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ECS and EMS in horses: An overview

ECS and EMS in horses: An overview of two common metabolic diseases

Metabolic diseases such as equine Cushing's syndrome (ECS) and equine metabolic syndrome (EMS) are becoming increasingly common in horses. These two diseases affect different aspects of hormonal and metabolic balance, but share many common symptoms and risk factors. In this blog post, you'll learn what ECS and EMS are, how they develop, what symptoms they cause, and how they can be diagnosed and treated.

What is equine Cushing's syndrome (ECS)?

Equine Cushing's syndrome, also known as pituitary pars intermedia dysfunction (PPID), is a hormonal disorder caused by a malfunction of the pituitary gland. This gland produces several hormones, including prolactin and adrenocorticotropic hormone (ACTH), which stimulates the production of cortisol from the adrenal cortex. In ECS, the part of the pituitary gland responsible for producing ACTH is overactive, leading to increased production of this hormone.

Causes:
The exact cause of ECS is not yet fully understood, but overproduction of ACTH is caused by degeneration of the pituitary gland tissue, often associated with advancing age. The risk increases with age, with older horses being particularly affected.

Symptoms of the ECS

The symptoms of ECS are very diverse and can manifest to varying degrees:

  • Shedding disorders : A common symptom is the long-lasting, thick winter coat change, even in summer, or the presence of "hoods" (thicker, matted areas of fur).

  • Polyuria/Polydipsia : Frequent urination (polyuria) and increased thirst (polydipsia) are also typical signs.

  • Muscle loss : Muscle loss, especially in the back and lumbar muscles, is a common symptom.

  • Cushing's hoof problems : Laminitis is a serious risk in ECS horses because elevated cortisol levels can impair the blood supply to the hoof.

  • Weight loss : Despite a good appetite and adequate feed intake, horses often lose weight.

  • Reduced performance : Horses with ECS are less efficient and often show reduced endurance.

Diagnosis of the ECS

ECS is usually diagnosed through specific blood tests that measure ACTH levels. If ECS is suspected, the veterinarian may also perform a dexamethasone inhibition test or a TRH stimulation test. The veterinarian may also look for typical clinical signs.

Treatment of the ECS

Treatment of the ECS focuses primarily on regulating hormone levels and managing symptoms:

  • Pergolide : Pergolide, a dopamine agonist, is the main drug used to treat ECS. It targets the overactive pituitary gland and reduces ACTH production.

  • Dietary management : A well-balanced diet is important to avoid obesity and control insulin levels. A diet rich in fiber and low in sugar and starch is recommended.

  • Hoof management : Since laminitis is a common problem, regular hoof checks and, if necessary, adjustments in housing and care should be made.

  • Regular health checks : Regular monitoring of the horse by the veterinarian is necessary to monitor progress and adjust therapy.

What is equine metabolic syndrome (EMS)?

Equine Metabolic Syndrome (EMS) is a metabolic disorder associated with insulin resistance. This condition causes the horse's cells to no longer respond adequately to insulin, leading to elevated insulin levels in the blood. This is similar to that seen in humans with type 2 diabetes. EMS is often associated with obesity and poor feed utilization and is particularly common in horses with little exercise and a diet that is too high in energy.

Causes:
The exact causes of EMS are not fully understood, but genetic predisposition, obesity, lack of exercise, and a high-sugar and starch diet play a role. Insulin resistance often occurs in horses that consume too much sugar and starch from grain or high-energy grass feeds.

Symptoms of EMS

The symptoms of EMS are often very similar to those of the ECS and can look like this:

  • Overweight and obesity : The so-called "fat deposits" in the neck area (sunburn on the neck) and the torso are particularly common.

  • Laminitis : Horses with EMS are particularly susceptible to acute laminitis, a very painful and potentially dangerous condition in which the hoof is inflamed.

  • Recurrent hoof problems : EMS can also have long-term effects on hoof health.

  • Hormonal imbalances : EMS can also lead to hormonal disorders that can affect the fertility and cycle of mares.

Diagnosis of EMS

EMS is usually diagnosed through blood tests, particularly measuring insulin levels and the glucose tolerance test (ITT). The veterinarian may also assess the horse's weight and body condition, looking for typical signs of EMS.

Treatment of EMS

The treatment of EMS includes several important measures:

  • Dietary management : A transition to a low-fat, low-sugar diet is crucial. Horses with EMS should be fed a high-fiber, low-sugar, low-starch diet, often using hay instead of grass or feed mixes high in sugar and starch.

  • Exercise and posture : Exercise is an important component of EMS treatment. A regular exercise program helps control weight and improve insulin sensitivity.

  • Drug treatment : In some cases, medications such as metformin or levothyroxine can be used to improve insulin resistance and regulate glucose metabolism.

  • Hoof health monitoring : Due to the increased risk of laminitis, horses with EMS must be regularly cared for by a farrier. Special measures to relieve hoof strain may be necessary.

Difference between ECS and EMS

Although ECS and EMS are both hormonal and metabolic disorders, they differ in their cause and type of disorder:

  • Cause : ECS results from a malfunction of the pituitary gland, leading to excessive production of ACTH. EMS, on the other hand, is primarily insulin resistance caused by an unhealthy diet and lack of exercise.

  • Symptoms : Both conditions lead to hoof problems and coat changes, but EMS is more strongly associated with obesity and insulin resistance, while ECS is characterized by an overproduction of ACTH and resulting hormonal imbalances.

Conclusion

Both Equine Cushing's Syndrome (ECS) and Equine Metabolic Syndrome (EMS) pose a serious health threat to affected horses and require timely diagnosis and appropriate therapy. Through a combination of medication, nutritional management, and targeted exercise, these conditions can be controlled to improve the horse's quality of life. Regular veterinary checkups and appropriate husbandry are crucial to minimize symptoms and prevent long-term consequences.

Source: Martina Hemm June 2025