Puberty blockers cause atrophy in testes, leading to concerns their effects are irreversible: Mayo Clinic study

The preprint study, which has yet to be peer-reviewed, looked at samples from the Mayo Clinic’s Pediatric Testicular Biobank for Fertility Preservation, which has been recruiting patients since 2015.

Researchers looked at testicular specimens from 87 young biological boys under the age of 18 who were undergoing fertility preservation surgery for a variety of reasons. Of this group, 16 were gender dysphoric boys, ranging in age from 10 to 16, and who began identifying as transgender between the ages of 2 and 15, independent journalist Christina Buttons reported.

At the time of the surgery, 9 of these 16 patients had already begun taking puberty blockers, with time on the drug ranging between 3 and 52 months.

The researchers stated that all of these 16 patients would go on to take puberty blockers.

Two of the nine transgender patients who were on puberty blockers exhibited unusual testicular features upon examination, with one patient having abnormalities in both testes, including incomplete development of the tunica albuginea that protects the testes. The other patient had a right testicle that was hard to detect.

Over 400 testicular biopsy samples were used in tissue-level analysis, with comparisons between those who took the drug and those who did not showing varying levels of abnormal testicular development.

In one case of a 12-year-old patient who had been on puberty blockers for 14 months, 59 percent of the patient’s testes showed complete atrophy as well as the presence of microlithiasis, where clusters of calcium form in the testes.

The researchers also took a detailed look at individual cells from a 14-year-old patient’s testes. The patient had been on puberty blockers for over 4 years, and over 90 percent of the cells responsible for sperm production had been stunted at an early age.

The authors also found cell-specific changes, such as "altered expression patterns of puberty-associated genes in endothelial cells," and found that puberty blockers may cause alterations in gene expression which affects processes for the growth and function of these cells.

The authors noted that there is "limited data on the long-term consequences of PB exposure on testicular reproductive health."

Advocates for the drug have stated that it essentially serves as a pause button for puberty, and that the effects are fully reversible. The study calls that assumption into question.

In response to the study, JK Rowling wrote, "Steward bells began ringing, but it was hard to learn anything... the Titanic’s passengers began exploring for an answer."