they set a blood testosterone limit for female athletes in all events of 10nmol/l. If a female athlete’s level was naturally higher than that, she must take drugs to artificially lower it. Following an appeal by Indian sprinter Dutee Chand, in 2015 the Court of Arbitration for Sport ordered the IAAF to suspend these rules until they had better scientific evidence for the ban.

Research by the IAAF has since shown that elevated testosterone levels in women increases performance up to 4.5% in the 400m, 400m hurdles, 800m, hammer throw and pole vault.

In 2018, it announced new rules that will require that any female athlete who wants to run distances between 400m and 1 mile (1609m) must have a blood testosterone level lower than 5nmol/l.

These rules only apply to women with DSDs and not, for example, polycystic ovary syndrome, which can also increase testosterone levels. They also exclude women whose DSD is due to an overactive adrenal gland. And, if an XY woman has developed as female because her body doesn’t respond to testosterone, she won’t gain any performance advantage from her testosterone level, and so doesn’t need to alter it.

Sport is split into male and female events, but gender identity, chromosomes, legal status, and biological development do not always neatly overlap. The IAAF propose blood testosterone levels as the best way to determine who is allowed to compete against whom, as the male/female division in sport boils down to the physical advantages from testosterone.

But why do the regulations only apply to female athletes with DSDs, and not with polycystic ovaries? Why are athletes whose DSDs are due to overactive adrenal glands exempt?

Semenya appealed against these new regulations, but lost her appeal on 1st May 2019. The new rules for all distances from 400m to 1 mile came into effect on 8th May.

So how can reducing testosterone affect the body?

Taking drugs to reduce testosterone levels can lead to reduced haemoglobin, reduced strength and muscle mass, fatigue, mood swings, and an increased risk of osteoporosis - weakened bones that are more likely to break.

Is it right to ask an athlete to change a natural part of their body that makes them excel at their sport?

Elite athletes are usually biological outliers, which is what allows them to compete at such high levels in the first place, but most such differences are celebrated.

The American swimmer Michael Phelps has won at least four gold medals in every Olympic Games since 2004. Among his physical advantages are size 14 feet, hyperflexible ankles and an armspan 3 inches longer than his height would suggest, all of which help to propel him through the water. He also produces around half the normal amount of lactic acid - the chemical which builds up in muscles during exercise and causes them to tire.

The science isn’t there to alter any of these features, but would he be expected to if it were an option?

Semenya and other athletes in similar positions are being placed under these regulations because they don’t fit within the IAAF’s parameters of what a woman should be. And yet, by their own sex verification test, Semenya is a woman. So is it Semenya who should be forced to medically alter herself, or should the parameters change?

As for Semenya, on 3rd May at the Doha Diamond League meet, the last competition before the new rules kick in, she won the 800m in her third best ever time, and said she’s going to keep on running.


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