Last Updated on December 25, 2021 by Urska
Cushing’s disease in horses, words a horse owner never wants to hear their veterinarian say. In my 29 years as a horse owner, I have lost two of my favorite horses to Cushing’s, the first being my very first pony, Pepper, and 15 years later my show horse, Samantha.
So that being said, what then is Cushing’s in horses? What are the symptoms? Can this devastating disease be prevented? Unfortunately, there are no easy answers to those questions. However, being able to recognize the early signs and symptoms of a horse with Cushing’s will help you and your horse.
What Is Cushing’s in Horses?
Cushing’s Disease also known as Pars Intermedia Dysfunction (PPID) occurs not only in horses but also in dogs and humans as well. Across all species, the same brain structure, the pituitary gland, is effected.
However, unlike dogs and humans where a tumor affects the pars distalis (the posterior part of the pituitary), Cushing’s Disease in horses targets pars intermedia (or the middle part) of the pituitary gland. And due to the difference in the targeted areas, the pituitary secretes different hormones based on the location of the tumor. Therefore, Cushing’s Disease in horses secretes different hormones than Cushing’s that are found in dogs and humans.
As a result of the tumor and its location, in horses, the pars intermedia over secretes pro-opiomelanocortin (POMC), adrenocorticotropic hormone (ACTH) and several other hormones like them. In a healthy horse, the function of the pars intermedia is regulated by the hypothalamus which is responsible for a lot of your horses’ bodily functions, like thirst, hunger, body temperature, and blood pressure.
The POMC then creates cortisol, a hormone that regulates your horse’s blood sugar, stress, and inflammation, while the adrenocorticotropic hormone (ACTH) is charged with the regulation of the levels of cortisol that are released into your horse’s body. You can read more about equine endocrinology, the brain structures affected in Cushing’s Disease, and the hormones secreted here.
Signs & Causes of Cushing’s Disease in Horses
Unless you can control the internal workings of your horse’s body, there is no way to prevent Cushing’s Disease since it is caused by a tumor, that grows on your horse’s pituitary gland. However, it is important to know that some steroids used over a long period of time to treat other conditions your horse may have, can increase their risk of Cushing’s Disease. Thus, before deciding to use steroids long term, it is very important to talk with your veterinarian, so as to know how long the steroids will be prescribed and if you’ll have any other treatment options for your four-legged friend.
So how do you know whether or not your horse is living with Cushing’s Disease? Simple. You will notice some changes to their behavior that can be linked back to the bodily regulatory functions of the pars intermedia and the hypothalamus, increased thirst, subsequent increased urination, increased hunger, excessive sweating, and fatigue.
You may also notice some changes in your horse’s body, such as a wavy coat. It is a coat that does not shed when seasonally appropriate, muscle atrophy and chronic laminitis or foundering. You can read more about the clinical signs of Cushing’s Disease here.
Treatment of Cushing’s in Horses
If you notice any sign of Cushing’s Disease in your horse, you have to promptly contact your veterinarian. They will do an evaluation of your horse’s condition and may request a blood test to check the sugar and fat levels in your horse’s blood. This, in combination with the physical evaluation, will help your vet distinguish between Cushing’s Disease and Equine Metabolic Syndrome, which often presents in a similar fashion to Cushing’s with a few distinguishing factors.
Once Cushing’s has been diagnosed, there will be many therapies available to you in addition to “supportive care” which will include monitoring your horse and treating any symptoms that may arise as a result of the Cushing’s such as laminitis.
Your vet may prescribe your horse a couple of medications based on their evaluation of your horse. The first is Pergolide, a dopamine receptor that will help your horse’s body manage its overactive pituitary gland.
The second is Cyproheptadine, an anti-inflammatory that will block histamine production. The inability to regulate inflammation is a direct result of the tumor on your horse’s pituitary. Thus, this drug will assist your horse in combating unnecessary inflammation.
Always discuss pharmaceutical options with your vet to ensure that the drugs prescribed by your veterinarian are quality drugs, that contain the active ingredients needed to treat Cushing’s. Beware, even though you may find cheaper versions of these drugs from pharmacies on the internet, however, the effect will succinctly tell on your horse, who without quality medication, will suffer in the long run.
Thus, always be sure to use a reputable pharmacy.
One of the most important treatment options for Cushing’s disease in horses is Supportive Care. The purpose of supportive care is to increase your horse’s quality of life. It is extremely important for the longevity of your horse, that you ensure that you are feeding your horse a diet that is right for them. The University of Florida suggests limiting carbohydrates because your horse cannot properly metabolize glucose that is created from these foods by their bodies, as a result of Cushing’s Disease.
They also suggest that feeding a grain that was formulated for older horses will be most helpful. Because they are much more likely to contain fewer carbohydrates. Carbohydrates can also be found in your horses’ hay. Your vet may suggest that you feed them with low-carb hay, which can be pretty mind-boggling. Here is a great link for understanding what to look for when shopping for low carb hay.
In addition to diet, you are going to want to treat any symptoms that your horse may display. Doing it quickly as a result of Cushing’s Disease. And this can include abscesses or chronic laminitis. You can also support your horse seasonally by helping him shed his winter coat. Do this in the spring through brushing or blanketing him in the winter months when it’s cold.
Cushing’s Disease, if gone unnoticed or not properly treated, can be devastating to your horse’s health. Nevertheless, there are still many horses with Cushing’s that live full. And quality lives all thanks to the diligence of their owners.
Proper treatment will not only restore fertility in the prized broodmares of the horse but will also make it ridable. It’s very rare for a horse to reach full remission from Cushing’s. A horse whose symptoms are well managed can be regularly ridden. But that is a choice that varies by the owner. Also, the ability to be ridden again is a discussion you should explore with your veterinarian.
Even if it is concluded that it is safe to ride your horse, you should be on the lookout for overheating and laminitis. A horse with sore hooves should never be ridden. And the inability to regulate body temperature is a symptom of Cushing’s Disease. If you have any questions or comments regarding Cushing’s Disease, please feel free to comment below.
- Cushing’s Disease is also referred to as Pars Intermedia Dysfunction (PPID) with an average onset of 20 years of age.
- Symptoms of Cushing’s Disease include a wavy coat that does not shed, bulgy-eyes, and chronic laminitis. Also, increased thirst, increased urination, and increased appetite.
- Treatments for Cushing’s Disease include medication therapy and supportive care.
- Low Carbohydrate and Low Sugar diets are recommended.
- Be sure to use a quality, reputable pharmacy for any medications prescribed to treat your horse’s condition.
- A horse with Cushing’s Disease can still live a quality life. While the likelihood of remission is low, proper management of symptoms can help. It can increase the chances that your horse will be rideable again.
What are the first signs of Cushing's disease in horses?
In most cases, Cushing's disease begins as subtle changes in behaviour and appearance. The most obvious sign is the lack of a topline. The hair coat may be thin or coarse, and there may be evidence of delayed shedding. Horses with Cushing's disease are usually lethargic. Their appetite and energy levels decrease. They may become reluctant to work and show signs of decreased athletic performance. Affected horses can also suffer from laminitis and infertility.
What is the most common cause of Cushing's syndrome?
The most common cause of Cushing's syndrome in horses is a noncancerous tumor of the adrenal cortex, called an adrenal adenoma. This type of tumor grows slowly and is usually discovered when the horse has a routine physical examination. In some cases, however, the tumor may be missed completely until the horse is examined for another reason.
Cancerous tumors of the adrenal cortex don't develop that often, but if they do, they can also cause Cushing syndrome. These tumors grow much more quickly and are usually found when the horse has symptoms such as weight loss, weakness, depression, diarrhea, fever and other signs of illness. Sometimes, a cancerous tumor will invade nearby tissues or spread to other organs.
Can a horse recover from Cushing's?
Cushing's syndrome can not be cured but the disease can be quite well managed with medication and changes to the horse's diet.
The outlook for a horse with Cushing's depends on a number of factors. These include: the size and location of the tumor, whether or not the tumor is cancerous, how old the horse is when diagnosed, the general health and condition of the horse before the onset of the disease.
It is important for you to understand the signs and symptoms of Cushing's so you can recognize it early in its development and seek veterinary advice immediately.
Should you ride a horse with Cushings?
Before starting an exercise or riding program, you should always check with your veterinary. If the Cushing's syndrome is well controlled, horses with the condition can be ridden like any other horse. There are some things to consider, though. Delay in shedding winter coat can contribute to overheating. You also need to pay attention to signs of laminitis and blindness that can be caused by Cushing's syndrome. If your horse is experiencing any of the above mentioned issues, you can only ride him in a safe environment and under controlled conditions (in the shade, on the smooth surfaces,...).
What is the difference between Cushing's syndrome and Cushing's disease?
Cushing disease is a specific type of Cushing syndrome, caused by a pituitary tumor. Pituitary tumor affacts the body in a way that it produces too much cortisol. The symptoms can be mild or severe and may include tiredness, weight gain, and diabetes. If left untreated, Cushing disease can lead to serious complications including heart disease, diabetes, osteoporosis, and depression.
Cushing disease is the most common form of endogenous (from the body) Cushing syndrome, and makes up about 70% of Cushing syndrome cases. The other 30% of cases are due to exogenous causes, which includes adrenal tumors (adenomas and carcinomas), pituitary tumors (prolactinomas, somatotropinomas, or growth hormone-secreting adenomas), ectopic adrenocorticotropic hormone (ACTH) secreting tumors, and ACTH-producing tumors of extra-pituitary origin.