New PPID data sharpen prognosis and monitoring questions
Bottom line
Pituitary pars intermedia dysfunction, or PPID, remains a common and evolving clinical challenge in older horses, and recent coverage is sharpening two practical points for veterinarians: prognosis may be better than many pet parents expect, but disease management is still medically intensive. EquiManagement highlighted new research showing horses with PPID did not have shorter life expectancies than matched controls, even though they experienced more medical events over time. The same report also underscored uncertainty around monitoring treated horses, noting that pergolide can blunt ACTH responses on thyrotropin-releasing hormone, or TRH, stimulation testing without clearly mirroring clinical improvement. Meanwhile, The Horse focused on a day-to-day management issue many clinicians see in practice: the hard-keeping PPID horse that needs more calories without increasing laminitis risk. (equimanagement.com)
Why it matters: For equine practitioners, the takeaway is that PPID care is less about a single lab value and more about longitudinal management. Current guidance and recent reviews emphasize pairing endocrine testing with clinical signs, screening for insulin dysregulation because of its overlap with laminitis risk, and adjusting nutrition, dental care, and general supportive care as horses age. That’s especially relevant for thin PPID horses, where adding calories safely often means relying on low-nonstructural-carbohydrate forage strategies and individualized ration changes rather than simply increasing starch intake. (beva.onlinelibrary.wiley.com)
What to watch: Expect continued scrutiny of how veterinarians should use TRH stimulation testing in pergolide-treated horses, and more emphasis on practical monitoring strategies that combine lab trends with body condition, laminitis history, and clinical response. (equimanagement.com)
Key facts
- Condition
- Pituitary pars intermedia dysfunction (PPID)
- Population
- Older horses
- Prevalence
- About 20% of horses older than 15 develop PPID
- Study design
- Retrospective Purdue study
- Sample size
- 132 horses with PPID, 274 matched controls
- Study period
- 1996 to 2024
- Main finding
- Horses with PPID did not have shorter life expectancies than matched controls
- Treatment/testing issue
- Pergolide can blunt ACTH responses on TRH stimulation testing without clearly mirroring clinical improvement
- Management issue
- Thin PPID horses may need more calories without increasing laminitis risk
Pituitary pars intermedia dysfunction is already one of the most familiar endocrine diagnoses in older horses, but new reporting and recent literature suggest the clinical conversation is shifting. The latest message for veterinarians is more nuanced than simply “diagnose and treat with pergolide”: horses with PPID may live as long as similar non-PPID horses, yet they accumulate more medical issues along the way, and some commonly used endocrine follow-up tests may not track neatly with clinical improvement. (equimanagement.com)
That matters because PPID is common in aging equids. EquiManagement reported that about 20% of horses older than 15 develop PPID, and a recent review described the disorder as a neurodegenerative endocrine disease affecting roughly 15% to 30% of aged horses and ponies. The disease stems from loss of dopaminergic inhibition of the pars intermedia, driving excess ACTH and related peptides. Diagnosis still centers on resting ACTH and TRH-stimulated ACTH, but interpretation is complicated by season, assay choice, handling, stress, age, breed, and concurrent illness. (equimanagement.com)
One of the most consequential updates is the prognosis data. EquiManagement summarized a retrospective Purdue study of 132 horses with PPID and 274 matched controls, based on records from 1996 to 2024. In that cohort, horses with PPID had more medical events overall than controls, and more events after diagnosis than before, but they did not have shorter life expectancies. Surviving PPID horses were older than surviving controls, and median age at euthanasia was similar between groups. A related report in The Horse said the study was published in JAVMA in March 2026, reinforcing the idea that a PPID diagnosis should not automatically be framed as a short-term prognosis discussion with pet parents. (equimanagement.com)
At the same time, PPID’s overlap with insulin dysregulation remains central to case management. EquiManagement reported that nearly 77% of horses with PPID also develop insulin dysregulation, while BEVA’s primary care guideline stresses that horses presenting with laminitis, abnormal fat distribution, or other overlapping signs should be evaluated for insulin dysregulation as well as PPID. That overlap helps explain why nutrition remains such a persistent challenge, especially in thin older horses with a laminitis history. In The Horse’s recent management piece, the practical question was how to safely increase calories in a 25-year-old hard-keeping gelding with PPID without worsening metabolic risk. (equimanagement.com)
The testing question may be the most immediately practice-changing. EquiManagement summarized prior and recent work suggesting pergolide lowers ACTH concentrations before and after TRH stimulation, but that normalization of test results does not necessarily align with visible clinical improvement. In the article’s summary of a recent German study, there were no significant differences in baseline or 10-minute post-TRH ACTH values between horses that improved clinically on pergolide and those that did not, leading the authors to caution against relying too heavily on TRH stimulation testing alone for dose adjustment. Supporting literature also suggests pergolide affects baseline ACTH more than post-TRH ACTH in some settings, which adds to the uncertainty around how best to interpret repeat testing in treated horses. (equimanagement.com)
Industry and guideline perspectives are converging on a more practical, whole-horse approach. BEVA guidance indicates pergolide can improve clinical signs such as hypertrichosis, lethargy, muscle wastage, and laminitis in a proportion of treated cases, but it also emphasizes that laboratory testing should be interpreted within the broader clinical picture. Recent nutrition guidance likewise recommends regular reassessment for insulin dysregulation in aging PPID horses and recognizes that maintaining body condition can become harder over time because of age-related changes, dentition issues, and seasonal energy demands. That aligns with The Horse’s emphasis on individualized feeding plans for hard keepers rather than one-size-fits-all restriction. (beva.onlinelibrary.wiley.com)
Why it matters: For veterinary professionals, this is a reminder that PPID is increasingly a chronic-care workflow issue, not just an endocrine diagnosis. Practices managing older horses will likely need structured follow-up that includes endocrine monitoring, insulin assessment, laminitis surveillance, dentistry, nutrition review, and candid conversations with pet parents about quality of life and treatment goals. The newer survival data may support more balanced counseling, while the TRH-pergolide findings argue for caution when making medication changes based on laboratory response alone. Inference: the standard of care is moving toward integrated management, where body condition, hoof health, and day-to-day function may be as important as whether a post-TRH ACTH value normalizes. (equimanagement.com)
What to watch: The next phase of PPID research will likely focus on how best to monitor treated horses in primary care, including whether repeat TRH stimulation testing, resting ACTH trends, insulin markers, or clinical scoring systems offer the most useful guidance over time. Newer primary-care outcome data published in 2026 may help refine that picture further, especially around which horses are most likely to improve after diagnosis and treatment. (pubmed.ncbi.nlm.nih.gov)