Updates on Equine Endocrinological Disorders: PPID and EMS 

This article originally appeared in the Summer 2026 issue of EquiManagement. Sign up here for a FREE subscription to EquiManagement’s quarterly digital or print magazine and any special issues.

At a Boehringer Ingelheim webinar, Kelsey Hart, DVM, PhD, DACVIM (LAIM), the Hodgson Chair of Equine Studies at the University of Georgia College of Veterinary Medicine, presented updates on two main endocrinological disorders in horses. 

Risk Factors for PPID and EMS

In horses older than 15 years, 20% may be affected by pituitary pars intermedia dysfunction (PPID). PPID can affect as many as 30% of horses over 30 years of age. As a progressive disease that develops in middle-aged or older horses, PPID results in excessive release of adrenocorticotropic hormone (ACTH) and related peptides from hyperplasia or adenoma of the pars intermedia tissue of the pituitary gland. This occurs due to degeneration of hypothalamic dopaminergic neurons undergoing oxidative damage.

Hart said equine metabolic syndrome (EMS) might be present in as many as 50% of predisposed breeds—Morgans, Tennessee Walking Horses, Saddlebreds, Arabians, warmbloods, Paso Finos, and some ponies. EMS can occur in any age horse and is often associated with insulin dysfunction (ID), which has genetic and environmental factors leading to adipose-derived endocrine disease and ID. She described EMS as a collection of metabolic and clinical risk factors that consistently includes ID, which then increases the risk of laminitis. Insulin dysfunction arises from a disturbance of the relationship between circulating insulin and glucose, with an exaggerated insulin response to dietary sugar. Inciting causes include excess sugar in a horse’s diet and/or altered gastrointestinal release of incretin hormone. The liver might also reduce insulin clearance, resulting in tissues becoming resistant to insulin. All these scenarios result in hyperinsulinemia. Adiposity also increases the release of adipokines to elicit ID and/or chronic inflammation. 

Hart emphasized that not all EMS horses are obese. Other risk factors besides body condition score for ID include breed, genetics, age (> 5 years of age), diet (especially if high in nonstructural carbohydrates), and PPID status.

Hyperinsulinemia-Associated Laminitis

Of note, said Hart, is that hyperinsulinemia-associated laminitis (HAL) is the cause of 90% of laminitis cases. She added that there is speculation about inappropriate stimulation of insulin-like growth factor 1 (IGF-1) receptors in the digital lamellae of the foot. Proliferation of lamellar cells causes them to elongate so they no longer interdigitate. Insidious and subclinical episodes of lamellar stretching develop at first, with potential progression to clinical laminitis. 

Laminitis risk increases when ID, obesity, and PPID overlap. These are dynamic, progressive diseases with fluctuating hormones. Other factors can also influence interpretation of endocrine responses, including season for PPID testing (autumn is normally associated with higher ACTH levels) and results from the lab doing the testing. Stress, transportation, and pain or illness can also affect insulin and ACTH levels in affected horses. It can be tricky to analyze test results for an accurate interpretation, but they are best corroborated with signalment, history, and the horse’s clinical picture. An accurate diagnosis is necessary for appropriate management and treatment.

SGLT2 Inhibitors

Hart discussed the use of SGLT2 inhibitors to manage ID, especially for severe cases that are nonresponsive to other management efforts. One SGLT2 inhibitor, ertugliflozin, inhibits glucose reabsorption in the kidneys. Caution should be taken to evaluate horses medicated with these substances for potential increases in triglyceride levels, which can become a more significant problem in anorexic horses. Hart stressed that the dose range is a bit unforgiving, so owners must be well-educated on how to administer. In addition, she recommended using SGLT2 inhibitors for only three months, then tapering down and monitoring the horse; SGLT2 inhibitors are not meant for long-term use.

Monitoring Recommendations

Monitoring is critical, she said, taking into consideration a horse’s weight, adiposity, hoof condition, and diet or management changes. Postprandial insulin concentrations are most helpful. Hart said dynamic testing does not always normalize in severe cases of ID. She recommends sampling the horse 1 ½ to 2 hours after normal morning feed, after 2 hours of grazing, or 1 hour after an hour of grazing if green grass is a concern. Postprandial insulin < 50 uIU/ml coincides with a low risk of HAL, whereas horses with levels > 100 uIU/ml have a high risk of HAL.

Related Reading

• Measuring ACTH and CLIP for PPID Horses
• Updates on SGLT2 Inhibitors for Horses
• Recognizing Early Lamellar Structural Failure in Performance Horses

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