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Equine Cushing's Disease: Part I
Equine Cushing’s Disease, also called Pituitary Pars Intermedia Dysfunction (PPID), is one of the most common hormonal disorders affecting horses and ponies. It is seen most often in older horses, but it can occur at any age. Understanding PPID is essential for early diagnosis, effective management, and preventing serious complications like laminitis.
This guide explains what Equine Cushing’s Disease is, how to recognize the signs, how it’s diagnosed, and how it’s managed—in plain language for horse owners.
What Is Equine Cushing’s Disease (PPID)?
Equine Cushing’s Disease is caused by a dysfunction of the pituitary gland, a small gland located at the base of the brain. The pituitary controls many important body functions, including:
- Hormone production
- Metabolism
- Immune function
- Stress response
In horses with PPID, the pituitary gland produces excess hormones, especially ACTH, which leads to increased cortisol levels. Over time, this hormonal imbalance affects nearly every system in the body and can significantly impact a horse’s health and comfort.
What Causes Equine Cushing’s Disease?
The exact cause of PPID is not fully understood, but it is linked to changes in how the brain regulates the pituitary gland, specifically within the hypothalamic-pituitary-adrenal (HPA) axis.
Several factors may increase a horse’s risk, including:
- Advancing age
- Genetic predisposition
- Environmental influences
- Breed susceptibility, with ponies, Morgans, and some smaller breeds appearing more prone
Signs and Symptoms of Equine Cushing’s Disease
Early detection is key. Some horses show subtle signs at first, while others develop obvious symptoms as the disease progresses.
Common Symptoms of PPID Include:
- Long, thick, or curly hair coat that does not shed normally
- Excessive sweating, especially under heavy hair
- Increased drinking and urination
- Muscle loss, especially along the topline
- Lethargy and decreased performance
- Pot-bellied appearance
- Recurrent infections, such as hoof abscesses or respiratory issues
Laminitis and PPID
Laminitis is the most serious and potentially devastating complication of Equine Cushing’s Disease. Persistently elevated ACTH levels have a toxic effect on the laminae of the hoof, significantly increasing the risk of painful and recurrent laminitis episodes.
How Is Equine Cushing’s Disease Diagnosed?
Diagnosis is based on a combination of clinical signs and blood testing.
Common Diagnostic Tests:
- ACTH Blood Test: Measures adrenocorticotropic hormone levels, which are often elevated in horses with PPID.
- TRH Stimulation Test: A more sensitive and specific test that can detect early or subclinical PPID, even before obvious symptoms appear.
Your veterinarian will recommend the most appropriate test based on your horse’s age, symptoms, and time of year.
Managing Equine Cushing’s Disease
While there is no cure for PPID, proper management allows many horses to live long, comfortable, and active lives.
1. Medication
- Prascend® (Pergolide) is the cornerstone of treatment.
- Pergolide is a dopamine agonist that helps regulate hormone production and reduce clinical signs.
- Dosage is adjusted based on symptoms and follow-up testing.
2. Diet Management
- Feed a low-sugar, low-starch diet
- Avoid high-carbohydrate feeds
- Proper nutrition helps reduce insulin resistance and lowers laminitis risk
3. Exercise
- Regular, appropriate exercise helps maintain muscle mass and overall health
- Exercise plans should be tailored to the horse’s age and soundness
4. Ongoing Veterinary Care
- Routine monitoring of ACTH levels
- Regular dental, hoof, and general wellness care
- Most veterinarians recommend ACTH testing at least once yearly, or more often if medication adjustments are needed
Living Well With Equine Cushing’s Disease
Equine Cushing’s Disease can feel overwhelming at first, but with early diagnosis, consistent treatment, and close veterinary partnership, affected horses can enjoy an excellent quality of life.
By learning to recognize the signs of PPID and staying proactive with management, horse owners play a vital role in protecting their horses from complications—especially laminitis—and supporting long-term health and comfort.
If you suspect your horse may have PPID or want to discuss testing options, consult your veterinarian to develop a personalized care plan.
This article was written by the veterinarians at North Bridge Equine Associates, an ambulatory equine veterinary practice serving horses in Massachusetts and surrounding regions. The information provided is intended for general educational purposes and is not a substitute for veterinary examination or care.
North Bridge Equine Associates
978-337-1260
Servicing Massachusetts, New Hampshire, and seasonal service to Aiken, South Carolina
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