Long-Term Response of Equids With Pituitary Pars Intermedia Dysfunction to Treatment With Pergolide.
Authors: Schott Harold C, Strachota Julie R, Marteniuk Judith V, Refsal Kent R
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Long-Term Pergolide Response in Equine PPID Pituitary pars intermedia dysfunction (PPID) remains one of the most common endocrine disorders in geriatric horses, yet longitudinal data on treatment efficacy beyond a few years are scarce; this 14-year prospective study followed 30 client-owned equids (28 horses, 2 ponies) receiving either 2 or 4 μg/kg pergolide daily to document sustained clinical and biochemical responses. Owners were interviewed quarterly and equids underwent clinical re-evaluation at multiple timepoints, with endocrine testing performed throughout the extended follow-up period. Clinical improvement was maintained in nearly all animals throughout the study despite a median survival time of only 3.6 years; notably, whilst seven of the 13 animals initially receiving the lower dose required escalation to 4 μg/kg between 1.7 and 4.7 years of treatment, the majority did not need dose adjustments, challenging the assumption that progressive dose increases are inevitable with chronic PPID management. Endocrine test results normalised in 75% of the 13 surviving equids at 5.5 years, though this declined to just two of six by 9.5 years—suggesting that whilst clinical signs respond well to pergolide, biochemical control may become more difficult to achieve in the longer term. These findings provide reassuring evidence that pergolide delivers sustained clinical benefit for most PPID-affected equids and that individualised dosing strategies, rather than routine dose escalation, may be appropriate for animals showing good initial response.
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Practical Takeaways
- •Pergolide provides sustained clinical improvement in most PPID cases, but owners should expect variable endocrine normalization and not assume test results will remain normal long-term.
- •Initial dosing strategy can be effective long-term in many horses without automatic escalation; monitor clinical response rather than routinely increasing dose.
- •PPID-affected horses remain at significant risk for chronic laminitis complications requiring euthanasia, necessitating comprehensive management beyond pergolide alone.
Key Findings
- •Long-term pergolide treatment produced clinical improvement in nearly all PPID-affected equids over the 14-year study period.
- •Endocrine test results normalized in 75% of surviving equids after 5.5 years but declined to normal in only 2 of 6 (33%) after 9.5 years of treatment.
- •Seven of 13 equids initially receiving 2 µg/kg required dose escalation to 4 µg/kg between 1.7–4.7 years, while others maintained response at initial dosage.
- •Median survival time was 3.6 years (range 0.6–10.5 years); five equids died and 24 were euthanized, with five euthanized specifically for chronic laminitis.