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Pituitary Pars Intermedia Dysfunction (PPID) represents the most common endocrinopathy in aged horses.¹ Yet Australian studies suggest it remains significantly under recognised by owners.² With a prevalence of 21.2% in horses over 15 years,³ PPID poses a clinical challenge that requires staying up to date with current diagnostic and management strategies, alongside careful assessment for insulin dysregulation (ID) and equine metabolic syndrome (EMS).⁴
PPID primarily affects horses over 12 years of age, with some studies showing the mean age of affected animals as >20 years.3,5 While owners often dismiss early clinical signs as normal aging,² veterinarians should remain vigilant for suggestive clinical signs, including:
• Laminitis, divergent growth rings, atrophy of epaxial muscles
• Delayed healing, abnormal sweating, polyuria, polydipsia
• Exercise intolerance, infertility
Only hypertrichosis is pathognomonic for PPID.6,7 As a neurodegenerative disease, early intervention improves outcomes.⁷
Diagnosis & management
The updated 2024 recommendations by the Australian and New Zealand (ANZ) Equine Endocrine Group, supported by Boehringer Ingelheim, provide guidance based on recent research specific to ANZ horse populations.4
Basal ACTH testing remains the most practical diagnostic method,⁷ though proper sample handling is critical. Blood must be collected in EDTA tubes, chilled within three hours, and processed within 12 hours to avoid erroneous results.⁷ Seasonal variation significantly impacts ACTH concentrations, with higher levels expected during autumn (February-May),⁸ requiring careful interpretation alongside clinical signs.
Recent research highlights breed-specific considerations, with healthy Arabians, some pony breeds, and donkeys showing higher ACTH concentrations, particularly in autumn.⁹,¹⁰ For challenging cases, TRH stimulation testing offers enhanced diagnostic sensitivity.⁷
Pergolide mesylate remains the gold standard treatment for PPID, with Prascend® 1mg Tablets for Horses being a recommended therapeutic option indicated for the control of clinical signs associated with PPID. This synthetic ergot derivative acts as a potent, long-acting dopamine receptor agonist, inhibiting ACTH and α-MSH production and release from pituitary gland’s intermediate lobe. Lifelong treatment is anticipated, as clinical signs return if treatment ceases.¹¹
Critical to successful management is recognising the concurrent presence of ID.⁷ While not all horses with PPID develop laminitis, it is considered the most severece. Although the link between PPID and laminitis is not completely understood, evidence suggests association with ID.12 Laminitis predisposition is common to both EMS and PPID,13 with hyperinsulinaemia potentially more marked when these diseases occur concurrently.7 This presumably leads to an increased risk of laminitis7 thus necessitating ID assessment using oral sugar or in-feed oral glucose tests rather than basal insulin measurements alone.¹⁴
PPID management extends beyond pharmacotherapy, with preventative healthcare playing a vital role. This includes:
• Targeted parasite control (PPID horses show increased egg shedding)¹⁵
• Routine dental and hoof care⁷
When ID is concurrent, essential management includes:
• Dietary modification: <10% non-structural carbohydrates¹⁶
• Pasture restriction and hay soaking¹⁷
• Tailored exercise programs based on physical condition 16,18
Given PPID’s progressive nature, ongoing monitoring is essential. ACTH testing is recommended every 6-12 months,⁷ ideally in the same season each year to ensure an accurate trend assessment.4 Clinical signs and insulin status remain the most important indicators for treatment success. 4
Download the updated Recommendations for the Diagnosis and Management of PPID, ID and EMS on Boehringer Ingelheim’s Animal Health Academy. For all references mentioned in this article, please refer to page 20 of this document. Access code for new users: myAcademy
