Republican senators launch inquiry into unpublished NIH study on puberty blockers for trans youth

Six Republican senators in a letter to National Institutes of Health Director Monica Bertagnolli said they are “concerned about the transparency” of studies funded by the NIH, the federal agency responsible for conducting and supporting medical research.

Their public statement of concern follows an October New York Times report that a long-awaited study of puberty-blocking drugs had gone unpublished over fears that its findings would be “weaponized” by opponents of transition-related care for minors. 

The letter is signed by GOP Sens. Bill Cassidy (La.), Tommy Tuberville (Ala.), Ted Cruz (Texas), James Lankford (Okla.), Markwayne Mullin (Okla.) and Mike Lee (Utah).

The long-awaited study, led by Dr. Johanna Olson-Kennedy, the medical director of the Center for Transyouth Health and Development at the Children’s Hospital of Los Angeles, began in 2015 as part of a broader, multimillion-dollar effort to evaluate the long-term outcomes of medical treatment for transgender children and adolescents.  

Olson-Kennedy and her colleagues were tasked by NIH with studying the effects of puberty blockers, which prevent physical changes, like the development of breasts or a deepening voice, on children in early puberty struggling with gender dysphoria, or distress that stems from a mismatch between a person’s gender identity and sex at birth.  

Nine years later, the data remains unpublished. In October, Olson-Kennedy told the New York Times that puberty blockers did not necessarily yield mental health improvements, which she said was likely because the children recruited for the study were already doing well when it began. 

Olson-Kennedy said she fears the conclusion will be distorted by those who oppose gender-affirming medical care, including puberty blockers and hormone therapy, for transgender young people, a deeply polarizing and increasingly politically charged area of medicine.  

More than half the nation since 2021 has either heavily restricted or banned some transgender care for minors — and adults, in some cases. This week, the Supreme Court heard arguments in a landmark challenge to a Tennessee law prohibiting gender-affirming care for youth, drawing more than 1,000 demonstrators outside the out. 

“I do not want our work to be weaponized,” Olson-Kennedy said in October. “It has to be exactly on point, clear and concise. And that takes time.” 

In Thursday’s letter, Republican senators accused Olson-Kennedy of holding the study’s findings because they likely “do not support her political agenda.” They referenced an independent review in the U.K., known as the Cass Review, that found only “weak” evidence linking puberty blockers to improved mental health outcomes. 

The Cass Review’s findings, which led the British government to ban the use of puberty blockers for minors outside of clinical trials, are themselves controversial, and health experts and physicians who treat trans youth have spent much of the last 8 months since the report’s publication debating whether it is accurate. 

One assessment, by Yale Law School’s Integrity Project, claims the Cass Review “obscures key findings, misrepresents its own data, and is rife with misapplications of the scientific method.” 

Other peer-reviewed studies in the U.S. have found that puberty blockers are associated with positive mental health outcomes in transgender youth, including reduced depression, anxiety and suicidal ideation. 

Senators on Thursday requested Bertagnolli produce each annual progress report for Olson-Kennedy’s study, writing that doing so would “ensure transparency in medical research.”  

With the exception of Cassidy, each of the senators who signed the letter to NIH has either introduced or co-sponsored federal legislation to ban gender-affirming care for minors. 

Cassidy, ranking member of the Senate Health, Education, Labor, and Pensions (HELP) Committee, is still a skeptic of transition-related care, and earlier this year launched an investigation into medical organizations “promoting” the use of puberty blockers, hormones and surgery for minors. 

Major medical groups, including the American Medical Association and the American Academy of Pediatrics, say gender-affirming health care for transgender adults and minors is medically necessary and can be lifesaving. They reject efforts by state and federal governments to restrict care. 

Republicans in Thursday’s letter conceded that the U.S. lacks federally funded research on trans health care “that could better inform doctors and parents” but stopped short of endorsing any further study. 

“To be clear, we oppose taxpayer funding going toward gender transition interventions for minors. While we recognize that this particular study is observational, we remain concerned that minors lack the ability to fully understand the lifelong outcomes of the interventions studied in this project and provide their consent,” the senators wrote. 

Robert F. Kennedy, Jr., President-elect Trump’s pick to lead the Department of Health and Human Services, which oversees NIH, has similarly opposed gender-affirming care for minors, which health care experts say could threaten federal funding for future studies into the effects of treatment.