If you’ve ever noticed your older horse growing a shaggy coat that won’t shed, slowing down in their work, or developing recurrent hoof problems like laminitis, you might be looking at a condition called Pituitary Pars Intermedia Dysfunction—or PPID.

Previously known as “equine Cushing’s disease,” PPID is one of the most common endocrine disorders in horses over 15 years of age. It’s a chronic, progressive disease that can seriously affect a horse’s comfort, soundness, and quality of life if not recognised and treated appropriately. The good news? With the right diagnosis and management, many horses with PPID live active, happy lives well into their senior years.

Let’s break down what PPID is, how to recognise it, how we diagnose it, and what you can do to help your horse thrive.

What Is PPID?

PPID is a neurodegenerative condition that affects part of the horse’s pituitary gland—specifically the pars intermedia. As horses age, some develop damage to the nerves in the hypothalamus that regulate this gland. Without this control, the pituitary overproduces a hormone called ACTH (adrenocorticotropic hormone), leading to a cascade of hormonal imbalances throughout the body.

These hormonal shifts can impact metabolism, immune function, muscle condition, hair growth, and—critically—insulin regulation. About one-third of PPID horses also show signs of insulin dysregulation, which puts them at high risk for painful, life-limiting laminitis.

How Common Is It?

PPID is more common than many owners realise. According to the latest research, around 20% of horses over 15 and more than 30% of horses over 30 have PPID. While it’s typically a disease of older horses and ponies, early cases can occur in horses as young as 10.

What Are the Signs?

The most well-known sign of PPID is a long, curly hair coat that doesn’t shed properly—called hypertrichosis. However, PPID can present with a wide range of more subtle or less obvious signs, especially in early stages.

Early signs can include:

• Delayed or patchy shedding

• Mild topline muscle loss

• Decreased energy or performance

• Increased or decreased sweating

• Recurrent skin or respiratory infections

• Lethargy or change in behaviour

Advanced signs may include:

• Generalised hypertrichosis (long curly coat year-round)

• Muscle wasting and pot belly appearance

• Excessive drinking and urination

• Abnormal fat distribution

• Laminitis—often the first noticeable sign

Other possible signs:

• Infertility

• Chronic foot abscesses

• Slow healing wounds

• High worm burdens despite routine deworming

Importantly, recurrent laminitis in older horses is a major red flag. It often indicates that both PPID and insulin dysregulation (ID) are not being adequately controlled. Even mild elevations in insulin can trigger laminitis in susceptible horses, so testing and managing both conditions is essential.

How Do We Test for PPID?

PPID can’t be confirmed based on clinical signs alone. Diagnosis relies on blood testing to measure hormone levels—specifically ACTH.

There are two main approaches:

1. Baseline ACTH Test
   A single blood sample is taken, usually in the morning. This test is easy and accessible but must be interpreted with caution—ACTH levels can vary depending on time of year, breed, age, and stress levels (such as transport or pain).

2. TRH Stimulation Test
   Considered more sensitive, especially in early or borderline cases. TRH (thyrotropin-releasing hormone) is injected, and blood is taken 10 minutes later to see how ACTH responds. Horses with PPID show an exaggerated increase.

🧪 Timing and handling of blood samples is critical. Your vet will ensure that samples are kept chilled, processed promptly, and interpreted according to the latest seasonal reference ranges (Southern Hemisphere adjustments apply in Australia).

It’s also recommended to check insulin levels at the same time, as many PPID horses have concurrent insulin dysregulation.

Can Stress or Pain Affect the Results?

Yes. ACTH can rise in response to stress—trailering, excitement, or acute pain. Testing should ideally be delayed if the horse has just travelled or is visibly distressed. However, mild to moderate laminitis pain typically doesn’t invalidate the test.

Should I Treat Based on Test Results Alone?

Not always. We interpret hormone levels in the context of your horse’s age, clinical signs, breed, and season. For example, donkeys and ponies naturally have higher ACTH in autumn. In some cases, your vet may recommend retesting in 3–6 months rather than starting treatment right away.

In horses with classic signs—especially hypertrichosis—treatment can sometimes be started without testing at all, especially if access to diagnostics is limited.

How Is PPID Treated?

The mainstay of treatment is pergolide, a dopamine agonist that reduces ACTH production. It’s available in tablet form under the brand name Prascend®, and is usually given once daily.

Most horses start on 1 mg per day (or 2 µg/kg), with doses adjusted based on response. Some horses may show mild loss of appetite when starting pergolide, but this usually resolves within a few days.

🩺 Monitoring response is important. Your vet will likely recommend re-checking ACTH and clinical signs 1–3 months after starting treatment, and then every 6–12 months thereafter. Dose increases may be needed over time, or additional medications in refractory cases.

Important note on medication form:

We strongly recommend using the licensed Prascend® tablets, as these have been tested for stability, safety, and efficacy in horses. While liquid pergolide may be more convenient for some owners, pergolide is an inherently unstable compound and prone to degradation—especially when exposed to light or heat. This can result in inconsistent dosing and poor clinical response when using liquid preparation.

In certain cases, your vet may discuss the use of extended-release cabergoline, a longer-acting dopamine agonist. While this medication is not currently registered for use in horses, it has shown promise in some research and clinical cases. It may be an option for horses that don’t tolerate pergolide or require a different management approach. However, it is not suitable for all horses or ponies, and use should be discussed thoroughly with your veterinarian.

What Else Can I Do to Help My Horse?

PPID management isn’t just about pills. Holistic care makes a big difference in your horse’s comfort and longevity.

Key considerations:

• Regular hoof care – PPID horses are at increased risk of laminitis, even with controlled ACTH.

• Parasite control – Many PPID horses have reduced immune surveillance and higher worm burdens.

• Dentistry – Some lose condition due to dental issues, not just muscle wasting.

• Vaccination and infection monitoring – PPID horses may have impaired immune responses.

• Diet – Horses with normal insulin levels may do well on senior feeds and pasture. Those with insulin dysregulation need low NSC (sugar + starch) diets and restricted grazing.

• Exercise – Encouraged if the horse is sound. Exercise helps with weight control and insulin sensitivity.

Monthly monitoring of your horse’s body condition score (BCS) is also recommended to track changes over time.

Does Treatment Cure PPID?

No—PPID is a lifelong condition. But with proper treatment, many horses remain stable for years and continue to enjoy an excellent quality of life. Think of it like managing diabetes or arthritis—it’s not curable, but it’s very manageable.

When Should I Consider Testing My Horse?

You should speak to your vet about testing if your horse:

• Is over 15 years of age AND…

• Has any signs of delayed shedding, muscle loss, or lethargy

• Develops laminitis or recurrent infections

• Seems to be “aging rapidly” or declining in performance

Early diagnosis means earlier intervention—and better outcomes.

Take-Home Message

PPID is one of the most underdiagnosed and undertreated conditions in older horses. If caught early, it’s highly manageable. With a tailored approach—combining medication, nutrition, farriery, and wellness care—your horse can thrive well into their golden years.

If you’re concerned about PPID or want to learn more about testing and treatment, please contact us. At Avon Ridge Equine Veterinary Services, we offer comprehensive PPID consultations, tailored treatment plans, and ongoing support to help you manage your horse’s condition every step of the way.