Cushing’s disease in horses, also known as pituitary PARS Intermedia Dysfunction (PPID), is the most common endocrine disorder diagnosed in horses.
Key takeout
- Cushing’s disease is a progressive disorder in horses that affect the pituitary gland.
- Cushing in horses ultimately causes the adrenal glands to produce more cortisol.
- A horse with Cushing’s disease may have underlying conditions such as the horse metabolic syndrome.
- Treatment of Cushing’s disease in horses is an FDA approved tablet called Prascend® (Pergolide).
What is Cushing’s Disease in Horse?
Cushing’s disease in horses is a progressive disorder of the pituitary gland and is part of the endocrine system that plays an important role in hormone production and regulation. Dysfunction of the endocrine system can have a negative effect on the entire horse’s body, leading to immune and reproductive system malfunction, insufficient coat, weight issues, and other symptoms discussed below.
Cushing’s disease in horses Similar disorders affecting dogs and people can affect horse versions of different aspects of the pituitary gland. In dogs, Cushing’s disease is due to the abundant production of cortisol (stress hormone) by the adrenal glands just above the kidneys.
How Cushing’s Disease affects horses
In horses, Cushing’s disease is usually seen when neurons in the hypothalamus of the brain that produce dopamine are degenerated.
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Dopamine acts as a chemical messenger and instructs other glands to increase or decrease the production of other hormones.
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When dopamine decreases, the intermediate PARS portion of the pituitary gland becomes overactive, producing excess adrenocortical cortical hormones (ACTH), growing like benign (non-cancerous) tumors.
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Higher levels of ACTH direct the adrenal glands to increase the production of hormones such as cortisol.
All horse breeds can be diagnosed with Cushing’s disease in horses, but pony and Morgan breeds can be predisposed.
Symptoms of horse cushioning
Cushing’s disease is a progressive disorder. Symptoms may be present slowly, but they progress over time.
What are the first signs of Cushing’s disease in horses?
Symptom development may vary from horse to horse. Not all horses with PPIDs experience all or even most of these symptoms. Some of the most common signs observed in horses with Cushing’s disease include:
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Unable to completely drain a winter coat or patchy fall off
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Long and/or curly coat
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Changes in behavior
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Stomatitis or multiple laminitis episodes
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Hoove abscess or recurrent hoove abscess
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Infertility or lack of normal estrus cycle in mares
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Lethargic
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Weight loss
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Fat accumulation in abnormal areas
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Loss of the top line
Late stages of horse cushioning
While some “common” early symptoms can also occur in individual horse diseases, typical progressive symptoms of Cushing are:
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More pronounced loss of muscle mass (especially the back and posterior quarter)
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“Potberry” exterior
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Increased water intake and urination
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Excessive or inappropriate sweating
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Repeated or chronic infection
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Abnormal breast development
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Suspension ligament degeneration
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Recurrent cornea (eye) ulcer
What causes Cushing’s disease in horses?
Cushing’s disease in horses is a degenerative disease of the hypothalamus. The hypothalamus is the structure of the brain that regulates hormone production through communication with the pituitary gland.
In healthy horses, the endocrine system is a balanced network of structures and organs that work together in a series of feedback loops, producing and regulating hormone levels throughout the body.
In PPID horses, loss of hypothalamic function leads to problems with the pituitary gland called PARS Intermedia (PI).
Cushing’s disease is a progressive disorder. Symptoms may be slow to exist, but they will eventually progress over time.
The pituitary gland usually produces hormones that help regulate normal body functions. Equine Cushing’s disease occurs when abnormal growth (benign tumors) occurs in the PI area of the pituitary gland.
As the tumor grows, the PI expands. This increases the production of a hormone called adrenal cortical hormone (ACTH), which stimulates the adrenal glands to produce more hormone called cortisol.
Cortisol is known as a “stress hormone” and controls many important physical functions, such as blood glucose levels. Excessive and consistent levels of cortisol can lead to horse problems, including increased susceptibility to infection, insulin resistance, steatitis, and muscle waste.
Diagnosis of Cushing’s Disease in Horse
Veterinarians diagnose Cushing’s disease in horses through a combination of horse history, physical examinations and diagnostic tests.
There are two main diagnostic tests for PPID. Baseline plasma ACTH concentration and thyroid stimulating hormone (TRH) stimulation test.
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Baseline ACTH Test A simple blood sample sent by a veterinarian to the lab.
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TRH stimulation test It is also a blood sample, but two blood draws are required. This is the baseline sample and the second sample taken after an intravenous administration of a hormone called thyroid stimulation to the horse. The second blood sample is collected 10 minutes after thyroid stimulant injection. Then, both samples are sent to the lab to compare their respective ACTH levels.
For early symptoms of horse cushioning, a TRH stimulation test is recommended as the first test. Baseline ACTH levels can be incorrectly negative at the early stages of the failure.
In horses with late stages of PPID, or with many symptoms, testing of baseline plasma ACTH levels may be sufficient to make a diagnosis. Your vet may request your horse to fast for 12 hours before blood is drawn.
Other tests recommended for veterinarians include dexamethasone suppression tests and magnetic resonance imaging (MRI) specific to PI expansion.
Treatment of horse Cushing’s disease
There is no treatment for PPID, but daily medications can be administered to deal with symptoms of the disease.
First-line treatment for Cushing’s disease in horses is FDA approved tablets Prascend® (Pergolide). Prascend® functions like synthetic dopamine and improves the regulation of ACTH production in PARS Intermedia.
Some horses may need to gradually start Prascend®.
Management of horse cushion medicines
Veterinarians may recommend retesting ACTH levels in horses when the medication is administered for 1-3 months and then every 6-12 months.
Routine blood test monitoring is important to ensure that Prascend® doses are effective and that the disease is not exacerbated. Some horses may require slightly higher doses over time as the disease progresses.
Recovery and management of Cushing’s disease in horses
It is important that the horse is diagnosed with PPID and is started with Prascend®, and then administered a medication prescribed to assist in regulating ACTH levels. Swing levels can lead to recurrence symptoms.
Approximately a third of horses with PPID suffer Because it is the equine metabolic syndrome (EMS), if your horse is suffering from both, you may need low-sugar diet, diet or exercise management, or other medications, as directed by your veterinarian.
Give the horse a cushion
Cushing’s illness does not approach equality for all horses. In general, horses with PPIDs must have certain low, nonstructural carbohydrate feed or distribution balancers that provide all the essential nutrients that the horse needs with minimal calories, as they have underlying conditions such as the horse metabolic syndrome or are sensitive to starch.
Choosing a suitable diet for horses with PPID and/or EMS should always be done with your veterinarian. Your horse may need high fat, carbohydrate, or protein content in your feed, depending on whether you are suffering from weight loss or gain, and whether there are other metabolic concerns.
Horse that are prone to or prone to insulin resistance and EMS may require strictly forged diets or grasses with ration balancers replenished.
Some feeds that may be good choices for horses that benefit from a low NSC diet include:
Other senior horses struggling to maintain weight may require a balanced senior feed, higher calorie feed, or fat supplement without adding carbs.
Equines with PPID often suffer from impaired immune function, so supplementation with omega or antioxidants is also beneficial. Amino acids can also help with loss of topline.
Cushing’s disease and not feeding horses
Horses with Cushing’s disease should not normally be given a diet containing sugar. The grain must contain less than 10% sugar and starch, and it may be necessary to analyze the horse’s hay. If the analysis of hay sugar and starch levels returns high, you will need to replace the feed or soak the hay.
Limiting grass intake is also recommended, especially in spring and autumn when grass sugar is at its highest level.
Management of other symptoms of horse Cushing syndrome
In addition to treating Prascend® for PPID in horses, which often have an immune system, routine wellness care is important to minimize the likelihood of steatitis, coli pain, infection, foot abscesses, and other developments. This includes:
Many horses with Cushing’s disease have a hard time removing their winter coat. As temperatures rise, it can help the horse feel more comfortable Body clipping.
Cushing’s Disease in Horse FAQ
How long do horses live with Cushing’s disease?
Symptoms of Cushing’s disease in horses often occur around 15 years or more. Medical management improves the quality of life. It does not necessarily extend your lifespan, but depends on the overall health of your horse. Secondary conditions that often occur with PPIDs, such as repetitive or severe laminitis and infection, can lead to systemic disease and early passage.
What are the first signs of Cushing’s disease in horses?
Generally, the first clinical signs of Cushing’s disease are long or delayed fallout, abnormal fat deposits, loss of top-line muscle, or weight loss and dylitis.
Do you have Cushing’s disease at the horse terminal?
Although horses cannot recover from Cushing’s disease, they can manage their condition, and horses can live a high quality life with effective treatment.
What happens if Cushing is left unprocessed by the horse?
The untreated Cushing’s disease continues to progress, causing the horse’s weakened immune system to deteriorate. Secondary conditions such as laminitis may occur. Repeated or systemic infections can cause other serious complications and poor quality of life.
Are there any natural treatments for Cushing’s disease in horses?
While natural treatments do not cure Cushing’s disease or resolve symptoms completely, some alternatives to PPID may be discussed with the veterinarian. Chaste Tree Berry (Monk’s Pepper) is used in some horses with PPID because of their immune stimulating properties. Adjuvant therapies, such as chiropractic and acupuncture, can also support the body’s healthy immune function and hormonal and neurological balance.
