27/08/2025
EMS, PPID, IR, HAL – SORTING OUT THE METABOLIC MINEFIELD
The language around metabolic laminitis is a mess. Insulin resistance, Cushing’s, metabolic syndrome, hyperinsulinaemia—it’s not always clear where one ends and another begins. But these terms matter, because they guide testing, treatment, and long-term management.
Here’s a breakdown of the four most commonly used terms—EMS, PPID, IR, and HAL—how they differ, where they overlap, and what that means for your horse.
A NOTE ON PATTERNS – AND EXCEPTIONS
The profiles below reflect common patterns, not hard rules. Yes, EMS usually shows up in younger horses. Yes, PPID tends to appear in those over 15. But horses don’t read textbooks.
• PPID has been diagnosed in horses as young as 7
• EMS can persist into old age
• Hyperinsulinemia doesn’t always come with fat pads or distortion of the white line.
So treat patterns as helpful—not as diagnostic gates.
1. INSULIN RESISTANCE (IR)
What it is: A mechanism, not a diagnosis. The horse’s tissues stop responding properly to insulin, so the body produces more. The result is chronic hyperinsulinaemia.
Typical age: Any age—including young horses.
Risk factors:
• Easy keepers
• Low movement
• Rich forage
• Stress
• Genetic predisposition
Signs:
• Regional fat pads (crest, shoulders, tailhead)
• “Footy on hard ground”
• Hoof distortion (flare, stretched white line)
• Sudden or unexplained laminitis
Management focus:
• Remove high-sugar/starch feeds
• Encourage movement
• Reduce stress
• Support weight loss only if needed
• Use insulin testing
Note: IR is not a diagnosis. It’s part of EMS, PPID, or both—or it may precede either.
2. EQUINE METABOLIC SYNDROME (EMS)
What it is: A clinical syndrome characterised by insulin dysregulation. Often reversible.
Typical age: Typically 5–15 (but can appear earlier or later)
Risk factors:
• Native and cob types
• Chronic overfeeding
• Lack of movement
• Inflammatory load
Signs:
• Cresty neck, fat pads
• Reluctance on hard ground
• Toe-first landings, hoof distortion
• Radiographic changes before clinical pain
• Sudden laminitis without warning
Management focus:
• Tight control of forage and calories
• Restore movement gradually
• Cut unnecessary supplements
• Test insulin
Note: EMS can improve dramatically—but not if ignored.
3. PITUITARY PARS INTERMEDIA DYSFUNCTION (PPID)
What it is: A progressive neurodegenerative disease that disrupts hormone regulation (especially ACTH).
Typical age: Usually 15+, but has been diagnosed in horses as young as 7.
Risk factors:
• Ageing horses
• Especially geldings
• Pain, chronic stress, past injuries
Signs:
• Delayed shedding / long or curly coat (often a late-stage sign)
• Muscle wastage (topline, glutes)
• Lethargy, dullness, or behaviour changes
• Drinking/urinating more
• Recurrent infections (skin, hooves, sheath)
• Suspensory ligament breakdown
• +/- insulin dysregulation
Important: It’s a common misconception that PPID = hairy coat. In reality, many horses—especially in earlier stages—shed normally or just slightly late. If coat changes are the only thing we’re looking for, we’ll miss many cases until complications like laminitis or immune dysfunction appear.
Management focus:
• Pergolide (Prascend®) to regulate hormone production
• Seasonally adjusted ACTH testing (especially in autumn)
• If insulin is elevated: manage concurrently as EMS
• Dietary control, stress reduction, and proactive hoof care
CAN YOU MANAGE PPID WITHOUT MEDICATION?
Technically yes—but not effectively or safely in most cases.
PPID is progressive. Once dopaminergic neurons are lost, nothing restores their function—except pergolide. No supplement or management plan can suppress ACTH the way this drug does.
What about herbs?
Chasteberry, ashwagandha, milk thistle, and various “pituitary support” blends have no robust scientific support.
One small study showed short-term coat improvement with chasteberry but no ACTH suppression
Pergolide was significantly more effective in every head-to-head trial
No herbal product reduces laminitis risk or slows disease progression
Bottom line: Herbs are not alternatives. At best, they’re adjuncts. At worst, they delay treatment.
4. HYPERINSULINAEMIA-ASSOCIATED LAMINITIS (HAL)
What it is: Laminitis caused directly by high insulin levels—regardless of the underlying condition.
Typical age: Any. Seen in young ponies, middle-aged horses, and seniors alike.
Risk factors:
• Any horse with insulin dysregulation
• Horses under stress
• Sudden diet changes
• Box rest or inactivity
Signs:
• Laminitis with no obvious dietary trigger
• Painful or “silent” events
• May occur after weather shifts, pain, turnout, or medication change
Management focus:
• Restrict diet immediately
• Reduce insulin fast
• Provide hoof support and rest
• Monitor long-term insulin status
Note: If insulin is elevated and laminitis is present—it’s HAL, no matter the label.
SUMMARY – HOW THE TERMS COMPARE
INSULIN RESISTANCE (IR)
Type: Mechanism
Age: Any
Risk: Genetics, diet, stress
Reversible? Yes
Laminitis risk: Yes, if insulin is high
EQUINE METABOLIC SYNDROME (EMS)
Type: Syndrome
Age: Typically 5–15
Risk: Native types, lifestyle mismatch
Reversible? Often
Laminitis risk: Yes
PITUITARY PARS INTERMEDIA DYSFUNCTION (PPID)
Type: Disease
Age: Typically 15+, but can be younger
Risk: Neurodegeneration, stress
Reversible? No (progressive)
Laminitis risk: Only if insulin is also dysregulated
HYPERINSULINAEMIA-ASSOCIATED LAMINITIS (HAL)
Type: Mechanism
Age: Any
Risk: Any insulin-spiking event (diet, stress, pain)
Reversible? N/A
Laminitis risk: Always
INSULIN TESTING IN HORSES – FASTING VS. FED
Contrary to common assumption, insulin testing in horses is usually done unfasted.
Why?
Because insulin dysregulation is a problem of response — not just baseline levels.
We want to see how the horse handles sugar intake, not how it behaves in a metabolically quiet state.
FOR MOST HORSES, THIS MEANS:
No fasting overnight
Offer a flake of low-sugar hay 4–6 hours before the test
In some protocols, a small amount of soaked hay or fibre feed is given 1–2 hours before blood draw (ask your vet)
DYNAMIC TESTING (e.g. ORAL SUGAR TEST):
Involves giving Karo syrup or dextrose
Measures insulin response after a sugar challenge
More sensitive than resting insulin alone
Helps detect early or borderline cases
WHY FASTING IS RISKY OR MISLEADING:
Fasting can lower insulin artificially, masking early dysregulation
Some horses (e.g. with ulcers or laminitis risk) should never be fasted
Fasting doesn’t reflect real-life responses to normal forage intake
BOTTOM LINE:
Unless your vet specifies otherwise, most insulin testing should be done with recent hay on board.
We’re not looking for a flatline — we’re looking for how the system reacts.
FINAL THOUGHTS
Don’t assume a 12-year-old can’t have PPID
Don’t guess insulin status—test it
Don’t treat neurodegeneration with herbs
Don’t wait for obvious symptoms—many of these horses look “fine”… until they’re not
Because laminitis isn’t just about the hoof.
It starts with hormones—and it ends with what we do (or don’t) manage.
