Pituitary pars intermedia dysfunction (PPID), known as equine Cushing's disease, is the most common endocrine disorder of older horses, causing progressive welfare compromise without treatment.
Untreated PPID causes progressive welfare decline through multiple pathways: muscle wasting reduces mobility and comfort; chronic infections from immunosuppression cause recurring illness; and laminitis causes severe, often debilitating foot pain. The condition is easily overlooked in early stages when the characteristic long curly coat is the only sign. Early diagnosis and pergolide treatment significantly slows progression and prevents laminitis development. Welfare monitoring should include twice-yearly ACTH testing to ensure dose adequacy, dietary management (low non-structural carbohydrate diet to reduce laminitis risk), and regular dental care (PPID causes dental problems including EOTRH - equine odontoclastic tooth resorption and hypercementosis). The PPID-associated quality of life for horses receiving appropriate treatment is often excellent for years.