Blood plasma concentrations of insulin-like growth factor-I (IGF-I) in resting standardbred horses.
Authors: Champion Z J, Breier B H, Ewen W E, Tobin T T, Casey P J
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Blood Plasma IGF-I Concentrations in Standardbred Horses Understanding baseline endocrine profiles in racing populations is essential for distinguishing pathological changes from normal variation, yet little standardised data existed for insulin-like growth factor-I (IGF-I) in standardbred horses. Champion and colleagues sampled 202 racing standardbreds aged 1–8 years across five New Zealand regions, measuring plasma IGF-I via IGFBP-blocked radioimmunoassay to establish a population reference profile and identify key variables affecting hormone concentrations. Age was the dominant factor, with younger horses showing significantly higher IGF-I levels (P<0.05), consistent with patterns in other species; intact males demonstrated significantly elevated IGF-I compared to mares and geldings (P<0.05); and both geographic location and individual trainer practices exerted significant influences (P<0.05) on measured concentrations. These findings underscore that clinical interpretation of IGF-I results requires contextualisation against multiple variables—practitioners should account for age, sex status, and management factors rather than applying universal reference ranges, particularly when evaluating growth disorders, athletic performance, or metabolic concerns in young standardbreds.
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Practical Takeaways
- •IGF-I reference ranges for standardbreds must account for age and sex differences; younger intact males will have naturally higher concentrations
- •Training management and geographic/environmental factors may influence growth hormone axis function and warrant investigation in performance horses
- •Interpretation of IGF-I testing requires consideration of multiple confounding variables beyond simple laboratory values
Key Findings
- •Age significantly affects IGF-I concentrations, with highest levels in younger horses (P<0.05)
- •Intact males have significantly higher IGF-I concentrations compared to mares and geldings (P<0.05)
- •Geographic location and trainer effects significantly influence IGF-I concentrations in racing standardbreds (P<0.05)
- •IGFBP-blocked radioimmunoassay provides valid measurement of equine IGF-I concentrations