Small Animal Internal Medicine Resident Washington State University Pullman, Washington, United States
Abstract:
Background: Hypersomatotropism (HST) is a differential for persistent insulin resistance in cats with diabetes mellitus (DM). Serum IGF-1 >1000 ng/mL has been shown to have a high positive predictive value (95%) for the diagnosis of HST in cats. The prevalence of HST in diabetic cats has been previously described in cohorts outside of North America (14.9-24.8%).
Hypothesis/
Objectives: To determine the prevalence of HST in a cohort of North American diabetic cats. Animals: Fifty client-owned cats with DM.
Methods: Prospective multicenter observational study. Sample size calculation was performed based on European prevalence data and assumptions included an overall prevalence of HST of approximately 25% ± 5% (SD). Diabetic cats were screened using fructosamine and sorted into “controlled” (C, ≤500 µmol/L) or “poorly-controlled” (PC, >500 µmol/L) groups. Study cats were also concurrently screened using IGF-1. Advanced imaging (CT, MRI) was completed on all cats with an IGF-1 >1000 ng/mL.
Results: Nine of 50 cats had a IGF-1>1000 ng/mL. All (9/9) cats screened using advanced imaging met the criteria for a pituitary lesion. Majority (7/9) of the cats with pituitary lesions were castrated male domestic shorthair with an overall median age of 10.0 years (7.8-13.8). The positive predictive value of an IGF-1 > 1000 ng/ml for a pituitary lesion was 100%.
Conclusions and Clinical Importance: This study determined a prevalence of 18% for HST in a small cohort of North American client-owned diabetic cats.
