Study adds early behavior data on deslorelin use in cats: full analysis

A newly published study in Veterinary Sciences offers fresh insight into how cats may behave after hormonal sterilization with deslorelin implants, an area where evidence has lagged behind growing clinical interest. The multicenter paper compared pet parent-reported behavioral changes after surgical sterilization with changes seen during two phases of deslorelin treatment: the first two weeks after implantation, described as the flare-up phase, and the three-month downregulation phase. The topline finding was straightforward: females were more likely than males to show noticeable flare-up behavior, while cats in downregulation showed marked declines in several unwanted reproductive behaviors. (mdpi.com)

That matters because feline reproductive control is no longer a one-track conversation centered only on surgery. The WSAVA 2024 reproduction guidelines emphasize individualized, science-based decision-making for dogs and cats, and deslorelin has been gaining traction as a reversible option in selected patients. In Europe, Virbac said Suprelorin received an extension of its marketing authorization in June 2022 for use in male cats, reflecting broader commercial and clinical momentum around medical neutering in felines. Earlier studies had already shown reproductive suppression and reductions in sexual behaviors in tomcats, but direct comparisons with surgically sterilized cats, especially around behavior, have been limited. (wsava.org)

In the new study, researchers from centers in Slovenia and Italy collected 66 survey responses: 24 for surgically sterilized cats, 24 during flare-up, and 18 during downregulation. They evaluated 19 behaviors and clinical changes, including reproductive behavior, urine marking, vocalization, aggression, affection, activity, and appetite. During the flare-up phase, the most relevant reported increases were excessive vocalization, affection toward the pet parent, attention seeking, disobedience, reproductive behavior, physical activity, and urine marking, while appetite decreased in a meaningful share of cats. During downregulation, the most relevant changes were decreases in reproductive behavior, urine marking, intact male cat urine odor, disobedience, and physical activity, alongside increases in attention seeking, affection, appetite, and fearfulness. (mdpi.com)

The sex split in flare-up behavior was one of the more clinically useful details. The authors reported that eight female cats in the flare-up group showed behavioral flare-up, while none of the males met the study’s flare-up criteria. In the paper’s discussion, the authors note that queens implanted during anestrus or interestrus may be more likely to show flare-up behavior, and they caution that the study was based on pet parent observations alone, meaning silent heats or subtler hormonal effects could have been missed. (mdpi.com)

The comparison with surgery is likely to draw the most professional interest. After recalculating relevant responses, the authors found that downregulated cats had significantly greater decreases than surgically sterilized cats in urine marking, excessive vocalization, intact male cat urine odor, and disobedience. At the same time, the paper is careful about its own limitations: small sample sizes, different group compositions, possible recall and observation bias, and the fact that pet parents may have perceived the post-downregulation improvement more strongly after first seeing flare-up behavior. Funding also came in part from Virbac Animal Health, which supplied some of the implants used by one study site, although the authors declared no conflicts of interest. (mdpi.com)

Expert guidance and prior literature help put those findings in context. WSAVA’s guidelines note that deslorelin can be part of reproductive management in small animals, but they also highlight important species- and sex-specific effects. Prior feline literature has described deslorelin as a promising reversible tool for suppressing fertility and sex hormone-related behaviors, while also recognizing the temporary stimulatory phase that can precede downregulation. In other words, the new study doesn’t overturn existing knowledge so much as add more behavior-focused, practice-level detail that clinicians can use in exam-room conversations. (wsava.org)

Why it matters: For veterinarians, the practical value here is expectation setting. Pet parents considering hormonal sterilization may be motivated by reversibility, anesthesia concerns, breeding management, or behavior. This study suggests those conversations should include two different time horizons: a short-term window when some cats, especially females, may show more reproductive-type behaviors, and a later window when undesirable behaviors may decline, in some cases more noticeably than after surgery. That doesn’t make deslorelin a universal substitute for gonadectomy, but it does support a more nuanced discussion about case selection, timing, household management, and follow-up. (mdpi.com)

What to watch: The next step is better-quality comparative evidence, ideally prospective studies with larger feline populations, standardized behavioral assessments, and longer follow-up to clarify durability, sex differences, and how closely pet parent-reported improvements track objective behavioral change. (mdpi.com)