Mayo Clinic Preprint Reports Testicular Atrophy in Puberty-Blocked Youth, Questions Full Reversibility

Puberty Blocker and Aging Impact on Testicular Cell States and Function

Cohort & registry studies Puberty blockers

Authors: Varshini Murugesh, Megan Ritting, Salem Salem, Syed Mohammed Musheer Aalam, Joaquin Garcia, Asma J Chattha, Yulian Zhao, David JHF Knapp, Guruprasad Kalthur, Candace F Granberg, Nagarajan Kannan
Journal: bioRxiv (preprint, not peer reviewed)
Year: 2024
Source: pubmed.ncbi.nlm.nih.gov/38585884/

Summary

Puberty blockers (drugs that pause puberty) are often called a reversible pause, but little is known about their effect on the testicles. Mayo Clinic researchers examined tissue stored from children having surgery to preserve fertility. All 16 born-male patients with gender dysphoria in their tissue bank had taken puberty blockers. Treated children's tissue showed mild to severe shrinking of the sperm-making tubes; one 12-year-old on a blocker plus oestrogen had 59% of tubes completely shrunken. Detailed cell tests on one 14-year-old after more than four years on blockers found sperm-forming cells stuck at an early stage, and computer models judged the tissue to be like a child's before puberty. The authors say this raises 'a potential concern' about full reversibility. It is an early, unchecked signal: few treated patients, mixed drugs, no follow-up after stopping, no fertility measure.

Key findings

Of 87 patients in a Mayo Clinic bank of children's testicular tissue, 16 (18%) had gender dysphoria. All 16 had taken puberty blockers, and 9 (56%) were on them at the time of fertility-preservation surgery.
The drugs counted as 'puberty blockers' included true blockers (leuprolide, histrelin, triptorelin) but also oestrogen and other hormone drugs (medroxyprogesterone, spironolactone), taken for 3 to 52 months. Average age at surgery was 12.5.
All the patients with gender dysphoria chose surgery to remove tissue rather than giving a sperm sample, because they did not want to or could not ejaculate. 2 of the 9 treated patients had testicle abnormalities when examined.
Looking at about 50 tubes per donor in 19 donors without cancer, the density of cells in the tubes rose with age in untreated children, but showed no change with age in treated children. One 12-year-old on a blocker plus oestrogen for 14 months had 59% of tubes completely shrunken, with tiny calcium deposits.
Detailed gene tests on single cells from one 14-year-old after more than 52 months of treatment (11,199 cells, combined with public data to 130,100 cells) found over 90% of sperm-forming cells stuck at an early stage, and unusual states in the support cells that nurse developing sperm.
A computer model trained on just 10 people (5 children before puberty, 5 young adults) judged the treated 14-year-old's tissue to be like a child's before puberty. The authors themselves say the small training group is a major weakness.
The authors conclude the shrinkage and immature cells 'raise a potential concern' about full reversibility and future fertility. The study did not test recovery after stopping or measure fertility.

Abstract

Spermatogonial stem cell (SSC) acquisition of meiotogenetic state during puberty to produce genetically diverse gametes is blocked by drugs collectively referred as 'puberty blocker' (PB). Investigating the impact of PB on juvenile SSC state and function is challenging due to limited tissue access and clinical data. Herein, we report largest clinically annotated juvenile testicular biorepository with all children with gender dysphoria on chronic PB treatment highlighting shift in pediatric patient demography in US. At the tissue level, we report mild-to-severe sex gland atrophy in PB treated children. We developed most extensive integrated single-cell RNA dataset to date (>100K single cells; 25 patients), merging both public and novel (52 month PB-treated) datasets, alongside innovative computational approach tailed for germ cells and evaluated the impact of PB and aging on SSC. We report novel constitutional ranges for each testicular cell type across the entire age spectrum, distinct effects of treatments on prepubertal vs adult SSC, presence of spermatogenic epithelial cells exhibiting post-meiotic-state, irrespective of age, puberty status, or PB treatment. Further, we defined distinct effects of PB and aging on testicular cell lineage composition, and SSC meiotogenetic state and function. Using single cell data from prepubertal and young adult, we were able to accurately predict sexual maturity based both on overall cell type proportions, as well as on gene expression patterns within each major cell type. Applying these models to a PB-treated patient that they appeared pre-pubertal across the entire tissue. This combined with the noted gland atrophy and abnormalities from the histology data raise a potential concern regarding the complete 'reversibility' and reproductive fitness of SSC. The biorepository, data, and research approach presented in this study provide unique opportunity to explore the impact of PB on testicular reproductive health.

Conclusion

The authors report mild-to-severe testicular tubule atrophy in puberty-blocker-treated children and an immature, prepubertal-like profile in the testis of a patient treated for more than 52 months. They conclude that, combined with the gland atrophy and histological abnormalities, this raises 'a potential concern regarding the complete reversibility and reproductive fitness' of spermatogonial stem cells. They also report rare post-meiotic (spermatid-like) cells in prepubertal tissue, irrespective of age, puberty status or treatment. They say the biorepository, data and research approach 'provide unique opportunity to explore the impact of PB on testicular reproductive health.'

Methodological limitations

Not peer reviewed: Posted online as a preprint on 27 March 2024. The US medical research database PubMed labels it not yet reviewed by a journal, and no journal version was found as of October 2026.
Very few treated patients: The detailed cell findings come from one patient on blockers. Only 9 of 16 patients with gender dysphoria were on blockers at surgery, and the microscope analysis of 19 donors does not clearly say how many were treated.
No information on recovery: No patient was followed after stopping treatment, so worries about permanent effects are guesses from how the tissue looks, not something observed.
Mixed with other hormones: The 'puberty blocker' group included oestrogen and other hormone drugs. The worst shrinkage (59% of tubes) was in a child on a blocker plus oestrogen, so the effect of blockers alone cannot be separated from oestrogen or testosterone-blocking drugs.
Expected effect, or damage?: Puberty blockers are meant to keep tissue at a pre-puberty stage, so finding child-like tissue in a treated patient is partly what treatment is designed to do. The key question, whether tissue matures normally after stopping, was not studied.
Weak computer-model evidence: The models were trained on only 10 people and wrongly judged a 5-month-old's tissue to be mature. The authors call the small training group a major limit on how far the results apply.
Comparison data from elsewhere: The cell analysis merges public data from other labs, ages and conditions (including adult trans women on oestrogen or testosterone blockers) with one new sample. Differences in how tissue was collected and processed may affect the comparisons.
Unusual group: Patients were those having fertility-preservation surgery, and all with gender dysphoria chose tissue removal because they did not want to or could not ejaculate. Two of nine treated patients had testicle abnormalities, so they may not represent all young people on blockers.
New, untested tissue measures: The cell-density method for grading tube development, and its split into two 'response states', are new and not shown to predict later sperm production.
No fertility results: Sperm counts, hormone recovery after stopping and actual fertility were not measured. Media reports describing proven 'irreversible infertility' go beyond the data.
Sloppy reporting: The summary of the paper says over 100,000 cells while the main text reports 130,100. Some sentences in the summary are garbled and key methods are thinly described, issues peer review would usually fix.

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Summary

Key findings

Abstract

Conclusion