Caitlyn Jenner, the 1976 Olympic decathlon champion turned transgender advocate, has ignited a firestorm in women’s sports by directly challenging swimmer Lia Thomas. Speaking on Fox News last week, Jenner declared that biological advantages from male puberty are permanent and irreversible.
The 75-year-old reality star and former athlete revealed her own recent hormone and blood test panels, claiming they demonstrate why even long-term hormone therapy cannot fully erase male physiological benefits. She contrasted her results with documents she says Lia Thomas submitted to FINA in 2022.
Jenner’s testosterone level, after nine years of hormone replacement therapy, sits at 0.8 nmol/L, well within female range. However, her red blood cell count, hemoglobin, and grip strength remain significantly higher than elite cisgender female athletes, data she says proves irreversible skeletal and muscular advantages.
According to Jenner, Thomas’s 2022 FINA submission showed testosterone below 2.5 nmol/L but allegedly omitted critical markers such as bone density, lung capacity, and residual muscle fiber composition. These omissions, Jenner claims, created a misleading picture of complete physiological transition.
The former Olympian argues that Thomas retained broader shoulders, larger hands, longer arms, and a cardiovascular system developed during male puberty. These factors, she insists, translate to permanent performance advantages regardless of hormone suppression duration.
Jenner pointed to her own athletic decline after transitioning at age 65, noting she could no longer approach her former male records yet still outperforms most women in strength-based tests. She called this the “inescapable truth” of male puberty’s lasting imprint.
Thomas, who dominated NCAA women’s swimming in 2022, has remained largely silent since World Aquatics effectively banned transgender women who experienced male puberty from elite female competition. Jenner’s intervention has reopened old wounds.
Critics accuse Jenner of transphobia and weaponizing her identity to undermine another transgender woman. Supporters praise her for speaking uncomfortable scientific truths that protect the integrity of women’s categories in sport.
Medical experts are divided. Some studies show muscle mass drops 5-10% after two years of testosterone suppression, while others document retained advantages in bone length, heart size, and fast-twitch fiber distribution lasting decades.
Jenner concluded her appearance by demanding full transparency of all medical data submitted by transgender athletes. She called on governing bodies to publish complete physiological profiles rather than selective hormone numbers alone.
The controversy arrives as World Athletics, World Aquatics, and cycling have tightened restrictions, while the IOC continues to delegate policy to individual federations. Jenner’s public comparison has intensified calls for standardized testing protocols.
Thomas’s former teammates at Penn have quietly supported Jenner’s stance, though few speak on record. One anonymous swimmer told reporters the locker-room atmosphere in 2022 remained tense long after Thomas stopped competing.
As legal battles mount in the United States over state-level bans, Jenner’s revelation adds a deeply personal dimension. A transgender woman herself, she insists her position stems from lived experience rather than prejudice.
Whether her intervention helps or harms the broader transgender community remains fiercely debated. What is undeniable is that the question of fairness in women’s sport has found its most unlikely and controversial messenger.
The sporting world now waits to see if governing bodies will demand the comprehensive testing Jenner advocates, or if her explosive comparison will be dismissed as another chapter in an already polarized saga.