Physicians Warn of Medical Risks In Trans Youth Study Allegedly Funded By Nike

Nike’s latest move in the identity politics arena isn’t a flashy ad campaign — it’s reportedly a quiet, five-year, corporate-backed study examining how puberty blockers and hormone therapy affect athletic performance in transgender-identifying kids. The goal? To see if medically transitioning boys early enough could close the performance gap between males and females in sports.

But is it ethical — or even safe — to alter children’s development to achieve parity in sports?

Two leading physicians, Dr. Marc Siegel and Dr. Nicole Saphier, say no. While both support compassion for gender-dysphoric youth, they’re sounding the alarm about medical risks, ethical red flags and ideological bias driving these interventions.

Dr. Nicole Saphier and Dr. Marc Siegel weighed in on the implications of a Nike-funded study on transgender youth.

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The doctors also explained that athletic advantages for males likely wouldn't be erased by hormone therapy, no matter how early in life the treatments are administered. 

Dr. Siegel pointed out that males have more testosterone than females even in utero — long before puberty begins — affecting development in ways hormone suppression may not reverse.

"I would still be concerned about a competitive advantage in people that are born male, even if they transition over to female — because of skeletal type, because of body type," Siegel said in an exclusive interview with OutKick. "I would be very expectant that a competitive advantage would be retained."

Hormone Therapy Comes With Both Physical And Psychological Risks

As a physician and a mother, Dr. Saphier said she feels "deeply concerned" by reports that Nike is helping to fund a study on adolescent children using hormone blockers.

"The potential physical and mental health risks of these interventions, especially in young, developing bodies, cannot be overstated," Saphier said in a statement to OutKick. "Puberty is a critical window for growth, bone density, and emotional maturation, and altering it with hormone blockers can lead to irreversible consequences — ranging from weakened skeletal health and infertility to heightened anxiety and depression."

Siegel similarly emphasized that these treatments could have detrimental effects on patients later in life.

"I’m concerned about the long-term side effects of puberty blockers, especially when joined with gender-affirming hormones, in terms of fertility, bone growth and mental health," Siegel said.

Protesters hold signs advocating for "gender-affirming" care for children.

(Photo by Joshua Stanyer/SOPA Images/LightRocket via Getty Images)

And then there's the question of reversibility.

The popular narrative that puberty blockers are a reversible "pause button" doesn’t hold up to scientific scrutiny — and both physicians urge caution.

When asked if these treatments are truly reversible, Dr. Siegel responded: "I don’t know the answer to that. Nobody knows the answer to that."

He acknowledged that some effects may be reversible, but not all.

"Clearly, a mastectomy is irreversible... castration, mastectomies are irreversible. But as far as puberty blockers themselves, that’s unknown," Siegel said. "[Puberty blockers] are usually accompanied by gender-affirming hormones, and that together can be a big problem for fertility."

Transgender Care For Children: Informed Consent Or Influence?

The issue of informed consent is at the core of this debate. Can children truly understand the lifelong implications of medical transition? Siegel is skeptical.

"How does somebody make an informed decision in childhood?... I think over the age of 18, for sure, is informed consent," he said. "I’m nervous about young teens getting this. And, you know, I understand that someone that decides to [be] the other gender wants to transition before they get hit with puberty, but I’m concerned about the medical risks and the psychological risks of that.

"I’m kind of wondering — who’s making the decision? Is it the child? Is it the parent? Is it the doctor?"

Although the company has seemingly tried to keep it quiet, Nike appears to be helping fund a study on transgender youth athletes as young as 12 years old.

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Saphier voiced similar ethical concerns, taking aim at the integrity of the study Nike is reportedly helping to fund. She specifically pointed to the involvement of researcher Joanna Harper, a biological male who identifies as a woman, who has a clear bias.

"While Dr. Kathryn Ackerman, the principal investigator, is a qualified expert to lead such research, the inclusion of a transgender researcher [Harper] and Nike’s financial backing introduces an implicit bias that undermines the study’s objectivity.

"Science is supposed to be about discovery, not proving preconceived opinions."

Follow the UK’s Lead: The Cass Review

Siegel pointed to the United Kingdom's Cass Review as an important moment in the global debate over youth gender medicine. Commissioned by England’s National Health Service (NHS) and led by pediatrician Dr. Hilary Cass, the 2024 report delivered a comprehensive and independent examination of gender identity services for kids.

Here's what it found:

• Most studies on puberty blockers are low quality, with limited data on long-term outcomes.
• Puberty blockers may harm bone health and fertility.
• The majority of children who start blockers go on to cross-sex hormones, undermining the idea that this is simply a "pause."
• Mental health concerns, like autism and anxiety, often co-occur and require broader evaluation.
• A multidisciplinary approach to care is crucial, emphasizing psychological support over immediate medical intervention.
• Following this review, the NHS has since restricted the use of puberty blockers to clinical trials only.

RELATED: Researcher Withheld Study Results On Puberty-Blockers Because It Showed They Don't Help Kids

"This is one time when we should look to Europe and the United Kingdom for kind of guidance," Siegel said. "Because they have been looking at this issue, and they’re coming out away from the idea of puberty blockers in children and adolescents."

Gender-Confused Children Need Support, Not Drugs

Children need to be protected, not politicized. But with the growing pervasiveness of radical gender ideology, the line between science and social experimentation is getting blurrier by the day.

This reported Nike-funded study on transgender-identifying youth is the latest example — a corporate-sponsored attempt to validate irreversible medical interventions on developing bodies, all in the name of "inclusion."

WATCH: Tomi Lahren, Michele Tafoya Rip Nike Over Alleged Funding Of Puberty-Blocker Study

As Saphier put it: "We need transparent, unbiased research to safeguard our children’s long-term health — not studies influenced by corporate agendas or ideological leanings."

Transgender rights activists rally outside of the U.S. Supreme Court.

(Photo by Kevin Dietsch/Getty Images)

For parents who are facing difficult decisions, Siegel encouraged compassion over haste.

"I think gender dysphoria is real," Siegel said. "And I think that if your child is expressing gender dysphoria, the first and most important thing you could do is show them love, show them a family structure, if you can, and have them see someone that you feel comfortable with, a therapist you feel comfortable with."

Children don’t need questionable medical studies, Nike. They need protection, patience and people who are brave enough to say: not everything should be up for debate.

Marc Siegel, M.D., is a Clinical Professor of Medicine, a practicing internist at NYU Langone Medical Center and serves as the medical director of Doctor Radio on SiriusXM.

Nicole Saphier, M.D., is a Board Certified Physician and Host of the iHeart podcast, 'Wellness Unmasked.'