What is PPID or Cushing’s in horses?


Pituitary Pars Intermedia Dysfunction (PPID) was formerly called Cushing’s disease in horses. It’s a disorder that results from a tumor.


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  • Inside your horse’s brain, the pituitary gland decides to start growing a tumor. This growth then makes the pituitary gland do its job – but more. The pituitary gland is a lot like the motor of the endocrine system of your horse, and the tumor makes it pump out more adrenocorticotropin (ACTH). This ACTH, in turn, increases the output of cortisol, which cascades into the trademarks of Cushing’s disease.


  • Cortisol is the “stress hormone” which can lead to increased insulin levels and perhaps insulin resistance (IR), a higher risk of laminitis, and the typical obvious signs of PPID, such as the wooly haircoat and muscle loss. While cortisol is necessary for life, it’s just plain rude to increase our body’s stress. What a jerk.


  • PPID is usually a condition found in older horses, about 15 or older. Of course, there are exceptions to the rule. Ponies and some horse breeds, like the Morgans, are more likely to develop PPID. Dang those naughty ponies!


fuzzy horse with cushings in summer wearing a bridle

This particularly lovely horse must be clipped all year because of PPID.


Typical signs of PPID in horses


  • You can’t just look at a horse to make an official diagnosis, but if you know what to look for, you can see some health trends early in your horse. This is true especially if you combine your observations with your Vet’s input and actual, legit tests for PPID.


  • PU/PD – This means polyuria and polydipsia, which is excessive drinking and excessive urination.


  • Your horse might be lethargic. If he likes to live behind your leg, he may seem more lethargic.


  • He may sweat excessively.


  • Your horse may start losing topline muscle or wasting muscle in other major muscle groups.


  • He may start to look differently in his face. You might see fat deposits over his eyes, or he might have a head tilt.


  • Broodmares and stallions might start to lose fertility.


  • Laminitis and other hoof problems, such as abscesses, happen easily in horses with PPID.


  • Your horse might also have sinus and/or tooth infections. A quick sniff of your horse’s mouth and paying attention to how he eats can alert you here.


  • Your horse with PPID might also have insulin resistance (IR). This is when your horse’s body has trouble recognizing insulin, so it makes more and more of it. Details here, in an article about EMS.


  • The most commonly known sign of PPID is hirsutism, the thick hair coat that doesn’t shed easily. Many horses with PPID do not exhibit this. But, it’s a fairly clear indication that a horse with hirsutism will have PPID.


Just because your horse is not a hairy yak doesn’t clear him of PPID, he could still have it.


vet taking blood from the jugular vein of a horse

Blood tests for PPID are easy and quick.

How to test your horse for PPID.


  • There are two primary ways to test for PPID. One is the dexamethasone (dex) suppression test, and the other is the ACTH concentration measurement.


In the dex suppression test, your horse’s cortisol level is measured in the afternoon.


  • Then, a dose of dexamethasone is given. Dex will reduce cortisol levels in normal horses. Almost a day later, cortisol levels are measured again.


  • If the horse has PPID, the dexamethasone will not dent the cortisol level.


  • Cortisones, like dex, can be related to developing laminitis. There is conflicting evidence about administering this test to a horse with a history of laminitis. Some say it’s fine; others say this test is too risky. Some say that it should be avoided in a horse with active laminitis and all other times are just fine. Your Vet can help you out with this.


  • There is also the chance of confusing results in the fall. If the test is given in the fall, a positive test could be false. However, a negative test in the fall is conclusive. This is because your horse will naturally increase his ACTH levels in the fall to prepare for winter. Incidentally, this increases his chances of laminitis in the fall.



trail ride in the fall on chestnut horse

Fall and winter mean a natural increase for ACTH in horses.


The other test for PPID involves measuring your horse’s ACTH.


  • This simple blood draw should also be interpreted according to the time of year it was administered. In the fall, your horse’s ACTH levels increase to help your horse prepare for winter. If tests results are also high in the spring and summer, it’s likely PPID. But a horse with high ACTH in fall but normal in the rest of the year may be just fine.


  • Your Vet may also want to test for insulin resistance, which can be part of your horse’s PPID, or it could be just Equine Metabolic Syndrome (EMS). IR is part of the bigger metabolic picture.


How to manage Cushing’s in horses


  • PPID cannot be reversed or cured, but it can be managed. Pergolide and cyproheptadine are two drugs that may help your horse. Pergolide is the active ingredient in Prascend®. Your Vet will need to follow up with some bloodwork to be sure your horse is receiving the proper dosage.


  • An interesting fact about pergolide, it was originally designed for human Parkinson’s patients, and its use in horses is considered off-label. You may remember a scare a few years ago when the FDA recalled pergolide because of human health concerns, but horse owners rallied and the FDA decided to allow the compounding of pergolide for horses. You still need a prescription, too.


hay in water trough

Soaking hay is helpful!


Management starts with diet


  • You will also need to manage your horse’s diet, especially if IR is part of your horse’s metabolic picture.


  • Low sugar and low starch diets are key here. Use fats for added calories. You may want to switch hays to a lower starch variety, and removing all feeds that are not low starch is a good idea. If you feed a fortified feed, you will need to replace the balanced vitamins and minerals of that feed with a supplement. This is where an Equine Nutritionist comes in – so many things in horse feed can help and hinder a horse. You want to get the diet right.


  • A good example of finding the best supplements for PPID involves selenium, a handy and helpful anti-oxidant. Selenium is found in forages and pasture and can be detrimental if your horse’s diet is deficient, and toxic at high levels. It’s this balancing act that is best left to the Equine Nutritionist.


  • Many supplements on the market help with Cushing’s in horses.  Quiessence, EquiShure, and the like target different aspects of the disease. 


  • You can also soak your horse’s hay to reduce those sugar levels. This is easy to do, and if you can use hot water, it’s rather quick.


  • It’s ideal for the horse with PPID to avoid pastures or have minimal access to pasture. Using grazing muzzles in addition to shorter times on grass is helpful. Dry lots are key here!


close up of grazing muzzle on a paint horse

This is a super snazzy Greenguard Equine Grazing Muzzle.


PPID is also fantastic at taking your horse’s immune system and flushing it down the toilet.


  • Your horse will have a more challenging time fighting infections and worms and abscesses. Keep up with vaccines, a fecal egg count and targeted deworming situation, dental health, and hoof care.


  • This also means that the usual cuts and scrapes can be much harder to heal and have an increased susceptibility to infections. Try and avoid using dirt as a band-aid in these situations.


  • Do regular bloodwork to monitor ACTH levels and watch out for increased insulin and glucose which may indicate Insulin Resistance. This is quick, inexpensive, and gives you and your Vet a snapshot of how your efforts are working.


  • If your horse is sound – keep exercising! This is good for everyone, and it’s part of the reasons we have horses.


Have you managed a horse with Pituitary Pars Intermedia Dysfunction?




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