Screening diabetic cats for feline hypersomatotropism (HS) is currently dependent on using a radioimmunoassay (RIA) for measurement of growth hormone or insulin-like growth factor 1 (IGF-1), both of which require radioactivity, are costly and have limited availability. Performance of an enzyme-linked immunosorbent assay (ELISA) using anti-human IGF-1 antibodies was assessed. Total IGF-1 was determined in diabetic cat samples across a wide range of IGF-concentrations using a previously validated RIA (serum: 92 cats; plasma: 31 cats). Repeat IGF-1 measurement was then performed using the ELISA-system. Mean IGF-1 recovery after serial dilution proved satisfactory with a correlation coefficient of 0.96 (serum) and 0.97 (plasma). Appropriate precision was established [intra-assay coefficient of variation (CV) 9.5 ± 2% (serum) and 13.6 ± 7% (plasma); inter-assay CV 11.4 ± 4% (serum) and 7.6 ± 6% (plasma)] and significant effect of hyperlipidaemia, haemoglobinaemia, bilirubinaemia and storage was excluded, with the exception of an increase in serum IGF-1 when left at room temperature for more than 24 h. ELISA concentrations correlated significantly with RIA concentrations (serum Pearson r(2): 0.75; plasma: 0.83, P <0.001). Receiver operating characteristics analysis showed an area under the curve of 0.99 (serum) and 0.96 (plasma), and indicated high diagnostic accuracy for categorising a diabetic cat correctly as suspicious for HS at a serum IGF-1 cut-off of 997 ng/ml (sensitivity, 100%; specificity, 88.1%). The current study is the first to validate an easy-to-use and economical IGF-1 ELISA for the screening for HS among diabetic cats, which is important given the suspected significant prevalence of HS-induced diabetes mellitus.

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Hypersomathotropism is an important feline endocrinopathy, induced by a pituitary growth hormone secreting adenoma. Up until present, most of the diagnosed acromegalic cats were diagnosed previously with insulin dependent diabetes mellitus. Hypersomathotropism needs imperative exclusion when dealing with poor blood glucose control and insulin resistance. The present paper describes hypersomathotropism diagnosis protocol in two insulin resistant diabetic felines.Two diabetic domestic short hair cats presenting marked insulin resistance and poor blood glucose control were evaluated. Diagnosis protocol included anamnesis, physical evaluation and general and speci ic biochemistry analysis. Diagnosis con irmation was obtained on contrast enhanced intracranial MRI and morphopathological examination.Both cases displayed marked insulin resistance with 1.5 IU/kg/administration in the male cat (10.5 IU/administration) and 2.4 I.U./kg/administration in the female cat (12 I.U./administration). On physical examination have been observed a slight inferior prognathia on the female cat, clubbed paws on the male cat, broad facial features and obesity (female: 5kg; male: 7 kg). Repeated blood glucose curves con irmed persistent hyperglycaemia >450 mg/dl (61-124 mg/dl) with different doses of insulin. Speci ic biochemistry revealed an increased concentration of insulin like growth factor-1 determination >1000 ng/ml (208 -443 ng/ml), above the cut-off for hypersomathotropism diagnosis. Contrast enhanced MRI revealed an enlarged pituitary gland con irming hypersomathotropism. Haematoxylin eosin examination of the pituitary tissue revealed acidophilic cells consistent with growth hormone producing cells.Systemic manifestations are masked by diabetes mellitus clinical signs leading to a high error degree in diagnostic establishment and administration of highly dangerous doses of insulin. With accurate diagnosis, case management and speci ic treatment can be applied accordingly and in the favor of patient quality of life.

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