Pituitary Pars Intermedia Dysfunction (PPID, formerly Cushing's disease) is extremely common in older horses and significantly impacts welfare if undiagnosed and untreated.
PPID welfare represents a chronic, progressive condition whose welfare impact depends entirely on diagnosis timing. Horses in the early stages of PPID that receive pergolide treatment maintain good quality of life for years. Horses with undiagnosed PPID progress through increasing muscle wasting, immune suppression, and eventually laminitis - each stage representing increasing suffering that treatment could have prevented. Hirsutism (the abnormal woolly coat) is one of the most visible signs but develops relatively late in the disease process, meaning earlier signs including subtle behavioral changes and seasonal ACTH testing are more valuable for early diagnosis.