BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction.
Authors: Menzies-Gow Nicola J, Banse Heidi E, Duff Aimi, Hart Nicholas, Ireland Joanne L, Knowles Edward J, McFarlane Dianne, Rendle David
Journal: Equine veterinary journal
Summary
# BEVA Guidelines on Equine PPID: Evidence-Based Diagnosis and Management The British Equine Veterinary Association convened a multidisciplinary panel to develop evidence-based primary care guidelines for pituitary pars intermedia dysfunction (PPID), a prevalent age-related condition affecting 21–27% of horses aged 15 years and above. Using the rigorous GRADE framework, researchers systematically reviewed published literature across four key areas: case selection and diagnostic test accuracy, test result interpretation, pharmacological treatment options, and post-treatment monitoring. The analysis revealed that basal adrenocorticotropic hormone (ACTH) testing demonstrates 88–92% diagnostic accuracy in autumn but only 70–86% outside this window, whilst TRH-stimulated ACTH testing achieves superior sensitivity (90–98%) with less seasonal variation—emphasising that pre-test probability, breed, location, diet and coat colour significantly influence interpretation. Pergolide remains the only evidence-supported pharmacological intervention, effectively improving clinical signs and lowering ACTH concentrations in most horses, though it does not correct insulin dysregulation; conversely, chasteberry supplementation and cyproheptadine offer no additional benefit. Whilst no standardised monitoring protocol demonstrates improved clinical outcomes, the guidelines highlight substantial gaps in current knowledge regarding optimal ACTH threshold ranges, the clinical significance of insulin dysregulation in PPID cases, compliance rates with lifelong therapy, and the relevance of increased parasite shedding—underscoring the need for clinical practitioners to integrate diagnostic findings with age, clinical presentation and pre-test probability to avoid unnecessary lifelong treatment and missed diagnoses.
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Practical Takeaways
- •Consider age (≥15 years), hypertrichosis, and delayed hair shedding as primary indicators for PPID testing; use TRH stimulation testing for improved diagnostic accuracy over basal ACTH alone, especially outside autumn months
- •Recognize that breed and seasonal factors substantially influence ACTH values—interpret results using equivocal ranges and pre-test probability rather than fixed cutoffs to avoid false positive diagnoses and unnecessary lifelong therapy
- •Start pergolide treatment based on clinical signs and diagnostic results; monitor clinical improvement rather than strictly chasing ACTH values, as hormone levels may normalize without full clinical resolution and compliance with treatment is often poor
Key Findings
- •PPID prevalence in horses aged ≥15 years is 21-27%; basal ACTH diagnostic accuracy ranges 88-92% in autumn and 70-86% in non-autumn depending on pre-test probability
- •TRH stimulation testing shows superior diagnostic accuracy (92-98% in autumn, 90-94% in non-autumn) compared to basal ACTH testing
- •Pergolide improves most clinical signs and lowers basal ACTH in majority of affected horses, but does not alter insulin dysregulation measures in most cases
- •Multiple factors including breed, latitude, diet, and coat colour significantly affect ACTH concentrations, requiring use of equivocal diagnostic ranges rather than fixed thresholds