Serial Changes in Insulin-Like Growth Factor 1 and Impact on Hypersomatotropism-Screening in Feline Diabetes Mellitus
27th ECVIM-CA Congress, 2017
V.L. Woolhead; L. Teo Whee Wen; C. Scudder; R. Gostelow; G. Harman; Y. Forcada; D.B. Church; S.J.M. Niessen
Royal Veterinary College, North Mymms, UK

Hypersomatotropism [HS] is the underlying cause of diabetes mellitus in a substantial number of diabetic cats. Serum insulin-like growth factor-1 [IGF-1] measurement is currently the test of choice, with concentrations greater than 1000 ng/ml having a 95% positive predictive value. Therefore, all commercial laboratories currently use this value as a cut-off to indicate likely HS presence. However, endogenous insulin availability affects IGF-1 synthesis, thereby possibly reducing test sensitivity, especially in newly insulin-treated diabetic acromegalics.

This study's two main questions were: 1. How many newly diagnosed and treated diabetic cats demonstrate serum IGF-1 initially not suggestive to subsequently become suggestive of HS using this cut-off (1000 ng/ml)? 2. How strong is the correlation between endogenous insulin and IGF-1 concentrations in untreated diabetic cats?

Serial blood samples of diabetic cats were prospectively recruited from first opinion UK veterinary practices within 180 days of initiating insulin treatment. Serum IGF-1 and basal serum endogenous insulin were evaluated using a validated and commercially offered RIA and ELISA, respectively; the latter in untreated diabetic cats only. Mann Whitney test was used to compare groups and Spearman rank correlation coefficient to assess correlation between endogenous insulin and IGF-1; p<0.05 was considered significant. Serial blood samples of 219 cats were recruited (two samples: 103 cats; three: 55; four: 44; ≥five: 17). Sixty-two (28.3%) cats had at least one IGF-1 measurement >1000 ng/ml (median 1576 ng/ml, range 1001–>2000); a median of 0.6 units/kg/injection insulin (range 0–2.4) was administered. Of the cats with IGF-1 >1000 ng/ml, 20 (9.1%) initially showed IGF-1 <1000 ng/ml; therefore, the attending clinician could have discarded the possibility of HS in these patients. Median subsequent IGF-1 increase was 594 ng/ml (range 71–1495), having initially received a median of 73 days of insulin treatment (range 25–154). Basal endogenous insulin in untreated diabetic cats with IGF-1 <1000 ng/ml (n=106; median 29.0 ng/l, range 9.2–791) was significantly lower than in those with IGF-1 >1000 ng/ml (n=15; median 64.2 ng/l, range 9.2–490; p=0.024). A moderate positive correlation (rs=0.42, p<0.0001) was detected between endogenous insulin and IGF-1 in untreated cats. In this study, approximately 1 in 10 newly diagnosed diabetic cats with an IGF-1 suggestive of underlying HS, based on the currently advocated cut-off, will initially show a negative value using this cut-off. Lower endogenous insulin, which moderately correlates with IGF-1, and/or suboptimal current cut-off value advice, could be contributing factors.

Disclosures

No disclosures to report.

  

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

V.L. Woolhead
Royal Veterinary College
North Mymms, UK


MAIN : ESVE : Serial Changes in Insulin-Like Growth Factor 1
Powered By VIN
SAID=27