It is difficult to determine exactly how much testosterone affects the body, but current knowledge suggests that it is not a definitive answer to the question.
When a man is injected with testosterone, society perceives it as a way to enhance performance. However, for men with high natural levels of this hormone, it can be a competitive advantage. For women, on the other hand, it is considered unfair according to some leading sports organizations.
Athletes such as Caster Semenya and Dutee Chand have struggled in recent years to compete as women because their testosterone levels are well above average. Organizations such as the International Association of Athletics Federations and the International Olympic Committee have imposed strict limits on the acceptable testosterone levels of these women, arguing that this creates an unfair advantage. Each new decision sparks heated debate.
When a man is injected with testosterone, society perceives it as a way to enhance performance. However, for men with high natural levels of this hormone, it can be a competitive advantage. For women, on the other hand, it is considered unfair according to some leading sports organizations.
Athletes such as Caster Semenya and Dutee Chand have struggled in recent years to compete as women because their testosterone levels are well above average. Organizations such as the International Association of Athletics Federations and the International Olympic Committee have imposed strict limits on the acceptable testosterone levels of these women, arguing that this creates an unfair advantage. Each new decision sparks heated debate.
Some researchers support the position of the IAAF and IOC, but many others believe that dividing by testosterone levels does not take into account the complexity of the scientific evidence. Despite much discussion, it has not yet been clearly defined what the science actually says about the effect of testosterone on women's athletic performance, and the reason for this is simple: there is not enough convincing evidence.
When it comes to the link between testosterone and athletic performance, it's difficult to draw clear conclusions because the human body is a complex system. What we do know is that among elite athletes, men tend to have a consistent 10-12% advantage over women. Many attribute this advantage solely to testosterone, but there are many other factors such as various hormones and social aspects that can also influence athletic performance. One way to study the effects of testosterone is to administer supplemental hormone and observe changes in performance.
A recent study showed that runners using testosterone cream increased their time to exhaustion, which is considered an indicator of athletic ability. This study was supported because it demonstrated how high levels of testosterone can provide a competitive advantage. However, such studies are not always relevant to the discussion of naturally produced hormones.
The administration of exogenous testosterone is actually doping. «We've always known that doping improves athletic performance. Although the molecule is the same, injecting testosterone does not equal naturally produced testosterone levels. Adding testosterone has a greater effect because the body is not used to it» — says Katrina Karkazis, a senior researcher at the Global Health Equity Partnership at Yale University.
If it's not possible to study testosterone supplementation in men, the natural levels of the hormone and their relationship to performance should be studied. Men have significantly higher levels of testosterone than most women, and it has traditionally been thought to be the main reason for their athletic success. «There are undoubtedly many factors that influence performance, and testosterone is just one of them. However, when looking at the factors that differentiate men from women in sport, most biologists agree that testosterone plays a key role» — states Joanna Harper, a medical physicist at Loughborough University who specializes in trans athletes.
If it's not possible to study testosterone supplementation in men, the natural levels of the hormone and their relationship to performance should be studied. Men have significantly higher levels of testosterone than most women, and it has traditionally been thought to be the main reason for their athletic success. «There are undoubtedly many factors that influence performance, and testosterone is just one of them. However, when looking at the factors that differentiate men from women in sport, most biologists agree that testosterone plays a key role» — states Joanna Harper, a medical physicist at Loughborough University who specializes in trans athletes.
This idea is based on the assumption that testosterone improves two main aspects: strength and aerobic capacity, which is the body's ability to deliver oxygen to the muscles. Testosterone is a powerful anabolic hormone that promotes significant increases in muscle mass and overall strength, especially in the upper body where there are more receptors for it. It also helps increase the number of red blood cells in the blood, which increases aerobic capacity.
Logically, testosterone should improve athletic performance. However, if it did, we might expect a clear link between testosterone levels and performance, but this is not observed.
If you look at professional male athletes, you cannot predict their performance based on testosterone levels. Testosterone levels in men range from 10 to 25 nanomoles per liter, and you can't say that a man with 25 nanomoles will necessarily outperform a man with 10. The same is true for women, which underscores that testosterone is not the only factor contributing to male athletic performance.
Logically, testosterone should improve athletic performance. However, if it did, we might expect a clear link between testosterone levels and performance, but this is not observed.
If you look at professional male athletes, you cannot predict their performance based on testosterone levels. Testosterone levels in men range from 10 to 25 nanomoles per liter, and you can't say that a man with 25 nanomoles will necessarily outperform a man with 10. The same is true for women, which underscores that testosterone is not the only factor contributing to male athletic performance.
It's unclear what other factors might influence this, but Holt notes that clues can be found by studying women with androgen receptor mutations. Androgens are a group of hormones, including testosterone and estrogen, that influence sex characteristics. Testosterone, for example, determines the sex organs of the developing fetus.
However, some people have mutations that cause the androgen receptors to become non-functional, and despite testosterone production, it has no effect. These people often develop as females without realizing their XY male chromosome set. In severe cases, they may have female genitals but internal testicles.
However, some people have mutations that cause the androgen receptors to become non-functional, and despite testosterone production, it has no effect. These people often develop as females without realizing their XY male chromosome set. In severe cases, they may have female genitals but internal testicles.
One study of professional triathletes found no link between testosterone levels and performance. Other studies of professional cyclists also found no correlation. Other work showed a negative correlation between testosterone levels and performance, and in adolescent artists there was no correlation at all. In some studies, results varied by strength type — endurance decreased with high testosterone levels, while maximal strength tended to increase.
As Karkazis notes, the current research model demonstrates extensive links between testosterone and athletic performance, but in practice only small correlations with certain measures of athleticism are found. These mixed results may explain why contradictory findings are found even in extensive reviews. Such reviews argue that there is insufficient evidence to establish a single upper limit for testosterone in women and that very specific limits need to be applied.
One reason for this uncertainty is the lack of quality research. Karkazis emphasizes that researchers have to form an idea of the role of testosterone based on data on men, women with sex developmental differences (so-called DSDs, including androgen receptor mutations) and people who have received exogenous testosterone. Peter Sonksen, a retired and former professor of endocrinology at St. Thomas' Hospital and King's College, London, has long written about the relatively minor effect of testosterone on athletic performance in women without androgen receptor mutations. However, he also notes that there is a dearth of robust scientific evidence regarding the role of the hormone in women with DSD.
However, these questions do not address the underlying problem: how to determine fairness in the rules of competition and who is eligible to compete. Some researchers, like Harper, believe that there should be a certain limit on testosterone levels for women; exceeding this threshold should mean that men should have to compete. However, many others believe this concept of fairness is flawed.
Eric Wilen, director of the Genetic Medicine Research Center at Children's National Hospital, argues that even if testosterone does give some women an advantage, they still have the right to compete with other women. He emphasizes that sports are based on ability, which is inherently unfair, pointing out that there are many factors that can give female athletes an advantage.
However, these questions do not address the underlying problem: how to determine fairness in the rules of competition and who is eligible to compete. Some researchers, like Harper, believe that there should be a certain limit on testosterone levels for women; exceeding this threshold should mean that men should have to compete. However, many others believe this concept of fairness is flawed.
Eric Wilen, director of the Genetic Medicine Research Center at Children's National Hospital, argues that even if testosterone does give some women an advantage, they still have the right to compete with other women. He emphasizes that sports are based on ability, which is inherently unfair, pointing out that there are many factors that can give female athletes an advantage.
Holt supports this view, saying that claiming the difference between men and women is solely in testosterone levels is an oversimplification. He adds that sociological factors must also be considered. For example, teenage girls participate in sports less often than boys and often face worse conditions. Male athletes generally receive more resources, which can also influence their success.
Furthermore, the idea that the natural changes in some women's bodies are unfair contrasts with the praise of male athletes with unique abilities. For example, Michael Phelps' muscles produce half as much lactic acid, which allows him to stay tired for long periods of time, and Finnish skier Eero Mäntyranta has an inherited mutation that increases the oxygen-carrying capacity of his red blood cells by 25-50%, similar to the effects of doping. These athletes become objects of admiration rather than condemnation.
Sports, by their very nature, already contain elements of injustice, and while some rules are necessary to deal with real violations, it seems odd to condemn women for the natural advantages we value in men. Simplifying the discussion to a single, albeit important, hormone ignores the more complex biological and sociological aspects, and Holt emphasizes that «we must celebrate these biological differences».
Furthermore, the idea that the natural changes in some women's bodies are unfair contrasts with the praise of male athletes with unique abilities. For example, Michael Phelps' muscles produce half as much lactic acid, which allows him to stay tired for long periods of time, and Finnish skier Eero Mäntyranta has an inherited mutation that increases the oxygen-carrying capacity of his red blood cells by 25-50%, similar to the effects of doping. These athletes become objects of admiration rather than condemnation.
Sports, by their very nature, already contain elements of injustice, and while some rules are necessary to deal with real violations, it seems odd to condemn women for the natural advantages we value in men. Simplifying the discussion to a single, albeit important, hormone ignores the more complex biological and sociological aspects, and Holt emphasizes that «we must celebrate these biological differences».