“The term the industry is moving toward to describe this type of laminitis is hyperinsulinemia-associated laminitis (HAL),” says Andy Durham, BSc, BVSc, CertEP, DEIM, Dipl. ECEIM, MRCVS, RCVS, European Specialist in Equine Internal Medicine at Liphook Equine Hospital, in Hampshire, U.K. “This term is more specific, as it is telling you what that hormonal imbalance is.”

Horses that develop HAL can’t control their insulin, so they have high circulating blood insulin levels either at rest or when challenged with sugars/starches in the form of a meal or an oral sugar test, adds Amanda Adams, PhD, associate professor at the University of Kentucky’s Gluck Equine Research Center, in Lexington. The high insulin levels are what trigger the events in the hoof that lead to laminitis. “It is thought that the insulin binding to the insulinlike growth factor causes stretching and damage to the laminar tissue in the hoof.” Researchers are still working to understand how high the insulin level must be and for how long for HAL to occur.

Understanding how to prevent this painful disease is one of the best ways for owners to ensure better welfare for their horses.

1. Identity Your Horse’s Risk Factors

Three main categories of factors make horses more likely to develop HAL: Having PPID (formerly known as equine Cushing’s disease) or equine metabolic syndrome (EMS) or being on glucocorticoid drugs (steroids), says Durham. All three of these factors stimulate blood insulin levels and work through the same mechanisms.

“These risk factors are not mutually exclusive,” he adds. “For example, if you have a fit Thoroughbred on glucocorticoids, the risk of HAL is quite low, but if you combine these risk factors and have an EMS pony on steroid medication, that risk will be much higher.”  Identifying these risk factors early can be key to mitigating risk. Adhere to the following recommendations if you know your horse is at risk.

2. Reduce Your Horse’s Risk

Maintaining your horse’s healthy body condition and a diet low in nonstructural carbohydrates (NSCs) can reduce some of the risk. An active horse is at a decreased risk of HAL, says Durham. Therefore, if you have an obese horse that could be at risk for developing insulin dysregulation (ID), our sources recommend adapting his diet and increasing exercise before serious health consequences arise. Consult your veterinarian and equine nutritionist to develop an optimal plan for your horse if you suspect he is at risk of HAL.

Horses suffering from HAL need to be managed to lower their blood insulin levels. “This is not a one-size-fits-all; it will vary for each individual case,” says Adams. “Start with diet changes and exercise, provide a low-nonstructural-carbohydrate diet, remove the horse from pasture, add exercise, and consider additional dietary restriction if required.” For dietary management, she recommends consulting an equine nutritionist who has experience managing horses with insulin dysregulation.

3. Test Insulin Levels Regularly

“The favored explanation is that normally insulin does not interfere with the insulinlike growth factor receptors in the hoof; however, when you have elevated levels of blood insulin the receptors can be stimulated, which interferes with the laminae and disturbs that laminar attachment,” says Durham.

Thus, practitioners recommend monitoring these horses’ insulin levels regularly with bloodwork. “For horses that are at a higher risk of developing HAL, it is a good idea to consider yearly or biyearly wellness exam bloodwork to diagnose insulin dysregulation or monitor insulin levels over time,” says Adams.

The best practice is to rely on blood insulin levels as a guideline to management and not simply focus on a diet that is less than 10% NSCs, adds Durham. If you have a high-risk horse (e.g., overweight, predisposed breed, diagnosed with EMS or PPID), discuss regular testing with your veterinarian.

Sugar does not cause laminitis; rather, insulin does, and because every horse responds to dietary sugar differently, their responses to dietary adjustment will vary, says Durham. Therefore, following that 10% NSC threshold might not be completely reliable. After making dietary management changes, even in consultation with an equine nutritionist, it is optimal to retest blood insulin levels to ensure the updated program has adequately reduced the blood insulin level in that horse, he adds.

“Less than 10% NSC content of the diet for insulin dysregulated horses will work for most, but may not work for all of them; therefore, relying on testing their blood insulin levels to ensure the NSC level of the diet is low enough is ideal.”

4. Consider Pharmacological Treatments

When management changes are not successful, practitioners might recommend pharmacological treatments for reducing the risk of HAL in your horse, says Adams. “These might include levothyroxine, metformin, SGLT-2 inhibitors, or GLP-1 analogues.”

Take-Home Message

Understanding the risk factors of HAL and knowing if your horse is at risk is essential. Although sugar plays a crucial role in insulin release, blood insulin testing is vital when making management changes. Adjusting diet and exercise to promote lower blood insulin levels can make a significant difference in preventing hyperinsulinemia-associated laminitis in high-risk horses.