Evaluation of the combined glucose-insulin and intravenous glucose tolerance tests for insulin dysregulation diagnosis in donkeys.
Authors: Mendoza Francisco Javier, Mejia-Moreira Sebastian, Buchanan Ben R, Toribio Ramiro E, Perez-Ecija Alejandro
Journal: Equine veterinary journal
Summary
# Insulin Dysregulation Testing in Donkeys: Establishing Diagnostic Protocols Insulin dysregulation and donkey metabolic syndrome (DMS) are increasingly recognised clinical problems in donkeys, yet unlike horses, no validated diagnostic criteria or insulin cut-off values exist for this species—a gap that compromises early detection and management of at-risk animals. Researchers evaluated resting insulin concentrations alongside two dynamic tests (combined glucose-insulin test [CGIT] and intravenous glucose tolerance test [IVGTT]) in 80 donkeys, six of which met DMS criteria based on recurrent laminitis history, elevated body and neck condition scores, or elevated baseline insulin (>20 µIU/mL) and leptin (>12 ng/mL) concentrations. When interpreted using equine metabolic syndrome guidelines, the IVGTT identified five donkeys with insulin dysregulation whilst CGIT classified only two to three donkeys depending on the parameter examined; dysregulated donkeys demonstrated predictably lower glucose-to-insulin ratios and insulin sensitivity indices (QUICKI and RISQI) alongside elevated insulin resistance markers (MIRG and HOMA-B%). Although these findings suggest equine diagnostic thresholds may translate to donkeys, the small sample size and poor concordance between tests indicate that species-specific baseline insulin cut-offs and further validation studies are essential before these protocols can be confidently applied in practice. For equine professionals managing donkeys with metabolic concerns, this work provides a starting point for dynamic testing interpretation but highlights the urgent need for larger, multi-centre studies to establish reliable diagnostic standards for donkey-specific insulin dysregulation.
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Practical Takeaways
- •When evaluating donkeys suspected of metabolic syndrome, IVGTT appears more sensitive than CGIT for detecting insulin dysregulation, though both tests warrant consideration
- •Existing equine metabolic syndrome diagnostic criteria show promise for donkey assessment but cannot be directly applied without establishing donkey-specific insulin thresholds
- •Baseline serum insulin and leptin concentrations should be evaluated alongside dynamic testing, as single measurements may not adequately capture metabolic dysfunction in donkeys
Key Findings
- •IVGTT detected more insulin dysregulation cases (5 donkeys) than CGIT (2-3 donkeys) when applied to donkeys using equine metabolic syndrome guidelines
- •Insulin dysregulated donkeys showed significantly lower glucose/insulin ratios, QUICKI and RISQI indices, and higher insulin/glucose ratios, MIRG and HOMA-B% values
- •This is the first study evaluating dynamic diagnostic tests for insulin dysregulation and donkey metabolic syndrome in a donkey population
- •EMS diagnostic recommendations appear applicable to donkeys but require establishment of species-specific baseline insulin cut-off values