PPID, formerly called equine Cushing disease, causes progressive hormonal dysregulation in older horses and responds well to treatment that significantly improves welfare.
PPID causes significant progressive welfare harm through multiple mechanisms. The failure to shed the winter coat causes thermal discomfort and skin problems. Muscle wasting reduces body condition and physical capacity. Laminitis in PPID horses causes chronic severe foot pain. Increased infection susceptibility from immune dysregulation causes repeated illness. Pergolide treatment effectively improves most clinical signs and dramatically reduces welfare burden in responding horses. Early diagnosis before severe clinical signs develop is important for welfare: ACTH screening in older horses from 15 years onwards enables treatment to begin before significant harm has accumulated.