Prevalence of insulin dysregulation in the non-obese stock-type horse and relationship with morphometric neck measurements.
Authors: Heaton C P, Cavinder C A, McClure E N, Smith T, Smith W B, Liburt N, Krotky A, Harris P
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Insulin Dysregulation in Non-Obese Stock-Type Horses Insulin dysregulation frequently develops in obese horses, but whether lean individuals warrant metabolic screening remains unclear. Heaton and colleagues assessed 62 non-obese stock-type horses using oral sugar testing and morphometric neck measurements to determine ID prevalence and evaluate whether neck conformation could serve as a practical screening tool. Despite their normal body condition scores (averaging 5/9), 4.8% of horses demonstrated pathological insulin responses post-glucose challenge, with affected animals showing significantly elevated fasting glucose (121 vs. 105 mg/dL) and fasting insulin (15.7 vs. 10.5 µIU/mL) compared to metabolically normal peers; notably, mares displayed higher baseline insulin than geldings. While neck circumference at the 50% and 75% points weakly correlated with post-glucose insulin concentrations (R² = 0.09), this relationship was too modest to recommend morphometric assessment as a standalone screening tool. These findings suggest that insulin dysregulation exists across the phenotypic spectrum in stock-type horses and should prompt practitioners to perform metabolic testing based on individual risk factors rather than relying solely on visual body condition assessment.
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Practical Takeaways
- •Do not assume non-obese stock-type horses are safe from insulin dysregulation—approximately 1 in 20 may be affected; consider oral sugar testing regardless of body condition score
- •Morphometric neck measurements alone are poor predictors of insulin response and should not be used as screening tools; formal metabolic testing remains necessary for accurate assessment
- •Sex differences exist in baseline insulin levels; mares warrant particular attention for ID screening given their higher pre-insulin concentrations
Key Findings
- •4.8% of non-obese stock-type horses (3/62) demonstrated insulin dysregulation despite normal body condition score, indicating ID occurs independent of obesity phenotype
- •Horses with ID had significantly higher pre-glucose (121.0 vs 105.3 mg/dL) and pre-insulin (15.7 vs 10.5 µIU/mL) than normal responders
- •Weak positive correlation between neck circumference at 50% length (NC50) and post-glucose response (r=0.30, P=0.04), explaining only 9% of variance
- •Mares demonstrated significantly higher pre-insulin levels than geldings (11.7 vs 9.4 µIU/mL), suggesting sex-based differences in insulin regulation