Active immunisation against GnRH as treatment for unilateral granulosa theca cell tumour in mares.
Authors: Behrendt Daphne, Burger Dominik, Gremmes Steffen, Szunyog Katja, Röthemeier Selena, Sieme Harald
Journal: Equine veterinary journal
Summary
# GnRH Immunisation as an Alternative to Surgery for Ovarian Tumours in Mares Granulosa theca cell tumours (GTCTs) in mares typically present with stallion-like or aggressive behaviour and traditionally require surgical ovariectomy, but this case series explores whether active immunisation against GnRH offers a non-invasive alternative. Four mares with ultrasonographically and hormonally confirmed unilateral GTCTs received two initial vaccinations with Improvac® (days 0 and 13–33), with booster doses administered if behavioural signs recurred, whilst serum hormones (testosterone, oestradiol, progesterone, AMH) and ovarian dimensions were monitored throughout the observation period. Testosterone levels normalised in all mares following the first two vaccinations; AMH decreased in three of four cases and returned to baseline in one; crucially, owners reported resolution of behavioural abnormalities and affected ovaries reduced in size across all four animals, with follow-up extending to seven years in one mare. Although this retrospective case series lacks a control group and standardised protocols, the findings suggest GnRH vaccination warrants investigation as a medical management option for unilateral GTCT, potentially sparing owners the risks and costs of general anaesthesia and ovariectomy whilst preserving contralateral ovarian function. Further prospective studies with larger populations and consistent immunisation protocols are needed to establish efficacy, optimal dosing schedules, and long-term outcomes in this application.
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Practical Takeaways
- •GnRH vaccination offers a non-surgical alternative to ovariectomy for managing unilateral GTCT in mares, eliminating stallion-like behaviour and halting tumour progression
- •Two initial vaccinations followed by booster doses as needed can effectively suppress testosterone production and clinical signs associated with GTCT
- •This approach may be particularly valuable for mares where surgical removal poses anaesthetic or post-operative risks
Key Findings
- •GnRH vaccination (Improvac®) reduced testosterone to baseline levels in all four mares following initial vaccinations
- •Anti-Müllerian hormone (AMH) decreased in three of four mares after second vaccination
- •Owner-reported GTCT-linked behavioural abnormalities ceased in all four cases
- •Affected ovaries diminished in size in all four mares, with tumour growth halted over observation periods up to 7 years