Where sports performance meets reproductive rights: hormonal contraception

Abstract

Rational

To discuss the use of hormonal contraception (HC) in elite women’s competitive sports from an anti-doping perspective because 1) it changes the natural female hormonal milieu; 2) is used to manipulate the menstrual cycle with performance enhancement intent; 3) even though lowering endogenous testosterone levels, some HCs contain testosterone-like androgenic compounds with potential performance-enhancing effects.

Results

A complex interaction between rapidly advancing sports-relevant biomedical scientific discoveries, societal changes concerning sex and gender, and a zero-tolerance anti-doping ideology, leads to contentious results, jeopardizing the premises defining and protecting contemporary elite sport in general and that of women in particular.

Discussion and conclusions

This is in part because of the two out of three criteria for inclusion on the World Anti-Doping Agency’s List of forbidden substances and methods: i) actual or potential for performance enhancement, ii) actual or potential for health risk, and iii) counter to the Spirit of Sport concept. These criteria would suffice for the inclusion of HC on the List, especially in their androgenic form. The fact that they are not is good for women’s reproductive rights but also illustrates the arbitrariness of the administration of WADA’s Prohibited List of substances and methods in elite sports.

Keywords:

• Anabolic steroids
• sex hormones
• contraception
• sex
• gender
• sport
• doping

1. Introduction

As many as half of elite women athletes are estimated to use hormonal contraceptives (HC), with the most popular being the oral contraceptive pill (Burrows & Peters, 2007; Martin et al., 2018). The benefits from a sports performance point of view for people who menstruate are potentially multiple: most significantly, the prevention of unwanted pregnancies, while control over the timing of menstruation and minimizing pre-menstrual symptoms and painful periods are also important benefits that may enable women athletes to train and compete more optimally (Sulak et al., 2002). As such, hormonal contraception could be classified as performance-enhancing, or at least performance-restoring, in the sense that it can minimize the potential performance-impeding aspects of menstruating. Yet, hormonal contraception is widely accepted as a legitimate form of medication, including by the World Anti-Doping Agency (WADA), which does not prohibit its use in elite women’s sports. In this regard, it offers a useful case study for considering when and how a substance comes to be classified as illegitimately performance-enhancing (or not), particularly when that substance is bound up with questions of reproductive rights and bodily autonomy.

In 1999, the Olympic movement together with state government representatives decided to found WADA. Today, WADA is the global policymaking and harmonizing body for anti-doping efforts in international sports. In what follows, I first review WADA’s Prohibited List, with attention to the criteria that give WADA considerable latitude in how it determines banned substances. I then briefly review sex hormones with emphasis on female sex hormones and their manipulation with HC. Specific attention is given to so-called androgenic HC, with its potential relevance for sports performance. I then discuss WADA’s stance on the use of sex hormones, and by female athletes in particular, in keeping with the extant scientific knowledge about sex hormones. My argument’s objective is to highlight how a complex interaction between rapidly advancing sports-relevant biomedical scientific discoveries, societal changes concerning gender issues, and a zero-tolerance anti-doping ideology, leads to contentious results, which jeopardize the premises defining and protecting contemporary elite sport in general and for women in particular. I end by arguing that this is partly due to the criteria for inclusion on WADA’s Prohibited List. Strictly applying WADA’s criteria would be sufficient reason for the inclusion of HC, especially in its androgenic forms. The fact that this is not the case is yet another illustration of the arbitrariness of the administration of WADA’s List of prohibited substances and methods in elite sports.

2. The Prohibited List

WADA maintains a Prohibited List of substances and methods, a process led by WADA’s Prohibited List expert group (WADA, 2022). The reasoning for the inclusion of substances on the List is not made public but is seemingly based on three criteria laid out in WADA’s main reference document, the Code (WADA, 2021). A substance must meet at least two to be included: 1) potential or actual enhancement of performance; 2) potential or actual health risk; 3) counter to the Spirit of Sport of which the last sentence reads ‘Doping is fundamentally contrary to the Spirit of Sport’¹ (for complete wording of the three criteria see: (WADA, 2021)). The use of ‘potential’ in criteria 1 and 2, the use of all-inclusive language in the Prohibited List document referring for example to substances or methods still in pre-clinical research or yet to be discovered by science, and the ambiguous definition of the Spirit of Sport (Geeraets, 2018;; Heuberger et al., 2022; Loland & McNamee, 2019) provide WADA nearly unlimited leeway in determining which substances and methods are prohibited. In contrast to the prevailing rhetoric the inclusion of substances on the List lacks solid anchoring in scientific evidence (Heuberger et al., 2022). Rigorously applying the three criteria rule to placebos I concluded that even these could be added to the steadily lengthening Prohibited List (Kayser, 2020).

The Prohibited List is organized into three sections (WADA, 2022). One for substances and methods prohibited at all times, one for those only in competition, and one concerning particular sports. Sub-section S1 concerns anabolic agents which are prohibited at all times. It lists 76 agents, in two sub-sections, anabolic androgenic steroids, and other anabolic agents. The rationale, even though not made public, is presumably their actual (or, for some, potential) androgenic effects, similar to those of testosterone (also on the Prohibited List). Use of one (or more) of these substances 1) can enhance performance; 2) can induce side effects; 3) would run counter to the WADA Code’s Spirit of Sport (WADA, 2021).

Much recent discussion on the relationship between androgens and performance in women’s sports has focused on the place of transgender women and women with naturally high testosterone (Cocchetti et al., 2020; Krane et al., 2022). I instead focus on another aspect of this theme, namely the voluntary use of hormonal contraception (HC) by menstruating women participating in elite competitive sports. From a purely technical perspective, HC could potentially meet the criteria for being on the WADA prohibited list. I identified three reasons for this: firstly, HC artificially changes a woman’s hormonal milieu; secondly, HC is used to manipulate the menstrual cycle with the possibility for associated performance benefits; and thirdly, even though lowering endogenous testosterone levels (Casto et al., 2022) some HC contains testosterone-like androgenic compounds, again with potential or actual performance-enhancing effects (Thompson et al., 2021). Yet, HC is not subject to anti-doping regulation, with women’s right to reproductive control the overriding priority. Indeed, some sports’ governing bodies wish to reserve the right to actively require certain women to take HC as a means of mitigating naturally high testosterone levels—what some critics view as a sort of reverse doping, since it is motivated by performance aims rather than athlete health (Karkazis et al., 2012). I thus consider in this paper how there is more to the process of classifying prohibited substances than stated in the official list of criteria: social context, and social exigencies, are also paramount, in ways that also intersect with gender politics.

3. Hormones and performance

It is beyond the scope of this article to present in detail the complex biochemistry and physiology of androgenic, estrogenic, and progesterone-like hormones (often referred to as the sex hormones), or their contemporary discussion by the social sciences, for which the reader is referred to recent textbooks and monographs (Casey et al., 2016; Cook, 2022; Jordan-Young & Karkazis, 2019). I hereunder only address some aspects relevant to the purpose of my argument.

At birth, human babies are typically classified as either female or male. Since most sports have separate women and men categories, in this paper, I mostly use the proxy terms of women and men, while acknowledging that women may not have been classified as female at birth, and vice versa. While women and men are not as biologically dimorphic as in many other animal species, clear differences can be observed in their hormonal profiles. Both women’s and men’s bodies produce androgens (e.g., testosterone, dihydrotestosterone), estrogens, and progestins, though typically in different quantities (women have lower levels of testosterone while men have lower levels of estrogens and progestins), and rhythmicity (variation related to menstrual cycles, diurnal and possibly seasonal rhythms in women and men, training/over-training) (Handelsman et al., 2018). Second, and of importance for sports performance, are the effects of some of the steroid hormones in comparison with testosterone, in particular concerning its anabolic effects, i.e., increased protein synthesis, and especially that of muscle tissue (Handelsman et al., 2018). Third, testosterone is a pleiotropic hormone and has many other effects. For example, in men, it is associated with changes during puberty such as hair patterns and voice deepening, while also influencing growth spurts and skeletal muscle growth. The latter is believed to explain average differences in muscular development between women and men and average differences in strength and power-based performance between elite adult women and men athletes (Handelsman et al., 2018). Also of relevance for performance is that testosterone stimulates erythropoiesis, resulting on average in a higher hematocrit (fraction of red blood cells in the blood) and hemoglobin mass (the red pigment carrying the oxygen in the red blood cells) in men compared to women, contributing to the average advantage in men for oxygen transport capacity and therefore aerobic performance (Handelsman et al., 2018). Together, these phenotypic differences contribute to the on-average 10 to 20% better performance in men as compared to women in many elite sports, and the need for separate women’s and men’s categories in most elite competitions (Handelsman et al., 2018).

Although testosterone is perceived as the quintessential men’s hormone, it is also present in women. In elite athletes, there are overlapping distributions of total testosterone in blood between women and men, with the lower end of the men’s range (8.8–30.9 nmol/L) being four-to five-fold higher than the upper end of the women’s range (0.4–2.0 nmol/L) (Clark et al., 2019). A study on Olympic athletes reported low testosterone concentrations in 25.4% of men and high testosterone concentrations in 4.8% of women (Sönksen et al., 2018), illustrating the complexity of defining normal ranges separating the sexes. The extent of research into the role of testosterone and other androgens in women still lags behind that in men, but testosterone is essential for women’s healthy functioning (Alexander et al., 2022); Davis & Wahlin-Jacobsen, 2015). Evidence for the role of testosterone metabolism in women’s sexual/reproductive function is rather compelling, as is its role in musculoskeletal health, especially concerning bone mineral density. Less clear, but likely is its cardiovascular health-promoting effect, while its role in breast, ovarian, and endometrial cancer remains to be clarified (Davis & Wahlin-Jacobsen, 2015). Total blood testosterone is seemingly not related to muscle mass and strength, with researchers pointing instead to its free (not bound to protein) fraction. Yet overall, the precise relationships between testosterone levels, muscle function, and athletic performance remain unclear, both in men and women (Alexander et al., 2022).

Estrogens also have important effects on muscle function and quality. Much of the research into the role of estrogens concerns menopausal women who are at risk of osteoporosis and sarcopenia. Estrogens influence muscle contractile properties and attenuate indices of post-exercise muscle damage by stimulating muscle repair and other regenerative processes, including the activation and proliferation of muscle satellite cells (Enns & Tiidus, 2010). In their comprehensive review, Pellegrino et al. mention a meta-analysis of 23 studies including nearly 10,000 post-menopausal women, assessing the effects of estrogen-based hormonal replacement therapy (HRT) on muscle strength, which concluded that estrogen-based HRT provides small (∼5%) improvements in strength, even in the absence of hypertrophy. A more recent meta-analysis examining the effects of estrogen HRT use on muscle mass specifically of post-menopausal women across 12 randomized clinical trials, found a small but insignificant retention of lean muscle mass in estrogen HRT users (Pellegrino et al., 2022).

In contrast to estrogen, which is frequently used for menopausal symptoms, there is less literature about progesterone since it is infrequently supplemented in isolation. Two recent reviews summarized what is known about sex hormones and muscle function in women (Alexander et al., 2022; Rosa-Caldwell & Greene, 2019). Also in women, sex steroids play important roles in the regulation of skeletal muscle mass and function. The free fractions of testosterone and progesterone in serum are associated with the regulation of muscle mass, while estrogens seem primarily involved in mediating muscle contractile function in conjunction with other sex hormones. Muscle strength does not seem to be directly associated with any hormone in isolation when at physiological concentrations in circulating blood. In contrast, it seems that intramuscular sex hormone concentrations may be more strongly associated with muscle size and function than the circulating forms.

4. Why little is known about the menstrual cycle and performance

From its onset in the late 19^th century, modern sport has remained essentially an enterprise dominated by men. Women were ignored or explicitly excluded, to then at best become half-heartily tolerated but controlled, while only during the last decades the efforts for inclusion become more pronounced (Gebel et al., 2022). Even though nowadays half of the competitions at the Olympics concern events for women, only during the Paris Olympics in 2024 should parity in participation numbers be finally reached. Meanwhile, prize money in elite sports competitions remains heavily skewed, and sports governance continues to be a state of affairs dominated by men, be it at regional, national, or international levels. In parallel, scientific research into sports and exercise has also mainly concerned men, and only recently more methodic study of women engaging in sports and exercise has taken off but has not reached parity either (Costello et al., 2014; Elliott-Sale et al., 2021). The consequence is that rather little is known about the specificities of women’s sports, and their biology and physiology.

One truly neglected area of research is that into the relationship between the menstrual cycle and performance (Bruinvels et al., 2017). Summarizing what is known, two recent reviews from 2021 concluded that the currently limited evidence suggests a variable association between the menstrual cycle and several performance measures, such as endurance, power resistance, ligament stiffness, decision-making skills, psychology, and competitiveness (Carmichael et al., 2021; Meignié et al., 2021). Pending further well-designed research into this field it appears that different sports performance-related parameters can be affected during the menstrual cycle among elite athletes, but the parameters themselves and the magnitude and the direction of the effects remain, for the time being, rather inconclusive. Importantly, there is a need to individualize, since for an athlete who has strong peri-menstrual symptoms, the menstrual cycle will certainly negatively influence performance. When asked if their menstrual cycle influences their training and performance 42% of female athletes said it did (Bruinvels et al., 2016), a finding confirmed in another recent study (Ekenros et al., 2022). Apart from these effects related to menstrual cycling, women with menstrual disorders associated with low serum estradiol and progesterone levels have an attenuated anabolic hormone response to acute resistance exercise, suggesting that menstrual disorders characterized by low ovarian hormone levels may affect exercise-induced changes in anabolic hormones in women, with potential effects on performance (Nakamura & Aizawa, 2016).

5. Hormonal contraception use by athletes

The careers of female athletes coincide with their lifetime procreative capacity and this imposes a complex balancing act between engaging in a sports career and family planning strategies, for which HC can be of use. The mechanism by which HC works, in short, is that a combination of extraneous estrogen and progesterone similars can prevent ovulation and thus make fecundation and implantation of a fetus impossible. HC is an umbrella term comprising a wide range of types (e.g., combined, mono- bi- or tri-phasic), and delivery methods (oral, injected, implanted, skin patches). Over the 70+ years of its existence, the choice of compounds and their dosages has evolved and nowadays represents a resounding success (Dhont, 2010). While the primary reason for HC use is to prevent pregnancy, it can also be used to alleviate dysmenorrhea (pain associated with menstruation), menorrhagia (heavy menstruation), other peri-menstrual symptoms, and several other medical ailments. HC thus allows manipulation of the female cycle besides its contraceptive effect. The female cycle can be manipulated for example by extending the phase of pill intake and/or shortening the phase of withdrawal. Cycle manipulation also allows for controlling the timing of the withdrawal bleeding and potential painful side effects of menses (Castanier et al., 2021).

The prevalence of HC use (mainly in the form of oral preparations) among female athletes varies between 20 and 70%, depending on the country, sport, and athletic level (Castanier et al., 2021). A recent study from Australia reported that a third of athletes were using HC, 71% to avoid pregnancy, 38% to control or regulate the menstrual cycle, and 36% to reduce menstrual pain (Clarke et al., 2021). In physically active and competitive women, such manipulation of the female cycle using HC seems widespread (Castanier et al., 2021; Clarke et al., 2021; Sulak et al., 2002). Deliberate manipulation of timing, frequency, and amount of menstrual bleeding may be performed by up to 60–75% of competitive women athletes, for reasons of special events, holidays, convenience, but also sports competition (Castanier et al., 2021). Arguably, choosing not to menstruate at all, or to plan for bleeding periods, with HC, would be altering the ‘normal’, and therefore (potentially) performance enhancing, while it can also be argued that HC use by women with very strong perimenstrual symptoms can be seen as medically justified, since alleviating the suffering that can be labeled as ‘abnormal’, and therefore performance-restoring.

However, it remains unclear whether such HC cycle manipulation is justified when it comes to maximizing athletic performance, because of a lack of good research into the question (Jonge, 2003; Romance et al., 2019; Römer et al., 2022; Thompson et al., 2020). It also remains unclear whether some specific types of HC might affect physiological parameters related to strength performance. Some studies have looked at the effects of HC on indices of muscle physiology. A 10-week supervised progressive resistance training program in women on HC was associated with a trend toward a greater increase in muscle mass and a significantly greater increase in type I muscle fiber area compared to controls. Yet, the use of HC did not influence the overall increase in muscle strength related to training (Dalgaard et al., 2019). In another study in young untrained women, HC increased the expression of skeletal muscle regulatory factor 4 and satellite cell number following 10 weeks of resistance training compared with nonusers, suggesting a potential performance-relevant effect (Oxfeldt et al., 2020). A recent systematic review found significant anabolic effects in a dose-dependent manner, suggesting that there may be some potentially interesting effects for strength and power activities (Römer et al., 2022).

The principle of HC is the suppression of the natural cyclic fluctuations of estrogen and progesterone. Most contemporary combined oral HC contains an estrogen component together with one of eight progestins. The latter vary in potency, androgenic effects, and interaction with estrogens. Androgenicity indicates the ability to produce masculine characteristics and could have implications for muscle strength and function. There is little research comparing low and high androgenic HC and for now, the results are equivocal, even though it is plausible that increased levels of the exogenous hormones in high-androgenicity oral HC could have a positive influence on high-velocity strength (Thompson et al., 2021). It follows that the effects of HC on performance remain to be further scrutinized, and individualized. Importantly, the published research results only concern women taking the recommended amounts of the compounds in their oral contraceptive, and the effects of supra-physiological amounts with an intent to improve performance remain unknown.

6. HC should not but could be forbidden in elite sport

As mentioned previously, to be included on the Prohibited List a substance must meet at least two of the following three criteria: 1) potential or actual enhancement of performance; 2) potential or actual health risk; 3) counter to the Spirit of Sport. I now address the question of whether these criteria are met when an athlete uses HC. For example, if an athlete decides to use HC to regulate her menstrual cycle with the intent to seek a performance enhancement this would seem to tick all three criteria. Firstly, for some women it could make a (real or perceived) difference, for example for an athlete with strong perimenstrual symptoms, and this would thus meet the performance enhancement criterion. Secondly, since HC use comes with an increased health risk for breast cancer or stroke, the health criterion is also met (Teal & Edelman, 2021). Thirdly, the use of any hormone to seek an advantage over another athlete would be against the Spirit of Sport, also for substances or methods not (yet) on the Prohibited List. I hereunder discuss these three points in more detail.

a. The performance enhancement criterion

As summarized above, the effects of HC on performance are not clear yet, but there is certainly potential for performance-enhancing effects in women with strong perimenstrual syndromes and also for androgenic HC. Furthermore, a recent systematic review found a dose-dependency of anabolic effects of HC, arguably enough to consider HC use as potentially performance-enhancing. Manipulation of the menstrual cycle with HC with the express intent to improve performance is prevalent. The prevalence of HC use for its potential anabolic effects is unknown. Taken together and since the performance criterion in the Code explicitly mentions that a potential is enough to consider a substance for inclusion on the Prohibited List, it follows that with or without the intent of the athlete the first criterion is met if an athlete uses HC.

b. The health risk criterion

The second criterion mentions that a potential or actual health risk is sufficient to consider the inclusion of a substance on the Prohibited List. HC brings both health benefits and risks. Even today, but less than in the past thanks to changes in HC composition, the health risks of HC remain real. Depending on their composition they are linked to for example thrombo-embolism and possibly breast cancer (Bonfiglio & Pietro, 2021; Skeith et al., 2021). Furthermore, it is imaginable that some athletes, alone, or with the help of medical support personnel, would decide to increase the dosage of some HC compound to amplify for example an androgenic effect. Such would not be without risk, as that of masculinization, and could further an already increased risk for breast cancer from HC (Shamseddin et al., 2021). Also, the second criterion would thus seem to be met if an athlete decides to use HC, for whatever reason.

c. The Spirit of Sport criterion

The third criterion refers to the Spirit of Sport concept. This definition is part of the Code, the main document outlining WADA’s anti-doping policy (WADA, 2021). Doping is herein defined as a transgression of the anti-doping rule. Since HC is not on the Prohibited List implies that its use is, for now, not considered doping. However, several other elements of the Spirit of Sport arguably are reasons to condemn HC use. Notably ‘the perfection of each person’s natural talents’, implies that the use of substances or methods allowing one to go beyond one’s natural talent would go counter to the Spirit of Sport. Since HC changes the natural hormonal milieu also this criterion seems met. The debate on the Spirit of Sport is ongoing and moot. Given the strong moral contempt for an anti-doping rule violation, it would seem that a doping mindset, that is a performance-seeking behavior with means similar to those on the Prohibited List, would be counter to the Spirit of Sport. Even though today HC use is not forbidden, the Spirit of Sport criterion could be used for considering putting HC on the Prohibited List.

7. Conclusions and perspectives

Applying WADA’s three criteria to HC its use could be added to the Prohibited List. However, I am strongly against such inclusion for reasons relating to what the invention of HC has brought to women. The advent of hormonal contraception undoubtedly played an important role in the movement toward more equal rights and opportunities for women in general, and likely also for their participation in hitherto rather exclusively men’s activities such as competitive sports (Dhont, 2010). Today’s sports careers of women generally run in part parallel with their lifetime procreative capacity and this imposes a complex balancing act between engaging in a sports career and family planning strategies (Bø et al., 2016). Given the well-balanced benefit-risk ratio of modern HC, the decision to use it for birth control, to regulate an irregular menstrual cycle, or to diminish peri-menstrual symptoms should be left to the woman (Golobof & Kiley, 2016).

Nevertheless, taking to the letter both WADA’s Code and the criteria used to put a substance or method on the Prohibited List, it seems to me that HC could be forbidden in female sports. As shown before using a similar reductio ad absurdum approach for placebos (Kayser, 2020), this points to the arbitrariness of the principle of the two of three criteria for inclusion of substances on the Prohibited List (Heuberger et al., 2022). As argued elsewhere, my analysis is meant to contribute to the discussion on how to develop better anti-doping policies (Heuberger et al., 2022; Kayser, 2018).

There is a precedent. One type of HC was banned by the IOC in May 1987. HC containing norethindrone was forbidden because of potential confusion when testing for doping with metabolites from nandrolone, a forbidden androgenic corticosteroid. After protests and the discovery that this potential confusion could be adverted with better analytic methods, the ban was lifted (Duda, 1988). Nowadays, with the introduction of the Athlete Blood Passport (ABP) and its steroid module, there is renewed interest since the urine steroid profiles of female athletes differ from those of non-athletes (Eklund et al., 2021). In their ABP an individual athlete serves as their yardstick for acceptable variations of biomarkers between upper and lower boundaries. Steroidal variations during HC use can potentially confound the monitoring of the presence and variation of various steroids for anti-doping purposes. It is now proposed to complete the usual urine matrix with that of blood to better control for such confounding (Moreillon et al., 2022).

In conclusion, the inclusion of substances and methods by the two out of three criteria principle has led to a Prohibited List that is not evidence-based, is too long, and convoluted (Heuberger et al., 2022). This likely contributes to the lack of efficacy of current anti-doping efforts as illustrated by the estimated prevalence of doping in elite sports which remains high (Faiss et al., 2020; Gleaves et al., 2021; Hon et al., 2015; Ulrich et al., 2018;) and a troubling large fraction of doping cases for which there is good reason to believe that there was no intent to improve performance (Hon and Bottenburg, 2017). As argued elsewhere there is a lack of evidence for most substances on the Prohibited List for performance or negative health effects, a lack of transparency and accountability of governance and decision-making by WADA, and the extension of anti-doping policies outside the field of professional sports (Heuberger et al., 2022). The present analysis of the potential inclusion of HC underscores that analysis and reinforces the plea for more science, better governance, and more education in anti-doping.

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Notes

1 It is defined as follows: ‘The spirit of sport is the celebration of the human spirit, body and mind, and is reflected in values we find in and through sport, including: Health; Ethics, fair play and honesty; Athletes’ rights as set forth in the Code; Excellence in performance; Character and education; Fun and joy; Teamwork; Dedication and commitment; Respect for rules and laws; Respect for self and other participants; Courage; Community and solidarity. The spirit of sport is expressed in how we play true. Doping is fundamentally contrary to the spirit of sport.’ (WADA, 2021)