This article originally appeared in the Fall 2026 issue of EquiManagement. Sign up herefor a FREE subscription to EquiManagement’s quarterly digital or print magazine and any special issues.One research group found that 88% of pergolide-treated horses had a decreased response to TRH after 100 days of treatment. | Bianca McCarty
Pituitary pars intermedia dysfunction (PPID) remains one of the most commonly diagnosed endocrine disorders in aging horses, yet questions about prognosis, disease progression, and treatment response continue to evolve. Recent research is providing insights into how PPID affects long-term health and life expectancy, while also helping veterinarians better understand how pergolide influences diagnostic testing and disease control.
Life Expectancy and Health Risks in PPID Horses
About 20% of horses older than 15 develop PPID, which can lead to a number of secondary problems. Nearly 77% of horses with PPID also develop insulin dysregulation (ID).
In a retrospective study, researchers at Purdue’s College of Veterinary Medicine reviewed medical records from 1996-2024 of 132 horses diagnosed with PPID. The diagnosis was based on elevated adrenocorticotropic hormone (ACTH) levels at rest or challenged with thyrotropin-releasing hormone (TRH) stimulation testing and on clinical signs and/or necropsy results. The researchers matched these records by age and breed with 274 controls.
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