Diagnosis of equine endocrinopathies: The value of measuring blood glucose during an oral glucose test.
Authors: de Laat M A, Sillence M N
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Oral Glucose Testing and Blood Glucose Measurement in Equine Endocrinopathies De Laat and Sillence's retrospective analysis of 149 horses and ponies examined whether blood glucose responses during oral glucose testing (OGT) could reliably indicate insulin dysregulation (ID) or pituitary pars intermedia dysfunction (PPID)—conditions routinely assessed in practice through serum insulin and plasma ACTH measurement. Although blood glucose change during OGT showed weak positive correlations with serum insulin increase (r = 0.36), body condition score (r = 0.26) and cresty neck score (r = 0.38), there was substantial overlap between diagnostic groups, with metabolically healthy animals showing median glucose increases of 2.2 mM compared to 3.8 mM in ID cases and 6.1 mM in animals with both conditions. Critical confounding factors emerged: miniature horses demonstrated more than double the glucose response of full-sized horses (5.25 versus 2.4 mM), and dextrose dose significantly influenced results. The findings indicate that whilst blood glucose measurement may support cresty neck scoring when assessing ID risk, it cannot serve as a standalone diagnostic tool for either endocrinopathy, and clinicians should continue to rely on insulin and ACTH measurements for definitive diagnosis rather than interpreting OGT glucose responses in isolation.
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Practical Takeaways
- •Do not rely solely on blood glucose changes during OGT to diagnose insulin dysregulation or PPID; use in combination with serum insulin, ACTH, and clinical signs including cresty neck score
- •Be aware that miniature horses and ponies show disproportionately larger glucose responses than full-sized horses during OGT, which may affect interpretation of results across different equine types
- •Standardize dextrose dosing in OGT protocols, as higher doses produce larger glucose responses and may confound diagnostic interpretation
Key Findings
- •Mean blood glucose increase during OGT was 3.41 mM, showing weak positive correlation with serum insulin increase (r=0.36) and cresty neck score (r=0.38)
- •Miniature horses had more than twice the blood glucose response (5.25 mM) compared to full-sized horses (2.4 mM)
- •Metabolically healthy animals showed smaller glucose increase (+2.2 mM) than those with ID (+3.8 mM) or both endocrinopathies (+6.1 mM)
- •Blood glucose response is dose-dependent and variable; basal and post-prandial glucose responses are not appropriate as stand-alone diagnostic markers for ID or PPID