Pubertal Development Following Paediatric Gonadotoxic Treatment and Immature Testicular Tissue Banking.

Paediatric gonadotoxic treatments can compromise male fertility, yet prospective data systematically tracking pubertal development are scarce. Immature testicular tissue banking (TTB) has been introduced as an experimental fertility preservation option for (pre-)pubertal boys, but its long-term safety and interaction with gonadotoxic treatment are not fully understood. This single-centre prospective cohort study systematically followed 23 boys, treated for malignant or non-malignant conditions, between 2017 and 2025 [median 4.0 (0.1-6.9) years], including 15 who underwent TTB. Unlike previous studies, this research combined repeated assessments of pubertal staging, testicular volumes, parenchymal integrity, reproductive hormones, and bone age and density, enabling a multidimensional evaluation of pubertal development. Gonadotoxic treatments, particularly myeloablative conditioning, were associated with reduced post-pubertal testicular volumes and altered hormone profiles, including elevated luteinising hormone and follicle-stimulating hormone, and reduced inhibin B, while anti-Müllerian hormone remained largely stable. Puberty occurred spontaneously and testosterone production was preserved in all patients. The testicular parenchyma appeared unaffected by the biopsy, and although some biopsied testes showed lower volumes, similar reductions could be observed in non-biopsied testes. These results support the safety of TTB, with no evident adverse effects on testicular structure or function; however, larger multicentric prospective studies are needed to confirm these findings.