Hypersomatotropism without concurrent diabetes mellitus in cats: 28 cases (2014-2024)

Background Hypersomatotropism (HST) in cats has predominantly been associated with diabetes mellitus (DM) and HST in nondiabetic cats is poorly described. Hypothesis/Objectives To describe the clinical presentation, clinicopathologic findings, and outcome of nondiabetic cats with presumed HST. Animals Twenty-eight client-owned cats. Methods Multi-site retrospective study based on medical records of nondiabetic cats seen at 10 institutions between 2014 and 2024 with presumed HST (elevated serum insulin-like growth factor-1 [IGF-1] ± clinical signs compatible with acromegaly ± documented pituitary enlargement). Clinical presentation, diagnostic findings, and survival times were reviewed. Results Twenty-eight cats with HST were included. Twenty-six cats were males, and 2 cats were females; mean age was 9.5 years (±SD 3.5 years); mean body weight was 7.1 kg (±SD 2.1 kg). The median serum IGF-1 concentration was 1236 ng/mL (range 704-2455 ng/mL). Nineteen of 28 cats (68%) had clinical signs possibly related to acromegaly: prognathia inferior (13/28), weight gain (12/28), broad facial features (10/28), abdominal enlargement (10/28), respiratory stridor (9/28), polyphagia (9/28), and signs of neurological disease (3/28). The most common clinicopathological abnormalities were hyperproteinemia (12/28), serum creatinine above the reference interval (RI) (10/28), and urinary specific gravity below the RI (9/28). Hypertrophic cardiomyopathy phenotype was identified in 8/17 cases. The most common comorbidity was chronic kidney disease (10/28). The median survival time after diagnosis was 24 months (range 1-103 months). Conclusions and clinical importance Hypersomatotropism can present without DM and should be considered in cats with signs suggestive of growth hormone excess or a pituitary tumor.