Combined treatment of pegvisomant and cabergoline in a cat with hypersomatotropism: insulin-like growth factor 1 normalization and control of comorbidities

Case summary: A 19-year-old, spayed female domestic shorthair cat was referred with diabetes mellitus and difficulties in achieving glycemic control. Hypersomatotropism (HST) was diagnosed based on clinical signs compatible with acromegaly (prognathia inferior, broad facial features and abdominal enlargement), increased serum insulin-like growth factor 1 (IGF-1) concentration (4430 ng/ml) and pituitary enlargement (height 4.7 mm). Serum IGF-1 concentrations, biochemical analysis and urinalysis were performed at the time of HST diagnosis and after 10, 20, 30, 60, 120 and 180 days of pegvisomant treatment (PEGV, Somarvet; Pfizer). The cat received PEGV (1 mg/kg SC q24h) in combination with cabergoline (10 μg/kg PO q48h). Serum IGF-1 concentrations decreased abruptly to 396 ng/ml on day 10 of PEGV treatment and blood glucose concentrations also decreased rapidly. Insulin was no longer required after 7 days of PEGV. From day 30 (IGF-1 286 ng/ml), PEGV was administered q48h and the same therapeutic response was maintained after 60 days of treatment (IGF-1 290 ng/ml and diabetic remission). From day 120, PEGV was administered once weekly and normal IGF-1 concentrations (270 ng/ml) were observed after 180 days of treatment. The cat also showed improvements in echocardiographic variables and in her quality of life (QoL) score. Relevance and novel information: This is the first reported case of PEGV plus cabergoline treatment in a cat with HST. The results suggest that the combined treatment of PEGV and cabergoline was associated with normalization of IGF-1 concentrations, diabetic remission, and improvement of cardiovascular function and QoL over a short period.