Equine Cushing Syndrome

What is Cushing's?

➡️ Video tip: In this video you will learn everything you need to know about Equine Cushing's disease (PPID) in horses: What is Cushing's? What are the symptoms and how can you best help your horse? From diagnosis to treatment and feeding - important tips to improve your horse's life!

Equine Cushing's syndrome (scientifically PPID, Pituitary Pars Intermedia Dysfunction) is the most common metabolic disorder in older horses. The hormonal disorder originates in the pituitary gland and leads to an imbalance in the entire hormonal system. The term "Cushing's" is more familiar to horse owners.

Cushing's is typical of older horses: studies from Australia and the UK show that around 20% of horses over the age of 15 suffer from it - one in five horses in this age group is affected. In horses between the ages of 16 and 29, the prevalence rises to 64%, and in horses over the age of 30 it is as high as 95%. In rare cases, Cushing's also occurs in younger horses.

A diseased horse has a disturbed hormonal balance, which affects the metabolism and changes both the behavior and the external appearance. Although Cushing's cannot be cured, the symptoms can be treated well with targeted therapy so that the horse can continue to lead a life worth living.

How does Cushing's manifest itself?

The course of Cushing's disease (PPID) can vary greatly, as can the severity of the symptoms. The three most common signs are a poor coat change with a long, curly coat, muscle loss with emaciation and laminitis. Many people initially think of Cushing's as a horse with a shaggy, curly coat. While good coat care and clipping can help, laminitis is far more critical. Around 50% of Cushing's horses develop laminitis, especially if the condition is left untreated. New research suggests that up to 70% of laminitis cases in the fall are caused by Cushing's, and are generally due to impaired sugar metabolism like Cushing's.

Since PPID often begins with subtle behavioral changes, the disease is difficult to detect in its early stages. The first signs include fatigue, exhaustion without exertion and a dull coat. In older horses in particular, it is difficult to distinguish Cushing's from normal signs of ageing, as symptoms such as muscle loss in the back can indicate both.

The symptom complex also makes it difficult to differentiate from equine metabolic syndrome (EMS). Some horses show "pseudo-Cushing's" symptoms even though they have another disease such as EMS, equine asthma or laminitis.

Other symptoms that may indicate Cushing's disease:

• Laminitis, tendency to hoof ulcers, bad horn
• Insulin resistance (similar to diabetes), which favors laminitis
• Heavy sweating without a recognizable cause
• Increased drinking and urination (polydipsia/polyuria) due to kidney disorders
• Visual impairment up to blindness
• Muscle atrophy, especially in the back
• Weight loss
• Fat deposits (over the eyes, unhealthy pads on the neck and croup)
• Poor wound healing
• Infertility
• Milk production in non-pregnant mares
• Susceptibility to infection
• Fatigue and loss of performance to the point of lethargy

Early detection and targeted treatment of PPID are crucial to improve the horse's quality of life and prevent secondary diseases such as laminitis.

The Cause of Equine Cushing's disease 

The exact causes of Equine Cushing's disease (PPID) have not yet been conclusively clarified scientifically, but there are some assumptions. What is known is that a disorder in the hypothalamus triggers a chain reaction between the hypothalamus, pituitary gland and adrenal cortex. As control centers, the hypothalamus and pituitary gland regulate the hormone balance and keep the horse's bodily functions in equilibrium.

This chain reaction begins with a reduced release of dopamine in the hypothalamus, which normally prevents the pituitary gland from releasing excessive amounts of the hormone ACTH (adrenocorticotropic hormone). In older horses with Cushing's, however, the dopamine-producing cells die off more quickly, so that less dopamine is released. Without this dopamine control, the pituitary gland begins to produce ACTH uncontrollably, which can lead to an enlargement of the pituitary gland and even tumor-like growths (adenomas).

Consequences for the horse's body

‍Theincreased release of ACTH stimulates the adrenal cortex to produce large amounts of cortisol, a stress hormone that causes the typical Cushing's symptoms. The rising cortisol level puts the body in a state of permanent alarm and constant stress. This weakens the immune system and increases susceptibility to infections and laminitis. Symptoms such as lethargy and listlessness are also linked to the reduced release of dopamine.

It is unclear why the dopamine-producing cells die off more quickly. Some researchers suspect that factors such as a high-sugar diet, obesity due to lack of exercise and stress due to unsuitable posture could play a role. Long-term administration of cortisone could also contribute to the development of Cushing's disease.

Diagnosis of Cushing's disease in horses

➡️ Video tip: In this video, vet Dr. Alexandra Diefenbach explains how Equine Cushing's disease (PPID) is diagnosed and which steps are important in the course of treatment. Find out how the vet carries out the ACTH test, which additional tests may be useful and how targeted therapy can help your horse to lead a healthy life despite Cushing's.

Cushing's is an insidious disease that initially manifests itself through subtle behavioral changes before visible physical symptoms appear. Diagnosis often begins with a suspected diagnosis based on typical clinical changes. If PPID is suspected, the vet can confirm this with a simple blood test in which the ACTH level is measured.

ACTH levels fluctuate depending on the time of year: in healthy horses, the normal value is below 29 pg/ml from November to July and below 47 pg/ml from August to October. In horses with Cushing's disease, the values are significantly higher; values above 50 pg/ml are already considered critical, and values above 100 pg/ml are a clear sign of Equine Cushing's Syndrome.

However, the diagnosis of Cushing's is not always easy, as it can be difficult to obtain a clear result from a blood sample alone, especially in the early stages and at certain times of the year. In such cases, a TRH stimulation test can be helpful. The horse is administered a drug that either stimulates or inhibits the pituitary gland. The ACTH level is measured both before and after administration of the medication and a result is available after around 30 minutes. Some vets and clinics combine this test with the dexamethasone suppression test, which is somewhat more complex.

The best time for a Cushing's examination is from August to October, as the ACTH level in horses with Cushing's is significantly higher in the fall than in healthy horses, allowing for a more precise diagnosis.

Treatment of Cushing horses

Equine Cushing's syndrome cannot be cured, but it can be treated. Lifelong treatment with medication can curb hormone overproduction and prevent secondary diseases such as laminitis. Regular medication can also prevent the pituitary gland from proliferating, which could otherwise affect other areas of the brain.

For treatment, it is important that horse owners develop an individual treatment plan together with the vet. There is often significant relief of symptoms just a few weeks after starting treatment. The horse should be carefully introduced to the medication in order to avoid possible side effects such as loss of appetite, tiredness or colic.

Drug therapy: In Germany, there is only one approved drug for the treatment of Cushing's disease: Prascend (active ingredient: pergolide mesilate). Prascend replaces the messenger substance dopamine, as a result of which the pituitary gland produces less ACTH and the cortisol level remains stable. Studies from Switzerland show that 90% of patients experience a rapid improvement in symptoms with a daily dosage of 0.5 to 1 mg per kg of body weight. The dosage often needs to be adjusted after some time; the vet should therefore carry out an annual check-up - ideally in the fall.

Additional measures for well-being:In addition to medication, there are other ways to support the horse's quality of life:

• Carry out hoof care, dental checks, worming and vaccinations regularly
• Shear if necessary to avoid skin problems and support thermoregulation
• Cover up in winter to prevent an excessively thick coat
• Regular cleaning prevents felt spots
• Keep the stall clean and provide thick bedding, especially if the horse is urinating more (polyuria)
• Sufficient exercise adapted to your state of health to prevent obesity
• Treat small wounds immediately to prevent infection
• Avoid stress to keep the hormone balance stable

These measures can noticeably improve the well-being of a horse suffering from Cushing's disease.

Cushing's prognosis

The diagnosis of Cushing's is initially a shock for horse owners, but it is by no means the end. With the right combination of medication, appropriate feeding and sufficient exercise, horses with this hormonal disease can remain healthy and fit for many years to come. However, consistent treatment is essential to keep the symptoms - especially laminitis - under control.

Laminitis is one of the most serious consequences of Cushing's and can severely limit the horse's quality of life, to the point where redemption becomes unavoidable. Therefore, a veterinarian should always closely monitor and individualize the treatment of a horse with Cushing's disease.

Feeding Cushing's horses correctly

A horse with Cushing's syndrome can also be supported sensibly in terms of feed. As horses with Cushing's have an increased need for micronutrients, it is important to ensure that they receive highly bioavailable minerals and vitamins in organic compounds. At the same time, it is important to keep a close eye on the amount fed and adjust it upwards or downwards if necessary. Good feeding makes an important contribution to improving the Cushing's horse's quality of life. Here you will find an overview of the feedstuffs:

What is a Cushing's horse not allowed to eat?

A diet low in starch and sugar is crucial for Cushing's horses in order to relieve their metabolism and reduce the risk of secondary diseases such as laminitis. Certain feedstuffs should therefore be avoided:

• Sugary foods: Molasses-based muesli, treats with added sugar and other high-sugar foods are unsuitable as they increase the blood sugar level and put a strain on the hormone balance.
• Cereal products: Grain contains starch, which is converted to sugar in the digestive process. Horses with Cushing's disease should therefore avoid feed with a high grain content.
• Pasture grass: Especially in spring and fall, when pasture grass contains a lot of fructan (a type of sugar), grazing can be problematic. Fresh grass often contains high amounts of sugar, which can increase the risk of laminitis. Limited access to the pasture, possibly with a muzzle, can be a solution here to control intake.
• High-starch feed: Feed with high amounts of starch, such as maize or oats, should also be avoided, as the starch is converted into sugar during the digestive process and places an unnecessary burden on the metabolism.

Instead, Cushing's horses benefit from being fed sufficient roughage such as hay, which supports the intestinal flora and is low in starch and sugar. In some cases, hay can also be soaked to flush out excess carbohydrates.

Equine Cushing's syndrome: Summarized

Equine Cushing's disease, also known as PPID, is one of the most common metabolic diseases in older horses and affects the entire hormonal system. The symptoms often develop gradually and include coat changes, laminitis and a general weakening of the immune system. As Cushing's cannot be cured, targeted and long-term treatment remains crucial to maintain the horse's well-being.

Early detection and individually tailored therapy with medication, adapted feeding and regular exercise are the best measures to ensure a good quality of life for the horse. With these supportive treatment strategies, many Cushing's horses can remain healthy and fit for many years despite their disease. Close contact with the vet and regular health checks are essential in order to prevent secondary diseases and optimally adapt the treatment

Cushing's: The most important questions and answers

How old do Cushing's horses get?

No exact age can be given for the life expectancy of a horse with Cushing 's. Each case differs as much as the symptoms, and the horse's treatment and attitude also have a great influence on its life with Cushing's. In most cases, the first symptoms appear from the age of 15 years. If one gets clarity early on with the help of an ACTH test and starts treatment immediately and permanently, the horse's well-being can be maintained and even increased. There are even horses suffering from PPID that have lived up to 37 years.

How much does a Cushing's or ACTH test cost?

The ACTH test is performed by a veterinarian who wants to be paid for his travel and service, as well as the laboratory test. For the performance alone, one must calculate with about 60 € or more.

If the diagnosis is positive, the drug Prascend must then be administered once a day and permanently. Monthly costs of 60 to 120 € can be expected. If additional treatments are required, for example by a farrier, the monthly costs will be significantly higher.

Can I ride a Cushing's horse?

With Cushing's the cortisol level, the stress hormone, rises sharply. The cortisol level in Cushing's horses as low as possible, as this would otherwise only exacerbate the symptoms. Nevertheless, the horse should be exercised with consistent intensity and frequency in order to stop the rapid muscle breakdown and the development of severe obesity. However, you should take a closer look at how much you expect your horse to do. Riding should therefore be adapted to the horse's state of health. Extensive warm-up and dry riding phases are essential. Alternatively, you can keep the horse busy with sensible exercises from the ground. If a sport horse develops Cushing's disease, the sporting ambitions must also be adapted.

How can I prevent Cushing's disease?

The exact causes for the death of the dopamine-producing cells in the hypothalamus are still unclear. However, the entire metabolism can be supported with species-appropriate husbandry, little stress and a lot of exercise and thus prevent the possible development of Cushing's disease. When feeding, care should be taken to ensure that the amount of feed is adapted to the age and state of health of the animal, in order to avoid overweight and thus not to put further strain on the metabolism. Although this is no guarantee for a hundred percent prevention, it is nevertheless of utmost importance for keeping every horse healthy.

Which medication is used for Cushing's horses?

‍Thedrug Prascend (active ingredient: pergolide mesilate) is used to treat Cushing's horses. It reduces ACTH production and thus stabilizes the cortisol level.

How long can a Cushing's horse be put out to pasture?

‍Pasturegrazing should be restricted, especially on pastures with a high sugar content. A muzzle can reduce grass consumption so that sugar consumption remains controlled and the risk of laminitis is reduced.

What happens if Cushing's is not treated in horses?

‍UntreatedCushing's leads to serious secondary diseases such as laminitis, immune deficiency and long-term organ problems. This can drastically worsen the quality of life and shorten the horse's life.

When should a Cushing's horse be euthanized?

‍Avet should be consulted if serious complications such as laminitis or other complaints severely affect the horse's well-being. The decision depends on the horse's individual quality of life.

Can I breed with a Cushing's horse?

The Equine Cushing's syndrome can lead to fertility problems in mares, so that if a mare suffers from PPID is highly unlikely to become pregnant anyway. Furthermore, pregnancy means high physical and hormonal stress, which should be avoided at all costs in the case of hormonal disease. For the benefit of the horse horses with Cushing's disease should not be bred. Whether Cushing's disease in horses is hereditary in horses is difficult to say, as researchers disagree on what actually triggers Cushing's disease.

Is Cushing's fatal for my horse?

Not necessarily, as the disease itself is not fatal. However, if left untreated, it can lead to severe secondary diseases such as laminitis can result. If the coffin bone punctures through the sole of the hoof or the hoof is shod out, this means the end of the horse. Since PPID can be treated very well, there are Cushing's patients have a good chance of living a very good quality of life.