Donald W. Stremme, VMD
Leuprolide acetate is a long-acting gonadotropin-releasing hormone (GnRH) agonist. Administration initially results in an increase in follicle-stimulating hormone (FSH) and luteinizing hormone (LH) causing transiently elevated testosterone.5 In mammals, testosterone suppression usually follows, often approaching zero. Lupron has been used to suppress testosterone and testicular function in Atlantic bottlenose dolphins (Tursiops truncatus),2,3 to prevent breeding and control aggressive behavior in California sea otters (Enhydra lutris),1,5-7 to control undesirable male-associated behaviors in California Sea Lions (Zalophus californianus),3,5 to control mating aggression in pelagic stingrays (Pteroplatytrygon violacea),12 and for aggression and birth control in lion-tailed macaques (Macaca silenus).10 It has been shown to lower testosterone levels in black-faced, gray kangaroos (Macropus giganteus), African wild dogs (Lycaon pictus) and spectacled bears (Tremarctos ornatus).4 It has also been effective in controlling intermale aggression among gray seals (Halichoerus grypus) and harbor seals (Phoca vitulina) housed together in the same colony (Stremme, unpublished).
Two newly acquired, 2-year-old, unrelated, male African crested porcupines (Hystrix africaeaustralis) began to exhibit aggressive behavior causing wounds requiring veterinary care. Castration was ruled out due to the possibility of future breeding. The monthly form of Lupron was administered intramuscularly to both animals at 0.075 mg/kg every 28 days in an attempt to control the aggression. The animals were anesthetized every 4 weeks with isoflurane, USP to obtain blood to monitor testosterone levels and in some instances to also give the Lupron injections. Serum was sent to the University of Cornell Animal Health Diagnostic Center Endocrinology Laboratory, Ithaca, NY, USA.
Testosterone levels did not drop near zero as expected, and aggressive behavior continued. There was no consistent drop in testosterone levels even when the dose was increased to twice the initial dose (0.150 mg/kg) and three times the initial dose (0.225 mg/kg). In fact, it seemed to rebound and actually increased with the increased dose of Lupron. Leuprolide acetate appears to be ineffective in lowering testosterone levels and in controlling intermale aggressive behavior in African crested porcupines.
The authors would like to thank the biologists at the Adventure Aquarium for their professional observations and support in capturing and handling the animals involved in this project.
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