Gender, Testosterone, and Sport.

Caitlyn Jenner The incidence of transgender individuals is estimated to be one in 10 000 to 15 000 sex-assigned males (for those designated male at birth who identify as female, also known as transwomen) and one in 30 000 to 40 000 sex-assigned females (for those designated female at birth who identify as male, also known as transmen). There is no published literature ascertaining the incidence of transgender athletes. Appropriate terminology is always important but particularly salient here. Sex and gender are often used interchangeably but have, in fact, quite different meanings. Sex is assigned at birth, typically based on genital phenotype. Gender is socially, culturally, and personally defined. Gender identity is a person’s internal sense of their gender. Cisgender individuals’ gender identity is the same as their sex assigned at birth, whereas transgender individuals’ gender identity differs from their sex assigned at birth. Transsexual is an older term and is considered by many in the transcommunity to be pejorative. Transgender individuals may choose to transition to the gender that matches their identity. Gender transitioning is a complex process that can involve many social, legal, and/or medical components such as use of preferred pronouns, name change on legal documents, hormone therapy, and possibly, although not always, gender confirmation surgery (external genitalia surgery and gonadectomy). The International Olympic Committee (IOC) published the Stockholm Consensus in 2004, which mandated that to compete, transgender athletes needed to 1. undergo gender confirmation surgery, 2. take cross-sex hormone therapy for a minimum of 2 years, 3. have legal recognition of their gender, and 4. have lived as their new gender for 2 years. Athletes who had transitioned before puberty were allowed to compete without restrictions in their transitioned gender sports category. The IOC modified this policy in 2015 to require transgender female athletes to have been transitioned for at least 4 years and maintain testosterone levels below 10 nmol/L) for at least 12 months before and throughout competition. Gender confirmation surgery is no longer required. Male transgender athletes currently have no participation restrictions. The 2011 International Association of Athletics Federations’ (IAAF) guidelines mandated that female athletes have a testosterone level of 5 or less nmol/L continuously for 6 months before a competition. In 2015, the Court of Arbitration for Sport (CAS) suspended this rule for 2 years to await supportive data for this policy. The rule was reinstated in 2018 after the IAAF presented data suggesting a competitive advantage for females with higher testosterone levels inmiddle distance events (eg 400, 800, and1600m). InApril 2019, although theCAS felt the regulations were discriminatory, they upheld the policy after a challenge from track and field athlete Caster Semenya, stating “such discrimination is a necessary, reasonable and proportionate means of achieving the IAAF’s aim of preserving the integrity of female athletics. ” Although these policies were applied only to athletes with differences in sex development (DSD) competing in middle distance races, there are clearly implications for transgender athletes. Transmale athletes take daily exogenous testosterone, and levels can reach that of cisgender males. Transwomen may take additional testosterone blockers if their testosterone levels remain higher than the desired range with estrogen supplementation alone and may also need to take spironolactone, an antiandrogen. Both testosterone and spironolactone are on the World Anti-Doping Association list and, therefore, must be declared by athletes. A retrospective study of 36 transgender athletes examined the impact of cross-sex hormones on muscle mass and testosterone levels. Twelve months after hormone initiation, transgender males had testosterone levels within those considered normal for cisgender males. Transgender female athletes had very low testosterone levels after 12 months of hormone treatment, but muscle mass was still higher than females assigned at birth. Athletic performance was not assessed in this study, which limits application of results to current policies. Defining a normal testosterone level is difficult for multiple reasons: (1) Testosterone production is influenced mainly by luteinizing hormone release, which is pulsatile, (2) Levels vary throughout the day (peak in the morning, decline over the day, and increase again in the evening), (3) Levels change with age (men’s slowly decline and women’s decline severely at menopause), (4) Levels vary by time of year (peak in the fall), and (5) Levels vary over a menstrual cycle (peak during periovulation). Exercise and athletic competition have also been shown to increase levels.Recent data suggest that the current testosterone upper limit levelsmaybe toohigh andmaybeneeded to be limited further. Although normal testosterone levels are difficult to quantify and threshold levels are not uniformly agreed upon, they remain the basis of many policy guidelines. Submitted for publication December 23, 2019; accepted March 30, 2020.