Bone, Heart Risk to Transgender Youth Receiving Puberty Blockers and Hormones: Study

A long-supressed, taxpayer-funded report on transgender youth found that treatments with puberty blockers and hormones could have lasting negative impacts on bone density and heart health, among other health issues.

The Oversight Project, a watchdog group, obtained the final report of “The Impact of Early Medical Treatment in Transgender Youth” and shared it with The Daily Signal.

The National Institutes of Health first allocated a nine-year grant for up to $10 million for a study through the Children’s Hospital of Los Angeles. The study was led by Dr. Johanna Olson-Kennedy, who specializes in “gender-affirming care.”

Neither the hospital nor Olson-Kennedy, now in private practice, responded to inquiries for this story.

The study was long-awaited. The New York Times first reported in late 2024 that the study of almost 100 children would not be published because Olson-Kennedy feared the findings would be “weaponized.”

The study included minors as young as 8. The sample receiving puberty blockers included participants as old as 16, while the sample receiving transgender hormone treatments included participants as old as 20.

The report warns of potential bone density deficits for youth entering the “pubertal suppression cohort of the study,” who had lower baseline bone-mineral density compared with the general population.

“At baseline, these youth already have lower amounts of calcium in their bones (bone-mineral density) than the general population; this may be related to lower levels of physical activity,” the report says.

The physical health impact warrants scrutiny, said Oversight Project Director of State Litigation Neal Cornett.

“Low bone density can affect whether someone could be an athlete, or affect how tall you grow,” Cornett told The Daily Signal. “It could put people in a similar situation to osteoporosis.”

The report said gender-affirming hormones, or GAH, triggered unfavorable cholesterol changes, decreasing HDL, viewed as the “good” cholesterol, and increasing LDL, the “bad” cholesterol.

“By two years after starting GAH, youth starting estrogen showed increases in HDL cholesterol and decreases in LDL cholesterol, while youth starting testosterone showed decreases in HDL cholesterol and increases in LDL cholesterol,” the report notes. “These changes are consistent with known effects of these hormones.”

The report further noted the treatments would affect reproductive health and infertility.

“The third major objective is to establish an archive of tissue samples to enable future translational research into long-term impacts of gender-affirming care on fertility, and cellular mechanisms underlying treatment response,” the report says.

It later adds, “Subjects undergoing gonadectomy/oophorectomy or seeking fertility preservation options, including oocyte/sperm cryopreservation, will be invited to participate in the tissue repository.”

Among biological females prescribed testosterone, 6.5% developed abnormally high red blood cell concentrations, or hematocrit exceeding 50%, which can elevate potential risks for vascular events.

“Hemoglobin and hematocrit decreased in adolescents prescribed estradiol (-1.4 mg/dL and -3.6%, respectively) and increased in adolescents prescribed testosterone (+1.0 mg/dL and +3.9%) by 6 months after gender-affirming hormone therapy (GAHT) initiation,” the report notes. “Thirteen (6.5%) participants prescribed testosterone had hematocrit > 50% during GAHT.”