Prevalence, risk factors and clinical signs predictive for equine pituitary pars intermedia dysfunction in aged horses.
Authors: McGowan T W, Pinchbeck G P, McGowan C M
Journal: Equine veterinary journal
Summary
# Editorial Summary: PPID Prevalence and Clinical Recognition in Aged Horses Equine pituitary pars intermedia dysfunction (PPID) represents a progressive neurodegenerative condition in older horses, yet remains substantially under-diagnosed in practice despite affecting over one in five horses aged 15 years or older. McGowan and colleagues conducted a large-scale survey in Queensland combining owner questionnaires with veterinary examinations and seasonal-adjusted basal ACTH testing to establish prevalence figures and identify reliable diagnostic predictors; remarkably, they found PPID present in 21.2% of aged horses, though most owners were unaware their animals had the condition. Whilst numerous clinical signs showed univariable associations, only advancing age (odds ratio 1.18 per year; P<0.001) and owner-reported hirsutism—particularly delayed coat shedding or abnormally long hair—emerged as reliable multivariable predictors (OR 7.80; P<0.001), with routine haematology and biochemistry offering no diagnostic support. The findings underscore the critical importance of recognising hirsutism as a sentinel clinical sign warranting ACTH testing in aged horses, rather than dismissing it as cosmetic or breed-related, since early detection enables timely intervention before more advanced clinical dysfunction develops. For practitioners managing geriatric populations, this work reinforces that seasonal adjustment of basal ACTH reference ranges is essential for accurate diagnosis, and that proactive screening of horses with delayed shedding—even when owners have not formally reported a diagnosis—represents a significant opportunity to improve welfare outcomes in this age group.
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Practical Takeaways
- •Screen horses aged 15+ years for PPID even when owners haven't recognized clinical signs; 1 in 5 aged horses may be affected
- •Prioritize testing horses showing delayed coat shedding or hirsutism as these signs are strongly associated with PPID diagnosis
- •Don't rely on routine blood work alone to diagnose or rule out PPID; use seasonally adjusted basal ACTH testing instead
Key Findings
- •PPID prevalence in horses aged ≥15 years is 21.2%, despite being under-recognized by owners
- •Age and owner-reported hirsutism are the only significant risk factors retained in multivariable analysis (OR 1.18 per year and OR 7.80 respectively)
- •Routine haematological and biochemical variables do not support diagnosis of PPID
- •Seasonally adjusted basal ACTH concentrations are more reliable than α-MSH for PPID diagnosis in aged horses