Content

1. What PPID actually is
2. Why PPID diagnoses have exploded
3. My Cushing's world
4. The hormonal chain reaction - what’s really driving those changes
5. And so begins the metabolic effect
6. Prascend (Pergolide)
   
7. Natural plant therapy
8. Top Tips
9. Steps to lower cortisol and stimulate dopamine levels naturally
10. Updates

Principal Body System: Endocrine

Definition: All glands that produce hormones.

Function: Regulates body activities through hormones transported by the cardiovascular system.

Cushing’s – or more accurately Pituitary Pars Intermedia Dysfunction (PPID) – gets thrown around so much these days that it can feel like half the horse world is diagnosed with it. For sure it’s real, but it's also far more nuanced than a number on a blood test - and far more individual than the "one size fits all" advice most owners hear.



Put simply, it's a hormone imbalance that happens when the pituitary gland stops working properly. Instead of sending the right messages, it floods the body with stress hormones (cortisol, adrenaline) while dopamine naturally declines with age. The result? A tired-but-wired horse who can slide into lethargy, insulin resistance, laminitis risk, and a host of knock-on issues.

This page is here not to diagnose or prescribe – but to help you understand what’s happening behind the scenes, so you can feel more confident and informed when speaking with your vet – and more connected to what your horse may be trying to tell you. It's here to explain what PPID actually is, what’s going on inside your horse’s body, and why so many owners end up confused, overwhelmed, or signing up for lifelong medication before anyone has even looked at the big picture. 

What PPID actually is (the real version)

“If you think about what our biology needs to do, it has to deliver the right chemicals and hormones, in the right concentrations, to the right tissues and organs, at the right time of day, to be able to function,”

Prof. Russell Foster, Professor of Circadian Neuroscience at Oxford University

Here’s the part most horse owners don't know: PPID doesn’t start in the pituitary gland. It starts in the brain.

Specifically, it starts in the hypothalamus, where tiny dopamine-producing neurons live. These neurons normally act like a brake pedal on the pituitary, but as horses age – and some more than others – those neurons begin to decline.

When the “dopamine brakes” wear out:

• the pituitary ramps up
• ACTH increases
• hormone signals get messy
• the horse’s whole internal rhythm shifts

This can show up as:

• delayed or patchy coat shedding
• changes in thirst or wee output
• mood/energy dips
• stress sensitivity
• odd fat pads or cresty bits
• immune wobbliness
• occasional hoof sensitivity

Here’s the key - this decline happens slowly, it varies hugely between horses, and it’s not something we caused. It’s simply physiology – not owner error.

Why PPID diagnoses have exploded

Short answer?  Because we’re testing everything that moves.

Until the 1980s, PPID was considered a rare disorder found mostly in elderly horses. Today? Depending on the region and testing promotions, it can feel like half the yard carries the label – including surprisingly young horses.

This doesn’t necessarily mean PPID has suddenly exploded. What’s actually happened is that :

• Testing has increased massively – at the very times that ACTH levels naturally rise, i.e. spring and autumn
• Targeted seasonal-screening campaigns for the drug Prascend have been strong – that alleged “free” test is attractive (you'll still have to pay for the visit though)
• Many owners are given false positive results
• ACTH also rises from stress / vet visits / pain / herd drama / someone sneezed wrong…

In other words - we’re looking a whole lot sooner than we used to. It doesn’t invalidate the diagnosis, but it does mean context is essential. It doesn’t mean the condition suddenly became widespread - put simply, it means we’re looking more at the exact times ACTH naturally spikes, in horses who may or may not be symptomatic.

Context matters - a lot.  ACTH testing is helpful, but it's not a standalone diagnostic. So if your horse scores high in spring or autumn just after the farrier, a rainy week, or a yard reshuffle… take a breath. A single number doesn’t define your horse, because ACTH rises when dopamine neurons decline – but also when the horse has simply had A Day.

Understanding this helps owners stop spiralling and start thinking clearly.

 

My PPID world

My own experience with Cushing's first came out of the blue many years ago with my step-daughter, Tabatha's, first pony, Dinky.

We'd not long had Dinks - just 6-weeks; he was a lovely senior chap, around 20yo, standing proudly at 12.2hh, and perfect as a first lead-rein pony for Tabs. Yet very unexpectedly on his daily walk, he went from happily walking out the previous day to seriously lame in all four hooves alongside very worrying, very laboured breathing – all typical signs of acute laminitis. This literally happened overnight - the previous day he'd been fine; the next, he wasn't.

Although we instantly alleviated his symptoms, there had been other niggling signs on the sidelines - even though we were still getting to know him, we were approaching summer and it was obvious that his winter coat wasn't shifting. He was also noticeably drinking and weeing excessively and saturating his stable. We suspected Cushing's and got him tested. It came back positive.

Cut to 2014 ...

... and Tabby's now third pony, Cookie (pictured above), also started presenting with the classic non-shedding curly coat, still holding onto it in August. Cookie was a hairy 13.2hh Gypsy cob with a polar-bear coat in winter, so trust me when I say her non-shedding curly coat was duvet-thick. She was also noticeably lethargic, plus she seemed so sad which was very out of character for her. She was just 14-years old at the time.

Dinks and Cookie were our two Cushing's ponies who we kept comfortable till their passing. For the last couple of years of Cookie's  life she'd started having seizures, until one day she went down and didn't get up, so we had to make that final call. We knew it had been coming, but it's still never easy. She made it to the age of 22 and was one in a million, one of the sweetest girls you could ever meet, with a princess-pony mane you could bury your face in. She's back home now, in a shiny wooden casket under the TV, so we can still chat to her,

Cookie taught me more about PPID awareness, and the subtleties of ageing than any textbook ever could, but both Dinks and Cookie opened my eyes to how individual PPID truly is. No two horses look the same, and no two paths unfold the same way.

The hormonal chain reaction - what’s really driving those changes

Hormones are like text messages telling the body what to do, and when dopamine neurons decline:

• the messages get blurry
• the pituitary shouts louder
• the horse’s internal rhythm loses its tidy edges

This can affect:

• coat transitions
• energy
• appetite
• stress response
• immune rhythm
• water balance
• fat distribution
• mood

Not all symptoms = PPID - but PPID can include many of these symptoms.   Again - iIt’s a pattern, not a moment.

And so begins the metabolic effect

As if managing all-things-PPID isn't a juggling act enough, cortisol also increases blood sugar levels and enhances the brain’s use of glucose.

Reminder - when the horse is anxious, signals are sent to the adrenal glands to release adrenalin and cortisol, which triggers the fight/flight response. As long as this response in the body stays active, cortisol continues to release sugars into the bloodstream, which automatically triggers the release of higher levels of insulin - and here comes the side effects of high cortisol levels.

We're looking at abnormal glucose metabolism leading to weight gain, typically cresty necks, rear/belly fat pads, and ... insulin resistance (IR) - all the precursors to metabolic laminitis. It’s a vicious cycle - as cortisol levels increase, so insulin levels must then increase to try and keep glucose within what the body thinks are ‘normal’ levels. In humans, we call chronic, unregulated levels of insulin Type 2 Diabetes.

Getting the PPID/IR controlled and managed is essential in order to minimise the associated laminitis risk, so focusing on reducing stressors and keeping anxiety at bay will help control the cortisol levels.

Meanwhile, the circadium rhythm is busy determining sleeping/feeding patterns, brainwave activity, hormone production, cell regeneration and other biological activities. Come autumn and with the daylight hours becoming shorter and a drop in temperatures, it's normal for ACTH levels to increase when the body’s natural hormone levels tell the winter coat to start growing. So for a PPID-diagnosed horse we're now getting higher cortisol levels on top of already-high cortisol levels.

What is absolute cast-iron with PPID is that the endocrine system needs stabilising with hormone - and adrenal - support. Then when the IR kicks in, there's the absolute need to manage the IR/blood glucose levels, and the ever-present lami risk. Some of the symptoms of both PPID and IR will overlap despite the two being kind of mutually exclusive, but as Dr Eleanor Kellon (head of the ECIR group) says, “Every Cushing's horse will get IR.”

As if PPID wasn’t challenging enough with the stress and lami risk, PPID and IR can also lead to immune system overreactions like allergies, weight gain/weight loss, runny eyes, swollen sheaths/udders, excessive drinking/peeing, muscle loss, depressed immune system, and slow wound healing.

So what the heck do we do?

Prascend (Pergolide)

Convention these days says that PPID should be managed with one particular drug, Prascend - being the brand name of the active ingredient Pergolide, and the IR managed with diet as per the typical metabolic/EMS protocol (see our Metabolic Horse page).

However, the renowned ECIR group run by Dr Kellon (reminder, Dr Kellon is a vet) takes a slightly different stance, in that (quote): "Prascend should be the first line treatment for obviously advanced and/or laminitic horses with PPID. If it's an early case, feeding Agnus castus is a reasonable first step as long as the owner and veterinarian realise it may lose effectiveness." 

However ... Dr Christina Fritz, of Sanoanimal, has a different view (quote): "There is hardly a drug that is currently as controversial in equine therapy as Prascend. For some it is the magic bullet that should be given to every horse with metabolic problems, because they think it magically removes all worries such as laminitis and the like. On the other hand, there are just as many horse owners and therapists who demonize it because more than one horse has had to struggle with serious side effects or simply did not respond to the administration of this very expensive drug at all. It is therefore urgent to take a closer look at what we are actually dealing with here."

Dr Christina Fritz is a Biologist with a PhD in Animal Physiology/Neurobiology, and has been treating horses since 2006, focusing on metabolic therapy using holistic feeding methods via healthy, natural horse nutrition. She publishes in German, but with the help of Google Translate, here are some salient points from a valuable study she carried out on Prascend:

• Shortly after the market launch of Prascend, the manufacturer began not only with the targeted training of vets on equine Cushing Syndrome and everyday diagnostics about the ACTH value, but also with offering a free ACTH test for horse owners. This has massively fueled the number of Cushings' diagnoses, despite perfectly healthy horses being diagnosed via the ACTH test for Cushing's, and subsequently been prescribed Prascend.

• There is no basis for this diagnosis, as a healthy horse can also show increased ACTH levels, both circadian and over the course of the seasons, as well as when under stress. To infer the presence of a pituitary adenoma from an increased ACTH level is scientifically simply wrong.

• A pituitary adenoma leads to a permanently elevated ACTH level, but an elevated ACTH level does not always indicate the presence of a pituitary adenoma.

• The free Cushing Test has proven to be the best marketing measure, since sales have soared since then for a disease that until then had justifiably been a specific niche condition in veterinary medicine.

End quote. Sadly the page link to her study doesn't seem to work, but here's the link all the same in case it comes back: - https://wissen.sanoanimal.de/2021/02/03/wie-wirkt-prascent/?fbclid=IwAR2dGnRpDRhUelCrkDPhyoX8xcnNXNXCEWkSg_G8iksDRiJw3GP6fwXj_pM

So why Prascend?

Put simply, it mimics dopamine, stepping in for the neurons that are no longer producing enough of it.

And here's the line Dr Kellon puts perfectly – the one that finally helps owners understand what's actually happening:

“You cannot stimulate a dead cell.”

Once dopamine neurons are gone, they’re gone. Which explains:

• why early PPID behaves differently from later PPID
• why dosage often needs adjusting over time
• why some horses do perfectly on Prascend and why others struggle
• why some horses seem absolutely fine despite big ACTH numbers
• why dopamine-supportive herbs only make sense in horses not on Prascend

It's not failure - it's simply how this condition unfolds.

Natural plant therapy

There is another way. With it being known that plant extracts have less side effects, natural therapy may well be safer for long term use.

First up, there's no doubt that the berries from the revered Vitex agnus-castus tree are renowned for helping Cushings/PPID horses, with many peer-reviewed studies showing as such. Used for its gentle, tonic action on the anterior pituitary's action in adrenal hormone regulation, agnus-castus is an amphoteric herb, meaning it may help maintain normal hormonal levels, rather than cause them to go up or down.

NB - while it can certainly help with the visible presentations, it won't necessarily control the ACTH levels. (Not wishing to fly in the face of science, but personally we had remarkable success with both Dinks and Cookie, alongside the amino acid Tyrosine as the dopamine stimulant).

However, Dr Kellon posts against feeding agnus castus berry alongside Prascend: https://drkhorsesense.wordpress.com/2021/05/18/mixing-chastetree-berries-with-pergolide-in-cushings-horses/.

Then there's Mucuna pruriens, with the rather catchy common name of Kapikacchu, which has natural sources of L-DOPA to enhance circulating dopamine levels similar to medications, but offers added benefits of supporting nerve, brain, and pituitary axis functioning to target nerve function through antioxidant and anti-inflammatory support.

However, again, as with agnus castus, it's not recommended to feed Mucuna if your horse is on Prascend, as it could result in an over-production of dopamine, possibly resulting in over-stimulated side effects. Hence why we have two CushTonic blends to support the PPID horse - CushTonic-1 for horses not on Prascend, and CushTonic-2 for horses on Prascend, which excludes the agnus-castus and mucuna.

Other useful herbs

• Another renowned plant, Milk Thistle (Silybum marianum), or more precisely its seeds, are renowned to support the liver's biotransformation function of drugs and toxins for excretion. Another function of the liver is to denature circulating hormones, thereby helping to keep the balance of hormones in the body.

• Ashwagandha (Withania somniferum), probably my favourite adaptogen herb featuring in both our Cushing's and Stress formulas. Adaptogens literally do what it says on the tin - they help the body 'adapt', and Ashwagandha is no exception, being a renowned herb for helping the adrenal glands 'normalise' their response to stress levels, resulting in rebalancing cortisol levels.

• Astragalus (Astragalus membranaceous) is another popular stress-normalising adaptogen. In particular, Astragalus is high in polysaccharides, constituents that assist the body's normal immune response, hence why its known as an immunostimulant.

• Sarsaparilla root (Smilax officinalis) has a long-standing reputation for helping the body excrete toxins via the lymphatic system, as well as being a beneficial liver supporter. We use it in many of our blends.

• I also love Brahmi (Bacopa monnieri), taking it myelf in tincture form to support cognition. Brahmi is both an adaptogen and an antioxidant, helping to counter stress and contribute to healthy mood and cognitive function.

• And when the IR sets in, feed our MetaTonic at opposite ends of the day to our CushTonic range.

What I can also absolutely guarantee you is that the right nutrition also goes a huge way to help. PPID is a degenerative condition that requires whole-body nutrition for health and wellness - see our Feeding our Horses/Why what we feed has to be right page.

Sadly we know there's no cure for PPID, but the good news is that once it's been diagnosed, management is reasonably straightforward and can help a horse return to a comfortable lifestyle.

Top Tips

• Lower cortisol and increase dopamine levels naturally. Keep levels balanced by maintaining a happy equilibrium; exercising and allowing quality rest, alongside feeding a natural, species-appropriate diet and balancing forage chemistry with an appropriate mineral supplement.

• Movement is key! It’s the best IR-buster there is, but it goes without saying that we never force a sore equine to move. Exercise not only rids the body of fat cells, but it also increases dopamine levels - remind yourself how you feel after a great ride. Regular exercise also helps to burn the extra blood sugar made available from elevated cortisol levels.

• In addition to the countless physical benefits, exercise can also have psychological benefits. Studies show that exercise can increase the amounts of both dopamine and serotonin neurotransmitters in the brain, as well as helping your horse feel more energised overall. In a May 2007 article in the Journal of Neuroscience, it was noted that exercise could cause the brain cells that use dopamine to work more efficiently, and an August 2007 article in the journal Neuroscience Letters, noted that continuous exercise also reduced damage to brain cells that release dopamine.

• Quality rest time helps lower cortisol levels because otherwise the body’s nervous system stays in a state of alertness that requires cortisol. Getting proper rest also increases serotonin and dopamine, which help control feed cravings.

Useful supplements

• Feed omega-3 fats via micronised linseed (not linseed oil) as they help trigger the production of serotonin, as well as being a good food source of the trace mineral selenium. A low intake of this nutrient has been linked with depression.

• The body needs the B-vitamins to help lower cortisol levels, with the equine gut microbiome producing them in the active form that the body recognises and knows what to do with - not a synthetic supplement. So, maintaining a healthy microbiome and feeding plenty of long, stemmy, fibrous hay in the diet for the hindgut microbes is extremely important. If your horse has a disrupted gut function at any time, feed B6 in its activated form, P5P, for at least a month until gut function is restored back to a healthy normal.

• Turmeric's active ingredient, curcumin, shines when it comes to brain health. A double-blind, placebo-controlled study included 40 adults between the ages of 50 and 90 with reported mild memory lapses but no dementia. Those who received curcumin supplementation saw significant improvements in memory and concentration, while the control group experienced no improvement. https://www.sciencedirect.com/science/article/pii/S1064748117305110?via%3Dihub

• Acetyl-L-carnitine is a much researched amino acid which has numerous beneficial effects on brain metabolism, also serving as a potent antioxidant, protecting against neurotoxic insults, and has been shown to benefit certain forms of depression. It's also well researched in human medicine and proven beneficial in Parkinson’s patients. It's known to benefit fat metabolism which makes it beneficial for leptin-resistance, another detrimentally-affected hormone instruction as a result of IR - https://www.ncbi.nlm.nih.gov/pubmed/22549035 (also covered in full in our EMS/IR Metabolic page).

• Finally, to those orbital pads above the eyes - some people think what looks like swollen pads above the eyes are fat; others think it’s Cushing’s. The good news is that they’re not fat – there’s no tissue here for fat cells to grow in; nor are they Cushing’s related. Anatomically there’s a lot of connective tissue and facia here, so it’s more likely lymph, not fat. Long and short, they’re just one of many indicators that the metabolism is out of order. When you get the metabolism back on track (via a good gut restoration and detox programme and relooking at feed), these pads tend to go away.

Steps to lower cortisol and stimulate dopamine levels naturally

• Follow a daily regime of 20-30 minutes exercise, even if it’s just a brisk walk on the lead rope. The body's reaction to exercise creates brain activity that regulates hormone and brain chemicals.

• Add a forage-balanced mineral supplement that supports good overall health and balances your forage/grazing. Avoid sugar, grains, bad fats (PUFAs), and processed feeds which can also cause dopamine levels to drop.

• Feed extra Tyrosine - dopamine is produced by the body from the amino acid tyrosine, which in horses is one of the non-essential amino acids, i.e. those that the organism can produce itself and does not have to get in via food.

• In addition to supporting overall health, Vitamin C is helpful in supporting dopamine. A horse's liver synthesises its own vitamin C from glucose in the liver, producing about 72-grams each day; however, a PPID horse may have compromised liver function so adding rosehips to the feedbowl can help as they're jammed full of vit.C.

• A calm, happy horse with horse buddies creates positive brain activity, increasing the amount of feel-good substances such as dopamine and seratonin.

Bottom line…

Supporting a hormone-stressed horse is not about chasing numbers, labels, or perfection.  It’s about restoring steadiness – environmentally, emotionally, nutritionally, and rhythmically.

With calm foundations in place, many horses regain their natural sparkle, steadier coat changes, and a sense of comfort in their own skin.  

Update - Jan'2019

When our Cookie had a worrying seizure episode (which I suspected was related to her Cushings) I found the following related notes courtesy of The Chronicle of the Horse forum (which sadly no longer seems to be around as the link no longer works).

I should add that the forum post dates back to 2006 so in theory it’s outdated; however, in 2019 I still found the following info useful. Credit due to poster Melyni (PhD) PAS, Dipl. ACAN, answering a question from poster ‘equineelders’, of Travellers Rest Equine Elders Sanctuary, whose horse had presented with seizures similar to Cookie:

“At AAEP in early Dec I attended a couple of talks on Cushings. The current thinking was that it isn't tumour per se of the anterior pituatary but a loss of the dopaminergic neurons that descend from the hypothalmus into the pars intermediar.

If I understand it correctly these neurons have an inhibitory effect on the cells of the pars intermedia, and thus the loss of the neurons means a loss of the inhibition, thus the pars intermediar cells begin to put out more and more hormones, esp ACTH plus others, which leads to a secondary hypocorticoidism.

It's thus more similar to Parkinson's than to a tumour. Patients with Parkinsons suffer from neurolgical symptoms, such as muscle rigidity, spasms and loss of balance. Loss of control of fine motor neurons occurs as well.

So if you think about Parkinsons as the underlying cause (loss of dopaminergic neurons) rather than a cancerous growth, the symptoms make more sense. Not that this helps anyone dealing with a seizuring horse.

There is a theoretical way to modify the intake on amino-acids to enhance the dopaminergic pathways, as opposed to the seratonergic, eg don't feed tryptophan; supplements that contain the amino-acids threonine and tyrosine are effective, but this is not scientific only anecdotal.

Seratonin is made from different precursors than dopamine. They are both made from amino-acid precursors but not the same ones, and there is some indication that increasing the seratonin in Parkinsons’ patients exacerbates the symptoms, as the pathway may be competitive.

Dopamine comes from Tyrosine and Threonine, while Seratonin comes from Tryptophan via the 5HT pathway. Arginine may also be involved in the dopamine pathway.

How do chromium and magnesium fit into this? We have a few on supplements per vet's recommendation, but I don't know specifically what they are doing. From what I have read in such literature as exists, the Mg helps with the peripheral circulation, as in it keeps the small arterioles open and maintains the circulation to the extremities (all data from human studies) thus it (may) minimise the loss of blood flow to the feet, and the subsequent laminitis. It also seems (in humans) to have an anti-inflammatory effect, as in, it reduces C reactive proteins from the adipose tissue.

Chromium is part of the enzyme system that picks up the glucose from the blood stream and enters it into the cell. Thus the extra chromium helps to clear the bloodstream of the glucose, and the extra magnesium helps to maintain peripheral circulation.

All this information came from human studies, and thus you cannot be too literal in saying that this is what happens in horses, as these things don't always transfer from species to species, but as there is next to no research in horses, that is all we have. I do know from what work I have done, that giving the Cr and Mg to pre-Cushings and Cushings horses you get better laminar bloodflow and a reduction in the symptoms, such that the pergolide dosage can be reduced.

We have measured the reduction in neck thickness and in the abnormal fat pockets, and we can show an improved circulation to the foot. But these effects aren't treating the underlying cause.

Giving essential amino acids to these horses reduces the loss of muscle tissue and the muscle wasting. Again this is treating the symptoms, not the cause, but overall the horses look and feel better, and are more active, which in itself improves their metabolism.”

As a result of this information, I started adding Tyrosine into Cookie's feedbowl.

Update - June'21

A recent 'Dr K's Horse Sense' post shows that onset pain may also affect ACTH testing, as it's known that both ACTH and cortisol levels are more likely to be higher than normal ranges in acute illness.

A 2020 German study looked at hospitalised horses in pain from various sources including colic, laminitis and orthopedic presentations, and with no clinical signs of PPID. The study found that "... acute pain resulted in markedly elevated cortisol and insulin resistance."

Since acute stress, wounds etc., can cause the adrenal glands to release cortisol without ACTH increase, it’s unclear from that study if acute pain will influence ACTH, although it certainly increases insulin. The thinking is that testing for both ACTH and insulin levels should be avoided in the first 24-hrs after onset of pain.

See the full article here: https://drkhorsesense.wordpress.com/2021/06/08/insulin-acth-and-pain/

Update - Feb'2026

Dr Kellon also mentions that more recent research (Horner et al., McFarlane et al. 2024–26) has shown that some horses with hormonal change are less resilient to internal parasites than their younger or non-PPID counterparts – likely because hormonal shifts influence immune rhythm.

Useful approaches:

• check FECs at 45 and 90 days after deworming
• adjust frequency based on your actual horse
• keep samples fresh and chilled

Not every horse is affected this way – but it’s a helpful insight to keep in mind when building an overall care plan.

That's it for now! Meanwhile, click on the SHOP link below to see our supporting Cushing's/PPID product range.