Deslorelin Implant in a Labrador Retriever with Canine Hypersensitivity-Hyperactivity Syndrome (HSHA): Differential Diagnosis, Benefits and Cautions

Canine hypersensitivity hyperactivity syndrome (HSHA) is a neurodevelopmental behavioural disorder characterized by impaired inhibitory control, hyperactivity, hypersensitivity and attention deficit. This case report describes the long-term management of Snoopy, an intact male Labrador Retriever, a family dog undergoing training as a seizure-detection dog, presenting hypersensitivity, hyperreactivity, and impaired attention. The most clinically impactful signs were apparent absence of satiety, ingestion of non-edible items and severe sleep reduction. A multimodal approach combining pharmacological treatment with fluoxetine and structured behavioural therapy resulted in marked and sustained improvement. However, a behavioural deterioration emerged during adolescence, with new behaviours suggesting a hormonal influence on the clinical presentation. The use of a reversible deslorelin implant led to rapid behavioural stabilization, which was consistent with the hypothesis that this was not merely an HSHA relapse. However, increased food-seeking behaviour and weight gain were observed. After discontinuation of hormonal suppression, behavioural stability was maintained, body weight returned to the pre-implant baseline, and pharmacological treatment was progressively withdrawn. This case highlights the importance of long-term follow-up, adaptive therapeutic strategies, and the potential clinical utility of reversible hormonal interventions in the management of canine behavioural disorders.