Background and Aim: At around 2-3 months of age in humans there is a surge of gonadatrophins and androgens, now known as minipuberty [1, 2]. The postnatal testosterone surge has been thought to be important for normal early germ cell development including transformation of gonocytes into spermatogonia stem cells (SSC). Mouse gonocyte transformation occurs between day 2-6 [3,4], but whether there is a postnatal hormonal surge is unclear. This study aims to determine whether there is a surge in gonadatrophins and androgen postnally that might be important for germ cell development, enable us to use the mouse as a model for human minipuberty.
Materials and methods: Testes and blood serum were collected from male C57Bl/6 foetuses at embryonic (E) 17 and pups at postnatal (P) 0 (birth) to P10. Serum and testis testosterone and serum FSH were measured using LC–MS/MS and IFMA respectively. Gene expression of FSHR, LHR and AMH were measured by qPCR.
Results: There was a clear peak of testosterone at P3 in both serum and testis. Serum FSH was low at birth, then gradually increased to significantly higher levels after P7. FSHR expression peaked (>2 fold) at around P4, then gradually dropped. LHR was high at E17 (7 fold) then significantly dropped to low level at P0 onwards. There was elevated AMH expression at birth, then gradually dropped to low levels (<0.5 fold) after P5.
Discussion and conclusion: These results showed a brief surge in testosterone levels between days 1-3 in newborn mice, which is similar to the occurrence of minipuberty in infant boys. This suggests that the same changes in the hypothalamic-pituitary-gonadal axis are occurring in mice as humans. FSHR reached peak expression soon after testosterone peaked, which indicates that FSH may play an important role during minipuberty on the gonocyte transformation.