Data on the prevalence of insulin dysregulation (ID)—a hallmark of equine metabolic syndrome and a significant risk factor for laminitis—in U.S. horses is limited. Most prevalence studies have been performed on ponies from the U.K. and Australia. But what about sport horses? Insulin dysregulation in this population might be underrecognized because these horses don’t always look like your obvious metabolic cases.
During a presentation at the 2025 Equine Sports Medicine Symposium, Kimberly Hallowell, DVM, DACVIM, a PhD student in the Schnabel Lab at North Carolina State University’s College of Veterinary Medicine, in Raleigh, shared early findings from a study funded by The Foundation for the Horse on the prevalence of ID and subclinical laminitis in sport horses.
Research Objectives
“Insulin dysregulation is the No. 1 risk factor for endocrinopathic laminitis,” she explained, citing 45% of these laminitis cases go unrecognized by horse owners, and the recurrence rate is 34.1% within a two-year period.
“We need to identify cases before the first clinical episode,” Hallowell said. “In order to do that, we need to understand how common subclinical laminitis is and develop practical screening tools to identify these horses.”
One of the tools to make this possible is a stall-side insulin test, of which there are multiple commercial options available. “They’re super handy because you can have them on your truck and test the horse in the moment when you’re trying to decide if you can give a horse steroids for its lameness,” she explained. “The problem we have right now is we don’t have a lot of peer-reviewed field data on these tests—there might be inaccuracies we need to understand.”
The objectives of the current study are threefold:
- Determine the prevalence of ID in a sport horse population using an oral sugar test and identify predictor variables.
- Determine the prevalence of radiographic evidence of laminitis in a sport horse population.
- Assess agreement between a stall side insulin assay and a validated lab assay.
Study Population
The study involved 140 horses with no history of ID presenting to NC State University’s orthopedic surgery and sports medicine service and 40 horses from local performance horse farms. All horses were fasted from grain for at least 12 hours and from hay for 3-6 hours. The researchers logged each horse’s body condition score and cresty neck score and measured baseline insulin, leptin, and adiponectin levels before performing an oral sugar test. They also took lateral radiographs of all four feet and assessed them for evidence of laminitis.
Research Findings
Hallowell said 23% of the study horses were diagnosed with ID based on the test results. Of those, only 10% were diagnosed based on baseline insulin values. Preliminary data show 48% of the first 100 horses evaluated had at least one radiographic marker of laminitis, and 14% had multiple markers. Analysis of predictor variables is underway, but preliminary screening indicates that body condition score and cresty neck score may not be predictive of ID.
As for assay agreement data, Hallowell said they found a strong correlation between stall-side insulin test data and the lab assay.
Findings from this ongoing study reveal that ID is common in sport horses and requires dynamic insulin testing to diagnose. “Practitioners cannot rely on physical appearance,” said Hallowell. “It’s not a good predictor of whether a horse is ID.”
One in seven sport horses in the study had multiple radiographic markers of laminitis. “This highlights the importance of routine balance films,” she said. “Otherwise, we don’t know if evidence is preexisting or an acute episode, and we can intervene sooner.”
Related Reading
- How Endocrine Disorders Impact Equine Athletes
- Effects of Pasture and Obesity on ID and Adiponectin in Horses
- New Point-of-Care ACTH Assay in Horses
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