Understanding PPID

Key Message

Pituitary Pars Intermedia Dysfunction, or PPID, is a progressive disorder of the pituitary gland that becomes more common as horses age.

It affects the way certain hormones are controlled, and one of its most serious consequences is an increased risk of laminitis, particularly when PPID is also associated with high insulin. PPID is not the same as Equine Metabolic Syndrome, although a horse can have both.

The good news is that PPID can often be managed very successfully with appropriate medication, monitoring and, where needed, diet and insulin control.

 

At a Glance

• PPID was previously called equine Cushing's disease.
• It is caused by changes in the brain and pituitary gland that reduce normal dopamine control.
• PPID becomes more common with age, but early cases may appear before the classic long curly coat develops.
• Laminitis can be one of the first signs.
• Other early signs may include subtle shedding changes, loss of topline, tendon or ligament problems, increased drinking or urination, new allergies, recurrent infections and unexplained changes in body condition.
• PPID and EMS are separate conditions, but they may occur together.
• ACTH blood testing is central to diagnosis, but results need to be interpreted in context because season, stress, pain, transport, sample handling and laboratory method can affect the result.
• Some early PPID horses may have normal ACTH results.
• Pergolide is the main treatment. Cabergoline is an alternative in some cases.
• PPID usually requires lifelong management.
• If the horse also has high insulin, diet and exercise management are still essential.

 

The Full Lesson 

What is PPID?

PPID stands for Pituitary Pars Intermedia Dysfunction.

It was historically called equine Cushing's disease, but PPID is the more accurate name because the disease in horses is different from Cushing's disease in people and dogs.

The pituitary gland sits at the base of the brain and helps control many hormones in the body.

Within the pituitary is a section called the pars intermedia.

In a healthy horse, this part of the pituitary is kept under control by dopamine, a chemical messenger produced by nerves in the brain.

In horses with PPID, those dopamine producing nerves gradually deteriorate. With less dopamine available, the pars intermedia becomes overactive and produces excessive amounts of several hormones.

That hormonal disruption is what produces the signs we recognise as PPID.

 

Is PPID a tumour?

You may sometimes hear PPID described as a pituitary tumour.

That is not completely wrong, but it is a little too simple.

The pars intermedia often becomes enlarged and may develop areas of hyperplasia or benign adenoma formation. However, the underlying problem appears to begin with progressive loss of dopamine producing neurons in the brain.

So it is better to think of PPID as a progressive neuroendocrine disease, involving both the brain and the pituitary gland.

You do not need to understand all of that biology to manage your horse.

The important point is that the pituitary is no longer being regulated normally, and medication is used to replace some of that lost dopamine effect.

 

PPID is not the same as EMS

PPID and Equine Metabolic Syndrome are different conditions. EMS is primarily associated with high insulin and insulin resistance. PPID is a progressive disorder involving the pituitary gland.

However, the two can occur together, especially in older horses.

That is important because:
• PPID generally requires medication.
• EMS requires diet and exercise management.
• A horse with both conditions needs both parts of the problem addressed.

 

What are the signs of PPID?

The classic sign most people recognise is a long, curly coat that does not shed normally. But that is usually a later sign. Earlier PPID can be much more subtle.

Possible signs include:
• Delayed or incomplete shedding
• A slightly longer or heavier coat than usual
• Loss of topline muscle
• A pot bellied appearance
• Weight loss despite a good appetite
• Increased drinking
• Increased urination
• Recurrent infections
• Poor wound healing
• New or worsening allergies
• Increased sweating or reduced ability to sweat normally
• Unexplained tendon or ligament problems
• Recurrent or seasonal laminitis
• Development of regional fat deposits or high insulin later in life

One of the most important things to understand is that laminitis may occur before the classic coat changes appear.

That is why unexplained laminitis in an older horse should always raise suspicion of PPID.

 

Above - the long curly coat typical of a horse with PPID.

 

Above - An advanced PPID and chronic Laminitis case - this pony was completely rehabilitated by Victorian Trimmer Sandi Chiswell.

Why does PPID increase laminitis risk?

PPID does not automatically cause laminitis in every horse.

The greatest risk appears to occur when PPID is also associated with high insulin. Some horses with PPID develop worsening insulin resistance and hyperinsulinaemia. When insulin becomes too high, the horse becomes vulnerable to hyperinsulinaemia associated laminitis.

This is why a horse diagnosed with PPID should not only have ACTH considered.

Insulin may also need to be tested and managed.

If insulin is high, controlling PPID with medication alone may not be enough. Diet, pasture and exercise management may also be necessary.

How is PPID treated?

The main treatment for PPID is pergolide.

Pergolide is a dopamine agonist, which means it acts like dopamine at the pituitary and helps restore some of the control that has been lost.

The active ingredient in Prascend is pergolide mesylate.

Cabergoline is another dopamine agonist and may be considered where pergolide is not suitable or does not provide adequate control.

The aim is to control the individual horse's clinical signs and hormone levels.

Is there a standard pergolide dose?

There are standard starting recommendations, but horses vary considerably in the dose they require.

The ECIR approach is that the appropriate dose is the dose that adequately controls the horse's PPID, including through the seasonal rise. Some horses remain well controlled on relatively low doses. Others require higher doses or seasonal adjustments which is why follow up testing and monitoring matter.

 

What about Chaste Tree Berry?

Chaste Tree Berry, also called Vitex agnus castus, may improve some clinical signs in certain horses.

However, the ECIR material is clear that it does not reliably control the underlying PPID or ACTH production. It should not be considered a replacement for pergolide or cabergoline where medication is required.

Does a horse stay on medication for life?

PPID is generally considered a progressive, lifelong condition. Once diagnosed, the horse will usually require ongoing medication and monitoring.

That can sound worrying, but many horses do very well for years when treatment is tailored appropriately. The goal is not to cure PPID but to control it well enough that the horse remains comfortable, metabolically stable and free from preventable complications such as laminitis.

If the horse has high insulin as well as PPID, then diet, pasture access and exercise become just as important as medication.

The most important thing to remember:

PPID is a progressive hormonal disease that often starts quietly. Early signs may be subtle. Laminitis may be one of the first clues.

A normal ACTH result does not always completely rule out early disease, particularly when the history and clinical signs remain suspicious.

The most effective management combines:
• Careful diagnosis
• Appropriate medication
• Monitoring through the seasons
• Insulin control where needed
• Appropriate diet and exercise

With good management, many PPID horses can remain comfortable and active for many years.

 

Further Reading

This lesson has been prepared primarily from the following resources.

ECIR Group
• Pituitary Pars Intermedia Dysfunction, ECIR educational material.
• Frequently Asked Questions: Pituitary Pars Intermedia Dysfunction.
• Diagnosis + Diet/Drugs + Trim + Exercise, DDT+E Protocol.

NO Laminitis! Conference Proceedings
• Eleanor M. Kellon, VMD, Little Recognized Signs of Early PPID, 2025 NO Laminitis! Conference.
• Jo Ireland, BVMS PhD CertAVP(EM) FHEA FRCVS, Factors Affecting ACTH Concentration and Implications for Diagnostic Testing, 2025 NO Laminitis! Conference.
• Eleanor M. Kellon, VMD, Pergolide Dosage and Other ECIR Poll Results, 2025 NO Laminitis! Conference.
• Harold C. Schott II, DVM, PhD, DACVIM, Is PPID Parkinson's Disease of Equids?, 2025 NO Laminitis! Conference.