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Equine Cushing’s Disease – Prevention, Diagnosis and TreatmentEquine Cushing’s Disease


By:  B.A. Long, Freelance Writer

 Pituitary Pars Intermedia Dysfunction (“PPID”), more commonly known as Equine Cushing’s Disease, is a disorder of the pituitary gland that knows no boundaries when it inflicts itself on horses or canines.  For purposes of this article, we will be referring to PPID in horses. While seemingly in the past it was thought to be a condition of older horses, as we will discuss in this article, present research indicates that age is not necessarily a contributing factor for your horse to develop this condition.  Tests are necessary, and sometimes are not conclusive, so typically it is not an easy disease to diagnose.  Regardless of how your horse is bred, the goal is always a healthy horse but this disease is complex and attacks with many symptoms which are not always easily recognizable to an untrained eye.In this article, we will address this endocrine disorder of the horse’s pituitary gland.  As stated, this disease typically is found in older horses, however, the disease has been diagnosed in horses as young as 8 years of age.  Since this disease is complex in its symptoms and treatment, the purpose here is not to attempt to substitute nor dispute any information that has alreadybeen addressed by your veterinarian.  Instead, we will discuss, in layman’s terms, preventative maintenance together with some helpful methods with which to treat horses affected with PPID. If you suspect your horse has exhibited suspicious symptoms, your first step should always be to ask your veterinarian or farrier.

Basically, in this disease the horse is suffering from a hormonal imbalance which causes many symptoms, which may include recurrent chronic laminitis, excessive sweating, lethargy, incessant thirst, and uneven shedding of hair to name some of the symptoms.  Various clinical symptoms are discussed and clearly stated in depth in an excerpt from an article below:

“Equine Cushing’s disease is a disorder of the pituitary gland that results in hormonal imbalances, causing a variety of clinical signs: a long, wavy haircoat that fails to shed according to normal seasonal patterns; excessive sweating; lethargy and poor athletic performance; chronic recurrent laminitis; infertility; weight loss; muscle wasting, especially along the topline; abnormal distribution of fat, with accumulations in the crest of the neck, tail head, sheath and above the eyes; consumption of large volumes of water and passage of large amounts of urine; delayed wound healing; and increased susceptibility to infections.

 The disease tends to occur in middle-aged and geriatric horses, with an average age of approximately 20 years at the time of diagnosis. Without treatment, symptoms tend to worsen over time and many horses are euthanized as a consequence of laminitis, recurrent foot abscesses or complications related to bacterial infections.

 What Causes Equine Cushing’s Disease?

 In dogs and humans, Cushing’s disease is caused by a hormone-secreting tumor of the anterior part (pars distalis) of the pituitary gland at the base of the brain. In horses, by contrast, the disease involves the intermediate part (pars intermedia) of the pituitary. This portion of the gland is comprised of different hormone-secreting cells than are present in the anterior pituitary, accounting for a different hormone profile observed in equine Cushing’s disease as compared to humans and dogs.”[1]

Recently, I went with a group of friends to the racetrack to watch harness racing.    As I sat and watched the most beautiful horses practice and then run the race proudly for their jockeys, I thought how wonderful to witness such trust between horse and human.  It’s clear that these were examples of horses which are the result of proper maintenance and health care addressing their each and every individual issue with the correct diagnosis and treatment.  Obviously, all horses are not bred for racing or competition but what all horses do share are health conditions and illnesses which have no boundaries in the equine world.  Whether your horse is living on a farm, training to race, preparing to show, all horses deserve and require attentive care suited for their individual health need.

While there is no cure, once diagnosed with the disease, proper maintenance of the horse will slow down the progress of this potentially fatal disease.   Once the horse is diagnosed with the disease, and before the symptoms progress, there are methods to care for your horse.  Set forth below are techniques to slow down the progression of the disease and maintain your horse after diagnosis:

  • An essential method of prevention is to protect the hoof of the horse.  Trimming the hooves of the horse as needed,on a regular basis, is necessary to prevent susceptibility and vulnerability to laminitis.
  • Faithful clipping of the hair is essential due to the uneven shedding associated with this disease.
  • Holistic or natural approach to healing as set forth below is easier for your horse and possibly will prevent the need for prescription medicine or, at the very least, decrease the required dosage.

“The goal in natural treatment of Cushing’s and Cushing’s-based laminitis is to provide nutritional support to prevent and reverse damage from circulating free radicals, prevent further damage to and encourage healthy laminar attachments and return the horse’s metabolism to proper balance. When managed correctly, with patience and attention to detail, most chronic cases can return to reasonable work. The poorly responsive cases can often be managed and kept relatively comfortable without the use of drugs.

 It is important to remember when treating laminitis with natural medicine to approach each case individually. It can be detrimental to any case to use multiple supplements or treatment modalities without carefully evaluating the case. Because a product is natural does not rule out harmful effects or the negative effects of using too many products and overloading the body. Refractory cases may require many products, however, they should not be used all at once.”[2]

In this article, we have been discussing the many warning symptoms and the complications that can stem before and after diagnosis.  Under the guidance of your veterinarian, you can adjust the treatment to your horse’s symptoms and level of disease.  As we stated at the beginning of the article, it is the goal of all involved in the care and treatment of the horse to do as much to prevent the disease and once diagnosed to set a program of treatment geared to the individual needs of your horse.  Proper assessment of your horse’s insulin sensitivity is essential before and after treatment for Equine Cushing’s Disease.  Further research to assess the insulin sensitivity in research was conducted by Amanda Adams PhD, Assistant Research Professor at University of Kentucky’s Gluck Equine Center as follows:

“Adams has an established herd of more than 40 aged horses, several of which she suspected had PPID. The researchers identified six horses affected by PPID based on conventional laboratory test results.

 Then they carefully selected six control horses (of the same age and sex as the PPID horses) that did not test positive for PPID and showed no clinical signs of PPID.

 “It was very important to us that the horses were age-matched, since that was the downfall of the previous studies,” Urschel explained. “Both the control and PPID horses in this study had an average age of about 25 years old.”

To quantify insulin sensitivity in these horses, the team used a technique called the euglycemic hyperinsulinemic clamp (EHC). The technique works by infusing insulin at a constant rate, and then adjusting the rate of glucose infusion to maintain the horse’s baseline plasma glucose concentrations. A higher rate of glucose infusion indicates a more insulin-sensitive horse, while a lower rate of glucose infusion indicates a less insulin-sensitive horse. Additionally, the researchers employed baseline plasma glucose and insulin values to calculate two proxies used to estimate insulin sensitivity and insulin secretory response in order to determine any differences between the two groups of aged horses.

 The researchers found that insulin sensitivity did not differ between the PPID horses and age-matched controls. The assessment of insulin sensitivity using the EHC procedure found no difference in glucose infusion rates between the two groups during the last 30 minutes of the EHC procedure. The two proxies used to measure insulin sensitivity and insulin response also showed no differences between PPID and aged controls. The only difference the researchers found between the two groups was a trend for the PPID horses to have higher glucose concentrations during the EHC procedure.[3]

 In an effort to control Equine Cushing’s Disease, Pergolide, a drug originally formulated to treat Parkinson’s disease in humans that was taken off the market in 2007, has been reformulated under the name of Prascend.   By letter to equine veterinarians in April of 2012, the U.S. Food & Drug Administration (“FDA”) advised veterinarians that Pergolide was now being sold under the name of Prascend.  Below is an excerpt from that letter:

“By prescribing FDA-approved PRASCEND, you provide your clients and their horses with the only marketed pergolide product shown to be safe and effective for controlling the clinical signs associated with Equine Cushing’s Disease. PRASCEND is also the only marketed pergolide product that is manufactured to meet FDA’s strict standards for quality, purity, and potency.

Please be aware that pergolide products should not be imported from other countries for use in animals. In addition, bulk pergolide should not be used to compound animal drugs.

A compounded animal drug is not FDA-approved. This means FDA has not evaluated the safety and effectiveness of the compounded drug or the adequacy of the manufacturing process.

After human pergolide products were removed from the market in May 2007, FDA exercised enforcement discretion by allowing, in appropriate circumstances, the compounding of the human product for use in horses. With the approval of PRASCEND, the conditions under which the agency previously exercised enforcement discretion no longer exist.[4]

            While the use of pergolide is often prescribed as a control drug for Equine Cushing’s Disease, an alternative is the use of chasteberry, an herb which helps balance the pituitary and hypothalamus glands while providing the necessary requirement of Vitamin C for your horse… a common deficiency in horses diagnosed with Equine Cushing’s Disease.

In conclusion, the bottom line is to keep the horse as comfortable as possible while taking the correct steps necessary by treating each horse on a case-by-case basis with the best treatment available for your horse. Do not be afraid to ask any question of your veterinarian or farrier because every horse diagnosed with Equine Cushing’s Disease does not exhibit the same symptoms.  The relationship between the horse and human is one of trust.  Your realization that you have accomplished all that can be done to care for your horse will provide peace to you as the owner or caretaker and comfort to your horse.  Although there is no known cure for Equine Cushing’s Disease, to coin a phrase from an old adage…may you and your horse experience the healthiest and happiest of trails!

[1]“Equine Endocrinology: Cushing’s Disease and Metabolic Syndrome” By Christie Malazdrewich, DVM, Diplomate ACVIM; University of Minnesota College of Veterinary Medicine  – Endocrine Diseases – Jan 5th, 05

[2]Nutritional Treatment of Equine Cushing’s Disease and Laminitis

Joyce C. Harman DVM, MRCVS
Madalyn Ward DVM

[3]Insulin Resistance: Not Just for Old Cushing’s Horses

  By University of Kentucky College of Agriculture

[4]FDA. PRASCEND (pergolide mesylate) Tablets – Veterinarians, April 20, 2012