📋 At a Glance
⚠️ Signs Requiring Veterinary Contact
- An abnormally long, curly, or wavy coat — especially if the horse fails to shed in spring
- Progressive muscle wasting along the topline resulting in hollow back and prominent spine despite feeding
- Recurrent or unexplained laminitis in a horse over 10 — even without an obvious dietary trigger
- Significant pot-bellied appearance from abdominal muscle loss
- Markedly increased water consumption and urination in an older horse
- Increased fat deposits, particularly above the eyes (supraorbital fat pads) and along the crest of the neck
- Recurrent infections — skin conditions, sinusitis, dental infections — that may reflect immune suppression
What Is PPID — How Does It Develop?
The pituitary gland sits at the base of the brain and controls many hormonal systems. In horses with PPID, the pars intermedia region of the pituitary undergoes pathological hypertrophy and hyperplasia — producing excessive amounts of POMC-derived peptides including ACTH (adrenocorticotropic hormone). Elevated ACTH drives the adrenal glands to produce excess cortisol, which in turn suppresses immune function, promotes muscle catabolism, and disrupts insulin signaling.
PPID is a progressive, age-related neurodegenerative condition — it is not caused by anything the owner did or didn't do. The dopamine-producing neurons that normally suppress the pars intermedia undergo oxidative damage over time, allowing this region of the pituitary to expand unchecked. It is not curable, but it is highly manageable — most horses on appropriate pergolide treatment show significant improvement in clinical signs within weeks to months.
PPID and Laminitis — A Critical Connection
The most important clinical consequence of PPID — and the one most likely to be life-threatening — is laminitis. Horses with PPID develop insulin dysregulation that drives lamellar inflammation even on diets that would be perfectly safe for a metabolically normal horse. This is why laminitis in older horses deserves ACTH testing even when an obvious dietary trigger is not present.
Early PPID diagnosis and treatment with pergolide has been shown to reduce laminitis frequency and severity in affected horses — making early detection genuinely life-saving. The horse that develops its first unexplained laminitis episode at age 15 is very likely to have PPID driving it, and treatment changes the long-term trajectory.
Diagnosis — Testing and Interpretation
PPID is diagnosed through blood testing. The standard test measures plasma ACTH concentration — a single blood sample drawn from the jugular vein, ideally in the morning after a short fast. Results are compared to reference ranges that are adjusted for season: ACTH levels have a normal physiological rise from approximately August through October in the Northern Hemisphere, and horses that test borderline during this period may need retesting in spring for clarification.
| Test | What It Measures | When To Use | Notes |
|---|---|---|---|
| Resting ACTH | Baseline plasma ACTH concentration | First-line screening for all horses with clinical signs or over age 15 | Seasonal reference ranges required; October testing needs adjustment |
| TRH Stimulation Test | ACTH response to thyrotropin-releasing hormone injection 10 minutes after baseline | When resting ACTH is borderline but clinical suspicion is high | More sensitive than resting ACTH; can detect earlier PPID |
| Insulin/glucose | Fasting insulin; glucose:insulin ratio | To assess concurrent EMS; to evaluate laminitis risk | High insulin with PPID significantly increases laminitis risk |
Treatment and Monitoring
Pergolide (Prascend) is the primary medication for PPID management — a dopamine agonist that suppresses pars intermedia over-activity and reduces excess ACTH production. It is administered daily as an oral medication (tablets that can be crushed or administered whole). Most horses require lifelong treatment, typically starting at 0.002 mg/kg once daily and adjusted based on clinical response and retesting.
Response to treatment is assessed clinically (coat shedding, muscle condition, water intake, laminitis episodes) and with repeated ACTH measurement. Annual retesting is the minimum; horses being actively managed through a laminitis episode or dose adjustment may need testing every 3 months. PPID is progressive — doses typically need to be increased over time as the disease advances.
What to Monitor on Pergolide Treatment
- ACTH level at 4–6 weeks after starting or dose change — confirms therapeutic suppression
- Clinical signs over 8–12 weeks — coat quality, muscle condition, water intake, energy level
- Annual dental exam — PPID horses are prone to accelerated dental disease
- Body weight and condition monthly — catch weight loss early
- Laminitis vigilance — even treated horses have elevated risk during grazing season
Senior Horse Care with PPID
Horses with PPID often have additional senior health concerns that compound the management complexity. Dental disease accelerates in PPID horses, often requiring more frequent dental exams (every 6 months rather than annual). Immune suppression increases susceptibility to skin infections, sinusitis, and parasite burdens. The combination of muscle wasting, dental difficulty, and metabolic disruption makes nutritional management challenging.
A team approach — equine veterinarian, farrier with laminitis experience, and an engaged owner — produces the best long-term outcomes for PPID horses. Many horses with PPID can continue comfortable, productive lives well into their twenties with appropriate management.
✅ Action Steps — While Contacting Your Vet
- Schedule an ACTH blood test with your veterinarian — if your horse is over 10 and has any clinical signs, test soon; if over 15, test annually regardless of signs
- Photograph the coat — photos over time document coat quality changes and response to treatment objectively
- Start dietary management immediately if PPID is suspected — restrict grass access and reduce dietary NSC while awaiting test results
- Ask about insulin testing concurrently — knowing whether insulin dysregulation is present determines laminitis risk level
- Discuss pergolide starting dose and the retesting timeline with your veterinarian — typically 4–6 weeks after starting
📋 Prevention & Long-Term Management Discussion Points
- Annual ACTH testing even in treated horses — PPID is progressive and dose requirements increase over time
- Seasonal testing timing — ideally spring (February–June) for baseline; if testing in fall, ask your vet to apply seasonal correction
- Insulin testing — if insulin is elevated alongside PPID, dietary restrictions and laminitis monitoring become more aggressive
- Dental examination every 6 months for PPID horses — accelerated periodontal disease is common
- Low-NSC hay and pasture management — even treated horses need dietary management during spring and fall grass surges
- Fly and skin infection management — immune suppression increases susceptibility
Questions to Ask Your Veterinarian
- What is this horse's ACTH level, and does it fall within or above the seasonal reference range?
- Should we also test resting insulin to assess concurrent EMS and laminitis risk?
- What starting dose of pergolide do you recommend, and when should we retest?
- What are the signs of adequate PPID control that I should be watching for?
- Given this horse's ACTH and insulin levels, what specific dietary restrictions do you recommend for pasture and hay NSC?
- How often should dental exams be scheduled, and are there diet adjustments needed for this horse's current dental condition?
