How To Monitor Cushing’s Disease in Horses
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How To Monitor Cushing’s Disease in Horses
By Dr Duncan Houston
Monitoring PPID is not just checking ACTH once a year. It is tracking treatment response, insulin risk, laminitis danger, appetite, weight, muscle, hoof health, infection risk, and overall quality of life.
Equine Cushing’s disease is more accurately called pituitary pars intermedia dysfunction, or PPID. It is a slowly progressive endocrine disease of older horses, ponies, and donkeys. Current Equine Endocrinology Group guidance describes PPID as an age related degenerative disease involving dopaminergic neurons in the hypothalamus, leading to abnormal hormone production from the pars intermedia of the pituitary gland. (Squarespace)
The key owner mistake is thinking PPID is only about a long curly coat. The coat matters, but the bigger risks are laminitis, insulin dysregulation, muscle loss, recurrent infections, poor wound healing, dental and hoof problems, and loss of quality of life. PPID becomes more common with age, with current guidance reporting prevalence around 20 percent in equids over 15 years and 30 percent in equids over 30 years. (Squarespace)
Quick Answer
Cushing’s disease in horses, or PPID, should be monitored through clinical signs, ACTH testing, insulin testing, laminitis risk, body condition, appetite, coat changes, hoof care, dental health, and response to pergolide treatment. Current guidance recommends interpreting ACTH results alongside season, breed, clinical signs, and the horse’s overall health, not as a single isolated number. PPID is often accompanied by insulin dysregulation, so insulin testing is essential because laminitis risk is one of the most important threats to manage. (Squarespace)
What Is PPID in Horses?
PPID is a progressive endocrine disorder affecting the pituitary gland. It is commonly called Cushing’s disease, but that name can be misleading because equine PPID is not simply the same as Cushing’s disease in dogs or people.
In PPID, degeneration of dopamine producing control pathways allows the pars intermedia of the pituitary gland to become overactive. This can lead to increased ACTH and other related hormones and peptides. The result is a broad syndrome that affects the coat, metabolism, immune function, muscle, hooves, drinking, urination, sweating, behaviour, and general health. (Squarespace)
Common signs include:
| Sign | Why it matters |
|---|---|
| Long curly coat or delayed shedding | Classic sign of PPID |
| Muscle loss over the topline | Common in older PPID horses |
| Pot belly appearance | Often linked with muscle loss and age related change |
| Increased drinking and urination | Can occur with PPID or other disease |
| Abnormal sweating | May be increased or altered |
| Lethargy or reduced performance | May reflect PPID, pain, age, or another condition |
| Recurrent infections | PPID can reduce immune resilience |
| Slow wound healing | Important monitoring clue |
| Laminitis | One of the most serious complications |
| Regional fat deposits | May indicate concurrent insulin dysregulation |
| Hoof abscesses or hoof problems | May reflect immune, hoof, or laminitis related issues |
MSD Veterinary Manual lists hypertrichosis, delayed shedding, lethargy, decreased performance, regional adiposity, recurrent infections, muscle loss, increased drinking, and increased urination among recognised PPID signs. (MSD Veterinary Manual)
Why Monitoring PPID Matters
PPID does not stand still.
A horse may start with mild delayed shedding and later develop muscle loss, laminitis risk, infections, dental disease, changing feed needs, or medication adjustments. Monitoring is how you catch those changes before they become crises.
The three biggest monitoring goals are:
| Monitoring goal | Why it matters |
|---|---|
| Control PPID signs | Shows whether treatment is helping |
| Detect insulin dysregulation | Reduces laminitis risk |
| Protect quality of life | Keeps the horse comfortable, functional, and safe |
The Equine Endocrinology Group states that improvement in clinical signs is the most important indicator of treatment response, and that monitoring in the same season from year to year is important because ACTH changes seasonally. (Squarespace)
How Worried Should You Be?
| Risk level | What it looks like | What it means | What to do |
|---|---|---|---|
| Low concern | Horse is diagnosed, bright, eating well, coat and muscle stable, no laminitis signs, insulin controlled | PPID appears stable | Continue medication, routine monitoring, hoof care, dental care, and scheduled testing |
| Moderate concern | Coat still abnormal, mild weight or muscle change, drinking more, appetite change, mild lethargy | PPID may need reassessment or another issue may be present | Book a vet review and discuss ACTH, insulin, diet, teeth, pain, and parasites |
| High concern | Recurrent infections, poor wound healing, worsening muscle loss, hoof rings, foot soreness, uncontrolled insulin | Higher complication risk | Arrange prompt veterinary assessment and farrier involvement |
| Critical | Heat in feet, strong digital pulses, reluctance to move, shifting weight, severe infection, not eating, colic signs, collapse | Possible laminitis, systemic illness, medication complication, or emergency | Call your vet urgently |
The practical checkpoint is simple: PPID is chronic, but laminitis, severe infection, sudden inappetence, colic signs, or severe foot pain are urgent.
What Should Owners Monitor at Home?
The best PPID monitoring system is boring and consistent. That is a compliment. Boring systems catch problems early.
Track these signs every week or month:
| What to monitor | What to look for |
|---|---|
| Coat shedding | Delayed shedding, curly coat, patchy shedding |
| Body condition | Weight gain, weight loss, fat pads, topline loss |
| Neck crest | Increased crest can suggest insulin risk |
| Muscle | Topline loss, weakness, difficulty rising |
| Appetite | Reduced appetite, especially after pergolide changes |
| Drinking and urination | Increased thirst, wet bedding, more urine |
| Hooves | Heat, digital pulses, hoof rings, tenderness |
| Movement | Short steps, reluctance to turn, footiness |
| Infections | Skin infections, hoof abscesses, dental infections |
| Wound healing | Cuts that heal slowly or become infected |
| Behaviour | Lethargy, dullness, irritability, reduced performance |
| Medication | Missed pergolide doses, appetite changes, dose changes |
Current guidance also highlights body condition, hoof care, dentistry, parasite control, appetite, attitude, and demeanour as important parts of PPID quality of life monitoring. (Squarespace)
How Is PPID Diagnosed and Monitored?
The main tests used for PPID are ACTH testing and TRH stimulation testing.
Cornell lists commonly used PPID diagnosis and monitoring tests as combined baseline endogenous ACTH and insulin testing, TRH response testing measuring ACTH, and dexamethasone suppression testing. Post treatment follow up can include monitoring clinical signs and testing ACTH and insulin. (Cornell Vet College)
Baseline ACTH
A baseline ACTH test measures ACTH concentration from a blood sample. It is useful, but it is not perfect.
ACTH can be affected by season, breed, stress, excitement, illness, exercise, diet, sample handling, and laboratory method. UC Davis notes that baseline ACTH testing is good at detecting moderate to advanced PPID but may miss early disease. (Center for Equine Health)
TRH stimulation test
A TRH stimulation test involves collecting a baseline ACTH sample, giving TRH intravenously, then measuring ACTH again after a set time. UC Davis notes that this test may be useful for early PPID or inconclusive baseline ACTH results, although variability exists. (Center for Equine Health)
Insulin testing
Insulin testing is not optional fluff. It is one of the most important parts of PPID monitoring because insulin dysregulation is the major link between endocrine disease and laminitis risk.
The Equine Endocrinology Group states that PPID is often accompanied by insulin dysregulation and that insulin dynamics should be assessed alongside PPID testing. (Squarespace)
Why Season Matters for ACTH Testing
ACTH naturally changes through the year. That means a result cannot be interpreted properly without considering season.
Current Equine Endocrinology Group guidance emphasises that season and breed affect ACTH concentrations, and that clinical context and season are crucial when deciding whether to treat, monitor, or retest. (Squarespace)
This is especially important in Australia and other southern hemisphere locations. Many published seasonal ACTH tables are written for the northern hemisphere. The Equine Endocrinology Group notes that specific months in its ACTH tables are accurate for the northern hemisphere and require seasonal correction for southern hemisphere interpretation. (Squarespace)
In practice, try to compare results from the same season each year where possible. That makes trends more meaningful.
How Often Should PPID Be Rechecked?
A practical monitoring plan usually includes:
| Timing | What to check |
|---|---|
| At diagnosis | ACTH, insulin status, body condition, hoof status, diet, dental care, parasite control, laminitis history |
| After starting pergolide | Recheck clinical signs and often endocrine testing within 1 to 3 months |
| Stable treated horse | Reassess every 6 to 12 months, depending on risk |
| High risk horse | More frequent checks if laminitis, high insulin, poor response, weight loss, infections, or appetite problems occur |
| Seasonal review | Test in the same season year to year where possible, with special attention during seasonal ACTH rise |
The Equine Endocrinology Group recommends evaluating clinical signs with or without endocrine testing 1 to 3 months after starting pergolide, then every 6 to 12 months. UC Davis also recommends ongoing monitoring with retesting at least twice yearly, including one assessment in the fall, to determine whether medication changes are needed. (Squarespace)
Pergolide Treatment: What Should You Monitor?
Pergolide mesylate is the main medication used to treat PPID. The Equine Endocrinology Group lists daily oral pergolide mesylate as the mainstay of PPID treatment, combined with dietary management and general wellness care. UC Davis also states that there is no cure for PPID and that treatment is intended to reduce clinical signs for life. (Squarespace)
The current Equine Endocrinology Group guidance lists an initial pergolide dose of 2 micrograms per kilogram once daily, which is equivalent to 1 mg for a 500 kg horse, but this must be prescribed and adjusted by a veterinarian. (Squarespace)
Monitor for:
| Treatment response | What it may mean |
|---|---|
| Coat improves over months | PPID control may be improving |
| More normal shedding | Good clinical response |
| Better energy and attitude | Treatment may be helping |
| Appetite drops after starting | Possible pergolide associated inappetence |
| ACTH improves but signs do not | Another problem may also be present |
| Signs improve but ACTH remains abnormal | Dose change is not always automatic |
| Laminitis risk remains high | Insulin dysregulation still needs management |
| Recurrent signs return | Dose, compliance, testing season, or another disease may need review |
A very important nuance: ACTH may not always return to the PPID unlikely range even when the horse improves clinically, and abnormal ACTH alone does not always mean the dose must increase. (Squarespace)
What If Pergolide Causes Poor Appetite?
Some horses show reduced appetite when pergolide is started or when the dose is increased. This is sometimes called the pergolide veil by horse owners.
Current Equine Endocrinology Group guidance notes that this appetite reduction is often temporary. Strategies for persistent inappetence may include pausing administration for 3 to 7 days, restarting at a lower dose, gradually increasing over 1 to 2 weeks, dividing the dose, changing administration time, or consulting an equine internal medicine specialist. These changes should be made through your vet, not guessed at from the feed room wall of wisdom. (Squarespace)
Call your vet if your horse:
| Sign | Why it matters |
|---|---|
| Stops eating | Older horses can decline quickly |
| Develops colic signs | Needs urgent assessment |
| Becomes dull or depressed | Could be medication related or another illness |
| Has laminitis signs | Emergency risk |
| Cannot take medication reliably | Treatment plan needs adjustment |
Diet Monitoring: Not Every PPID Horse Needs the Same Feed
This is one of the biggest owner misunderstandings.
Not every PPID horse needs aggressive carbohydrate restriction. Some PPID horses are overweight with insulin dysregulation. Others are lean, older, losing muscle, and need more calories, protein, and senior nutrition support.
The Equine Endocrinology Group states that feed selection in PPID horses should be based on body condition and whether insulin dysregulation is present. Horses with PPID and insulin dysregulation require lower nonstructural carbohydrate feeds and limited pasture access, but PPID horses with normal insulin regulation confirmed by dynamic testing do not automatically need a carbohydrate restricted diet. (Squarespace)
That means the diet plan should be built around the horse in front of you.
| Horse type | Diet focus |
|---|---|
| Overweight PPID horse with high insulin | Low NSC forage, pasture restriction, controlled calories |
| Lean PPID horse with muscle loss and normal insulin | Adequate calories, quality protein, fat if needed, senior feed support |
| PPID horse with laminitis history | Strict insulin and pasture management |
| PPID horse with poor teeth | Soaked feeds, chopped forage, senior ration, dental support |
| PPID horse with normal insulin and good condition | Balanced maintenance diet, not unnecessary restriction |
The mistake is feeding every PPID horse like a fat pony on spring grass. Some are. Some are not.
PPID, Insulin, and Laminitis Risk
Laminitis is the complication that keeps vets awake, and not in the fun “late night coffee” way.
PPID horses should be assessed for insulin dysregulation because laminitis risk increases when insulin regulation is abnormal. MSD Veterinary Manual states that if insulin dysregulation is present, horses with PPID are at high risk for laminitis. (MSD Veterinary Manual)
Monitor closely for:
| Laminitis warning sign | What to do |
|---|---|
| Heat in the feet | Call your vet if persistent or paired with pain |
| Strong digital pulses | Treat seriously, especially in high risk horses |
| Reluctance to walk | Possible active laminitis |
| Short pottery steps | Early foot pain clue |
| Difficulty turning | Common laminitis sign |
| Shifting weight | Pain in the feet |
| Rocked back stance | More serious laminitis concern |
| New hoof rings | May indicate previous laminitic stress |
A PPID horse with new foot soreness should be treated as laminitis until proven otherwise.
What Else Can Look Like PPID?
Not every older horse with weight loss, poor coat, or reduced energy has PPID alone.
Important rule outs include:
| Condition | Why it can look similar |
|---|---|
| Equine metabolic syndrome | Obesity, cresty neck, insulin dysregulation, laminitis risk |
| Dental disease | Weight loss, poor condition, quidding, feed dropping |
| Chronic pain | Muscle loss, reduced performance, behavioural change |
| Parasite burden | Weight loss, poor coat, poor condition |
| Chronic infection | Weight loss, lethargy, abnormal bloodwork |
| Liver or kidney disease | Weight loss, dullness, drinking changes |
| Poor nutrition | Muscle loss, poor coat, low energy |
| True thyroid disease | Rare in adult horses, often over suspected |
| Normal ageing | Some muscle and coat changes overlap, but should not be assumed |
| Cancer or chronic inflammatory disease | Weight loss or decline despite feeding |
The real clinical question is not “does this old horse have PPID?”
It is: what problems does this horse have, and which ones are actually driving the risk?
PPID can be part of the story without being the whole story.
When Is This an Emergency?
PPID itself is usually chronic, but PPID horses can develop urgent complications.
Call your vet urgently if your horse has:
| Red flag | Why it matters |
|---|---|
| Reluctance to move | Possible laminitis |
| Heat in the feet with strong digital pulses | Possible active laminitis |
| Shifting weight or rocked back stance | Serious foot pain |
| Sudden severe lameness | Laminitis, abscess, fracture, or other urgent problem |
| Not eating after pergolide or dose change | Medication issue, colic, dental pain, or systemic illness |
| Colic signs | Needs prompt assessment |
| Fever or severe dullness | Possible infection or systemic disease |
| Wound that becomes swollen, hot, painful, or infected | PPID horses may have reduced immune resilience |
| Eye pain, squinting, or cloudiness | Horse eyes can deteriorate quickly |
| Collapse, severe weakness, or inability to rise | Emergency |
The decision point is simple: do not treat laminitis signs, severe infection, eye pain, or sudden appetite loss as routine PPID monitoring. Those are vet now problems.
What To Do Right Now If Your Horse Has PPID
1. Build a monitoring sheet
Record body condition, weight tape, appetite, coat shedding, muscle, drinking, urination, hoof changes, medication dose, and any laminitis signs.
2. Ask your vet about ACTH timing
Test timing matters. Ask when ACTH should be checked in your region and whether you should compare results in the same season each year.
3. Test insulin, not just ACTH
Insulin status changes laminitis risk and diet planning. PPID without insulin dysregulation is managed differently from PPID with high insulin.
4. Review diet based on body condition
Do not automatically restrict every PPID horse. Lean older horses may need more calories and protein, while insulin dysregulated horses need stricter carbohydrate and pasture control.
5. Schedule farrier care
Hoof monitoring is part of PPID monitoring, especially if there has ever been laminitis, hoof rings, footiness, or strong digital pulses.
6. Check teeth and parasite control
Dental disease and parasite issues can make PPID horses look worse and can be mistaken for poor endocrine control.
7. Watch appetite after pergolide changes
Reduced appetite may be temporary, but persistent inappetence should be discussed with your vet.
8. Recheck if signs do not match the bloodwork
If the ACTH improves but the horse still looks terrible, keep looking. Pain, teeth, infection, parasites, poor nutrition, kidney disease, liver disease, or another condition may be involved.
Common Mistakes Owners Make
Mistake 1: Monitoring ACTH but ignoring insulin
ACTH helps monitor PPID. Insulin helps assess laminitis risk. You need both in many horses.
Mistake 2: Assuming a long coat is the only important sign
The coat is visible, but laminitis, infections, dental disease, muscle loss, and poor body condition may matter more.
Mistake 3: Starving a lean PPID horse
A thin old horse with PPID and normal insulin may need better nutrition, not stricter restriction.
Mistake 4: Treating PPID but missing EMS
A horse can have PPID and insulin dysregulation. Pergolide may help PPID, but diet and insulin management still matter.
Mistake 5: Increasing pergolide based only on one ACTH result
Season, breed, clinical signs, lab method, stress, and overall response all matter. Dose changes should be interpreted in context.
Mistake 6: Stopping pergolide because the horse looks better
PPID has no true cure. UC Davis notes that treatment is intended to reduce clinical signs and must continue for life. (Center for Equine Health)
Mistake 7: Ignoring appetite changes
Pergolide associated inappetence can happen. Do not just push through if the horse is not eating.
Mistake 8: Replacing treatment with supplements
The Equine Endocrinology Group states that dietary supplements have been suggested for PPID management, but scientific evidence for their efficacy is lacking. (Squarespace)
Long Term Care for Horses With PPID
PPID monitoring is whole horse care.
A long term plan should include:
| Care area | Why it matters |
|---|---|
| Pergolide review | Ensures treatment still fits the horse |
| ACTH monitoring | Tracks endocrine response over time |
| Insulin testing | Protects against laminitis risk |
| Diet review | Adjusts for weight, teeth, insulin, muscle, and age |
| Hoof care | Detects laminitis and chronic hoof changes early |
| Dental care | Older horses often need feeding plans changed |
| Parasite control | PPID horses may need careful monitoring |
| Vaccination | Immune resilience may be reduced |
| Wound checks | Poor healing can signal poor control or infection |
| Coat clipping | Helps comfort in long coated horses |
| Heat management | Long coats and sweating changes can affect comfort |
| Quality of life review | Keeps decisions centred on the horse, not just blood results |
MSD Veterinary Manual emphasises that good husbandry is essential in PPID horses, including regular farriery, dental care, and parasite management. UC Davis also highlights preventative veterinary care, dental examinations, periodic bloodwork, vaccination, deworming, and farrier work as important parts of PPID management. (MSD Veterinary Manual)
Monitoring Checklist for Owners
Use this as a simple monthly PPID review.
| Question | Why it matters |
|---|---|
| Is the coat shedding better, worse, or unchanged? | Tracks clinical response |
| Is the horse losing muscle? | May indicate PPID, age, nutrition, pain, or another disease |
| Has the appetite changed? | Important with pergolide and senior health |
| Is the horse drinking or urinating more? | PPID sign, but also other disease possible |
| Are the feet warm or pulses stronger? | Laminitis warning |
| Is the horse moving differently? | Early foot pain or other lameness |
| Is body condition changing? | Guides diet adjustment |
| Is the neck crest changing? | Insulin risk clue |
| Are wounds healing normally? | Immune and endocrine control clue |
| Any infections, abscesses, or dental problems? | PPID horses need proactive care |
| Any missed medication doses? | Helps interpret worsening signs |
| When is the next ACTH and insulin check due? | Keeps monitoring proactive |
The best monitoring system is the one you actually use. A simple notebook beats an imaginary perfect spreadsheet every day of the week.
Can PPID Horses Still Have a Good Life?
Yes. Many horses with PPID can live comfortably for years with good management.
The Equine Endocrinology Group states that most owners of PPID positive horses report good quality of life, and PPID does not necessarily reduce life span. The caution is that most affected horses are older, so age related health problems still need attention. (Squarespace)
The outlook is better when:
| Good sign | Why it helps |
|---|---|
| Diagnosis is made before severe laminitis | Prevention is easier than repair |
| Pergolide response is monitored | Treatment can be adjusted |
| Insulin is tested | Laminitis risk is clearer |
| Diet matches the horse | Avoids both overfeeding and underfeeding |
| Hoof care is regular | Subtle laminitis changes are caught earlier |
| Teeth are maintained | Supports weight and nutrition |
| Appetite stays good | Reduces senior horse decline risk |
| Owner notices small changes early | Small problems are easier to fix |
The outlook becomes more guarded when there is repeated laminitis, uncontrolled insulin, severe weight loss, recurrent infections, poor appetite, severe dental disease, or poor response despite appropriate treatment.
Related Horse Health Topics To Link Internally
This article fits naturally with:
| Related topic | Why it connects |
|---|---|
| How To Prevent Founder in Horses | Laminitis is one of the biggest PPID risks |
| Equine Metabolic Syndrome in Horses | EMS and PPID can overlap |
| Insulin Dysregulation in Horses | Insulin drives much of the laminitis risk |
| Thyroid Supplements for Horses | Often discussed in overweight metabolic horses |
| Corneal Ulcers in Horses With PPID | PPID and age may affect corneal health and healing |
| Senior Horse Weight Loss | PPID, teeth, nutrition, pain, and disease can overlap |
FAQs About Monitoring PPID in Horses
How often should a horse with PPID have ACTH checked?
Many horses are rechecked 1 to 3 months after starting pergolide, then every 6 to 12 months once stable. Higher risk horses, horses with persistent signs, or horses with laminitis risk may need more frequent monitoring. (Squarespace)
Should insulin be tested in every horse with PPID?
Insulin assessment is strongly recommended because PPID is often accompanied by insulin dysregulation, and insulin dysregulation increases laminitis risk. Diet and pasture recommendations depend heavily on insulin status. (Squarespace)
Does a normal ACTH test rule out PPID?
Not always. Cornell notes that normal results on commonly used PPID tests do not fully preclude the presence of a pituitary adenoma. The horse’s signs, age, season, and repeat or dynamic testing may still matter. (Cornell Vet College)
How quickly should pergolide improve signs?
Clinical signs may begin improving within 1 to 3 months, but response varies. Coat changes can take longer because they depend on hair growth and shedding cycles. UC Davis notes that clinical signs should show improvement within 1 to 3 months. (Center for Equine Health)
Can PPID be cured?
No. PPID is managed, not cured. Treatment is usually lifelong and focuses on controlling signs, reducing complications, monitoring insulin risk, and supporting quality of life. (Center for Equine Health)
The Bottom Line
Monitoring Cushing’s disease in horses is not just about chasing an ACTH number.
A good PPID plan monitors the whole horse: coat, appetite, muscle, body condition, feet, insulin, laminitis signs, infections, teeth, medication response, and quality of life. ACTH testing matters, but it must be interpreted with season, breed, clinical signs, stress, and the horse’s overall health.
The most important rule is this: a stable PPID horse needs routine monitoring, but a PPID horse with foot pain, strong digital pulses, sudden appetite loss, severe infection, eye pain, or colic signs needs urgent veterinary attention.
Manage the endocrine disease, but do not forget the horse living inside it.
If you are unsure whether your horse’s PPID is well controlled, whether insulin testing is needed, or whether changes in appetite, hooves, weight, or behaviour are urgent, ASK A VET™ can help you understand what signs matter and when veterinary care is needed.