EXPRESS: Successful response to cabergoline treatment in a non-diabetic cat with hypersomatotropism and pituitary macroadenoma

Case summary: A 12-year-old male neutered domestic shorthair cat was referred with severe polyphagia, polydipsia, polyuria, weight gain, and signs of neurological disease, including blindness, head tilt, and ataxia. Magnetic resonance imaging (MRI) identified a suprasellar mass consistent with a pituitary macroadenoma. Hypersomatotropism (HST) was diagnosed based on phenotypic changes compatible with acromegaly and an abnormally high serum insulin-like growth factor 1 (IGF-1) concentration (1253 ng/ml). Medical treatment with cabergoline monotherapy (10 µg/kg PO q24h) was prescribed. Progressive improvement of clinical signs was observed, accompanied by a gradual decrease in serum IGF-1 concentrations. Based on clinical and hormonal response, the dosing interval was sequentially extended to q48h and subsequently to q72h. By week 16 of treatment, signs of neurological disease had resolved and serum IGF-1 concentration had normalized (749 ng/ml), while visual deficits persisted. By week 30, signs of neurological disease remained absent, serum IGF-1 concentration was maintained within the reference interval, and diabetes mellitus did not develop. Cabergoline was well tolerated, with mild gastrointestinal signs reported early in the course of treatment. Relevance and novel information: this report describes a non-diabetic cat with HST secondary to a pituitary macroadenoma achieving sustained clinical and biochemical control with cabergoline monotherapy. This case demonstrates that dopamine agonist might be an effective medical option in selected non-diabetic cats with HST, even in the presence of a large pituitary mass and signs of neurological disease.