PPID review reinforces testing and lifelong management in horses

Version 2

A newly indexed review on pituitary pars intermedia dysfunction, or PPID, brings fresh attention to a familiar but still clinically challenging disease in equine practice. In The Veterinary Clinics of North America: Equine Practice, Sarah A. Vaughn and Kelsey A. Hart describe PPID as one of the most common equine endocrine disorders and frame it around a now well-established pathophysiology: oxidative injury to hypothalamic dopaminergic neurons, loss of inhibition of the pars intermedia, and increased secretion of ACTH and related peptides. (madbarn.com)

That overview lands at a time when the field has already been moving toward more structured, evidence-based guidance. In 2024, BEVA published primary care clinical guidelines on diagnosis and management of equine PPID, reflecting a broader push to standardize how veterinarians test, treat, and monitor affected horses. Those guidelines emphasize that diagnosis should not rely on laboratory values alone, but instead combine history, clinical signs, and endocrine testing, especially because test performance and interpretation can be influenced by season, disease stage, and concurrent metabolic disease. (beva.onlinelibrary.wiley.com)

The core clinical message from the new review is consistent with that direction. Resting ACTH and TRH-stimulated ACTH remain the principal diagnostic tools, while assessment of insulin regulation is important because insulin dysregulation may coexist with PPID and materially change laminitis risk and case management. Merck’s veterinary references similarly note that PPID is not curable, but daily pergolide can reduce clinical signs and lower laminitis risk, and they flag overlap with equine metabolic syndrome in older horses. (madbarn.com)

Research and practice guidance continue to show why diagnosis is rarely as simple as a single blood draw. Cornell-associated data and other expert resources have long documented a seasonal rise in ACTH, particularly from August through October in North America, which means reference intervals and interpretation matter. BEVA’s guideline goes further, noting that while endocrine assays are widely used to monitor response to pergolide, evidence remains limited on whether titrating treatment around those hormone values alone improves outcomes. The same guideline also suggests there is little advantage in waiting more than a month for follow-up endocrine testing after treatment initiation, and possibly some merit in testing sooner. (pubmed.ncbi.nlm.nih.gov)

On treatment, the standard of care remains stable. Pergolide mesylate is still the drug of choice, and the FDA-approved equine product, Prascend, remains labeled in the U.S. for control of clinical signs associated with PPID in horses under NADA 141-331. DailyMed lists the currently marketed product as 1 mg pergolide tablets from Boehringer Ingelheim Animal Health USA. Across clinical references, reduced appetite and listlessness remain among the adverse effects practitioners are most likely to discuss with pet parents and barn managers when starting therapy. (dailymed.nlm.nih.gov)

Expert commentary in the formal sense was limited in the publicly accessible material tied directly to this review, but the broader industry conversation is clear: PPID management is increasingly centered on earlier recognition, better use of dynamic testing, and more deliberate monitoring for insulin dysregulation and laminitis. AAEP educational materials and recent proceedings continue to reflect active discussion over practical questions, including ideal TRH-stimulation timing and how to interpret borderline or seasonally influenced ACTH results in real-world practice. (aaep.org)

Why it matters: For veterinary professionals, this review doesn’t announce a new drug or a practice-changing trial, but it does consolidate the current clinical consensus around a disease many ambulatory equine practitioners manage routinely. The biggest takeaway is that PPID care is increasingly about nuance: choosing the right test, interpreting it in context, screening for concurrent insulin dysregulation, counseling pet parents about lifelong therapy, and keeping laminitis prevention front and center. In that sense, the review is less a disruption than a timely checkpoint for evidence-aligned care. (madbarn.com)

What to watch: The next developments are likely to come not from a wholesale rethink of PPID, but from refinements in diagnostic thresholds, seasonal reference intervals, dynamic test protocols, and evidence on whether hormone-guided pergolide adjustments translate into better clinical outcomes. (beva.onlinelibrary.wiley.com)