Equine Metabolic Syndrome and Equine Cushing’s Disease

Equine Metabolic Syndrome EMS and Equine Cushings Disease also known as Pars Pituitary Intermedia Dysfunction or PPID are reasonably common conditions we encounter in our horses. This article will deal primarily with EMS but because PPID can be a cause of increased insulin levels in horses it needs to be mentioned as well.
The terms used to describe these metabolic disorders can add to an already complicated picture. Some of these terms are
Hyperinsulinemia Elevated circulating insulin which can be transient after eating or chronic. Chronic hyperinsulinemia can cause insulin resistance.

Equine Insulin Resistance IR Tissues and organs resist insulin signalling.
Equine Metabolic Syndrome EMS The terms EMS and IR tend to be used interchangeably. The term EMS is more correct as it comprises the constellation of signs that include hyperinsulinemia abnormal fat deposits altered fat metabolism hypertension and risk for laminitis.
Pars Pituitary Intermedia Dysfunction PPID Commonly known as Cushings Disease. It is distinct from EMS although horses with PPID can also have hyperinsulinemia.
It is estimated that about 20 percent of horses over the age of 15 will develop PPID while it is thought that about 10 to 20 percent of horses are insulin resistant to some degree. EMS and PPID can share some common clinical signs the most devastating of which is laminitis.
Hyperinsulinemia is always a feature of EMS but can also be present with PPID. Hyperinsulinemia is managed with diet and exercise PPID is managed with medication Pergolide diet and exercise.
The EMS metabolic type is largely a result of genetics that have enabled horses to survive and even thrive under adverse conditions. It makes sense to have an efficient metabolism if you are a wild horse in the Nevada desert or a Shetland pony grazing scrubby heather in severe weather. This doesnt work quite so well when the caloric needs of an energyefficient horse are easily met or overmet and exercise is less than optimal. Breeds prone to develop EMS are ponies minis donkeys Arabians Morgans Saddlebreds Tennessee Walkers Rocky Mountain Horses Spanish horses including mustangs and a subset of Quarter Horses. Breeds that do not typically develop EMS are Drafts Thoroughbreds Standardbreds and most Quarter Horses. It is important to note that not all individuals of EMSprone breeds will end up with EMS but if you own one of these breeds managing them prudently and keeping your eyes open for warning signs is always a good idea.
Horses with EMS have abnormally