The Effect of Testicular Heat Insult on Hormones and Sperm

Effect of Testicular Heat Insult on Hormones and Sperm - hot stallionThis study investigated the effect of testicular heat insult on hormones and  spermatological consequences following experimentally induced heat stress in stallions, with particular focus on Sertoli cell-derived biomarkers — anti-Müllerian hormone (AMH) and inhibin-B — as potential indicators of testicular function.

Methods:

  • Six stallions underwent scrotal insulation via thermal blanket twice daily for two consecutive days, elevating intratesticular temperature by approximately 10°C
  • Animals were monitored weekly for 98 days post-insult
  • Assessments included sperm kinematics (CASA), morphology, oxidative stress markers, and membrane integrity
  • Serum concentrations of testosterone, estrone sulfate, AMH, and inhibin-B were measured via ELISA or RIA as appropriate
  • Sperm quality was evaluated by CASA (IVOS, HRI)
  • Lipid peroxidation, plasma membrane stability (MPAI) and superoxide anion generation were assessed by flow cytometry
  • Sperm morphology by differential phase interference contrast microscope

Key Findings:

  • Testosterone & estrone sulfate (interstitial markers): positively correlated with motility, progressive motility, and concentration; negatively correlated with morphological defects
  • Inhibin-B (tubular marker): positively correlated with sperm concentration and negatively with total defects
  • AMH: showed no significant correlation with any evaluated sperm parameter

Conclusions:

  • Testosterone, estrone sulfate, and inhibin-B serve as reliable biomarkers for monitoring testicular damage and recovery following  testicular heat insult in stallions
  • AMH, despite its Sertoli cell origin, may lack utility as a fertility marker in heat-stress contexts
  • Results suggest differential sensitivity among tubular compartment hormones in response to heat-induced spermatogenic disruption

(Cavalero TMS, Frasson MS, Trinque CM, Canuto LEF, Freitas-Dell’Aqua CP, Conley AJ, Alvarenga MA, Dell’Aqua Jr JA, Papa FO. 2025. Hormonal changes and sperm quality of stallions after testicular thermal insult. JEVS 145:105273 – Presented in Association with and by Permission of the International Society for Equine Reproduction)