An older horse that doesn't shed its winter coat, drinks more than it used to, and loses muscle over the back: that combination often points to Cushing's disease, officially called PPID. It's one of the most common hormonal disorders in older horses and ponies, and at the same time one that responds well to treatment. This guide explains what happens in the body, which signs deserve serious attention, how the diagnosis works, and what daily management looks like.
What PPID Is
PPID stands for pituitary pars intermedia dysfunction: a condition in which part of the pituitary gland (a small gland at the base of the brain) becomes dysregulated. That gland normally controls the hormone balance. With PPID, the inhibition on part of the gland is lost, so it starts producing too many hormones. That excess affects the whole body: coat shedding, muscle development, fat distribution, immunity, and metabolism.
The condition mainly occurs in older animals, usually from around age fifteen, and just as much in ponies as in horses. PPID develops slowly. Precisely because of that, the first signs are often dismissed as "just old age", while early intervention makes a real difference.
The Signs at a Glance
The best-known picture is the coat: long, often slightly curly, and a winter coat that doesn't shed in spring, or only sheds halfway. A coat that no longer sheds at all belongs to an advanced stage, according to the Equine Endocrinology Group (an international group of veterinarians focused on hormonal diseases in horses). Earlier on, the signs are often subtler, such as a coat that sheds later in some areas, less muscle over the back, lethargy, or reduced performance. These are the signs that can go with PPID:
| Sign | What You See |
|---|---|
| Coat problems | Long, sometimes curly coat; slow or incomplete shedding; sweating in warm weather |
| Drinking and urinating more | The water bucket empties faster, the stall is wetter than before |
| Muscle loss | The back and croup muscles shrink; the topline sinks in, sometimes with a pot belly |
| Fat deposits | Fat pads in fixed spots, for example above the eyes or on the neck |
| Lethargy | Less energy and willingness to work; the horse looks "aged" |
| Recurring infections | Skin problems, abscesses, or wounds that heal slowly; stubborn worm infections |
| Laminitis | Sensitive movement, a creeping or acute episode, sometimes the very first sign |
That last one deserves particular emphasis: almost a quarter of horses with PPID develop laminitis, according to the Utrecht University Veterinary Hospital (UDI). That mostly happens when insulin regulation is disrupted as well, and some horses are only tested after an episode. For any older horse with unexplained laminitis, the question of PPID and of disrupted insulin regulation belongs on the table.
Why Early Recognition Pays Off
PPID can't be cured, but it can be managed well, and the earlier you start, the sooner you can limit complaints and complications. Recognized early, you start treatment before the complaints have progressed far, and you reduce the chance that the first sign is a laminitis episode. If you wait until the classic picture is complete, muscle mass has often already been lost, and the horse has been walking around with simmering complaints for months or years.
If you're unsure about coat shedding, drinking behavior, or condition in a horse over fifteen, discuss it with your veterinarian. An annual check-up is a good idea for older horses regardless; you can read about that bigger picture in caring for a senior horse.
Diagnosis: Blood Testing by the Veterinarian
The veterinarian makes the diagnosis using blood testing, combined with the clinical picture and history. Usually the vet measures the amount of ACTH in the blood, a hormone from the pituitary gland, sometimes also after stimulation with the hormone TRH. The time of year affects how the result is interpreted: the cut-off values are higher in autumn, and in ponies such as Welsh and Shetland ponies, ACTH can be high in autumn even without PPID. The veterinarian therefore decides when and how testing happens, and testing a horse without signs isn't recommended. If a horse has acute laminitis, the vet waits to test until the pain is under control. In a borderline case, a retest follows after three to six months. Because PPID often goes together with disrupted insulin regulation, the vet also looks at insulin. After treatment starts, blood testing follows to see whether it's working: a first time after one to three months, then every six to twelve months.
Daily Management
Once the diagnosis is confirmed, management consists of a fixed set of elements. Lifelong, but easy to fit into a normal stable routine.
- Medication from the veterinarian. Medication (pergolide) exists that suppresses hormone production; the veterinarian prescribes it and adjusts the dose based on blood checks. Because the disease progresses slowly, the dose often needs adjusting over the years. You often see improvement within a few weeks: more energy and a coat that starts shedding again. Giving the medication daily and consistently is the core of the treatment.
- Feeding by condition and insulin. What a PPID horse can eat depends on its condition and on whether its insulin regulation is also disrupted. That is the case in about a third of horses with PPID. Then the same rules apply as for EMS: low-sugar forage and limited turnout. If your vet has confirmed with a sugar test that insulin regulation is normal, you don't need to restrict sugar and starch. Many PPID horses are lean and lose muscle instead; they benefit from extra fat, protein, and calories, for example through good-quality senior feed, fat supplements, or alfalfa. Have the ration drawn up with your veterinarian or a feed advisor and check your horse's condition often, because feed requirements change with age. Weight loss shouldn't become a side effect of the diet.
- Clipping for coat problems. A horse that keeps its winter coat gets uncomfortably hot in summer and sweats heavily. Clipping, potentially several times a year, is a practical solution. More on coat changes and rug policy is in seasonal coat care.
- Extra attention to teeth, hooves, and parasites. Because of the lower immunity, problems take hold more quickly. Keep dental checks tight, have the farrier tend to the hooves every eight to ten weeks, check wounds and skin extra carefully, and discuss the deworming approach with the veterinarian: fecal egg counts are especially worthwhile for these horses.
- Laminitis prevention. Watch daily for sensitive movement, warm hooves, or a bounding digital pulse, be cautious with turnout on young, fast-growing grass, and call the veterinarian immediately if in doubt. Acting quickly at the start of an episode is the difference between a short episode and lasting damage.
Living with a Cushing's Horse
A PPID diagnosis isn't the end of a horse's working or happy life. With daily medication, suitable feed, and an attentive owner, many horses still have years of quality of life ahead, often including light to normal work, if condition and hooves allow it. According to the Equine Endocrinology Group, the vast majority of owners report a good quality of life, and PPID doesn't necessarily mean a shorter life, though an older horse remains prone to other age-related conditions. The condition mainly demands consistency: the medication every day, the feed reviewed every season, the blood check once or twice a year. Once you've got that rhythm down, you'll find that a Cushing's horse remains surprisingly, simply, a horse.
In Short
- PPID (Cushing's disease) is a hormonal disorder caused by a dysregulated pituitary gland, mainly in horses and ponies from around age fifteen.
- Classic signs: a long coat that sheds poorly, drinking and urinating more, muscle loss over the back, fat deposits, lethargy, and slow-healing infections.
- The biggest risk is laminitis, sometimes the first sign; test any older horse with unexplained laminitis.
- The veterinarian makes the diagnosis with a blood test for ACTH; after that, testing follows once or twice a year to see whether treatment is working.
- Management is lifelong: daily medication from the veterinarian, feeding by condition and insulin, clipping for coat problems, and tight upkeep of teeth, hooves, and deworming.
- Recognized early and managed well, many Cushing's horses still have years of quality of life ahead.
Sources (verified September 2, 2026, signs, diagnosis, and management November 2, 2026): Utrecht University Veterinary Hospital: PPID (Cushing's disease) · Equine Endocrinology Group: Recommendations for the Diagnosis and Management of Pituitary Pars Intermedia Dysfunction (PPID), 2025 · KNMvD (Royal Dutch Veterinary Association): Leidraad Hoefbevangenheid Paard (Guideline on Laminitis in Horses), version March 16, 2026 · Merck Veterinary Manual: Hypertrichosis Associated With Adenomas of the Pars Intermedia in Horses
See also: Caring for a senior horse · Laminitis in horses · Seasonal coat care · Glossary: Cushing's disease (PPID) · Level: Considering Your Own Horse