Hypersomatotropism in diabetic cats in Australia.

Abstract

ObjectivesHypersomatotropisim is an excessive production of growth hormone from the anterior pituitary gland, typically secondary to a pituitary tumour, which causes insulin-resistant diabetes and the clinical syndrome of acromegaly. Studies have shown the prevalence of hypersomatotropism among diabetic cats in the UK, Switzerland and the Netherlands to be in the range of 17.8-26%. The prevalence of hypersomatotropism in Australia is not known. Our objective was to determine the prevalence of hypersomatotropism in diabetic cats in Australia.MethodsResidual serum samples from cats with increased fructosamine or increased blood glucose and a clinical history of diabetes were submitted for the measurement of insulin-like growth factor 1 (IGF-1). Hypersomatotropism was defined as an IGF-1 of 1000 ng/ml or more. The prevalence and associated confidence interval were calculated (Jeffrey's method). Clinicopathological features between diabetic cats with and without hypersomatotropism were compared.ResultsSerum samples from 87 cats were included in the final analysis. IGF-1 was above 1000 ng/ml in 14 cats. The absolute prevalence of IGF-1 was 16%; therefore, the prevalence of hypersomatotropism (IGF-1 levels >1000 ng/ml) in an Australian population is estimated to be in the range of 9.5-24.9%. No significant difference was detected between breed (pedigree vs domestic), sex, age nor location (metropolitan vs regional) in cats with and without hypersomatotropism. Glucose and fructosamine concentrations did not differ between cats with and without hypersomatropism ( = 0.9 and = 0.57, respectively).Conclusions and relevanceHypersomatotropism is an increasingly recognised condition in the feline population as a major contributor to uncontrolled diabetes mellitus. The prevalence of hypersomatotropism in Australian diabetic cats is 16%, which is similar to results from other countries. Clinical features cannot be used to distinguish diabetic cats with and without hypersomatotropism, so screening using a validated IGF-1 assay is necessary.