Equine Pituitary Pars Intermedia Dysfunction (Cushing's Disease) in Horses

Equine Pituitary Pars Intermedia Dysfunction (PPID), commonly called equine Cushing's disease, is the most common endocrine disorder in older horses and ponies, causing significant welfare compromise if unmanaged.

Key Facts

PPID affects an estimated 15-30% of horses over 15 years of age, making it extremely common in the geriatric equine population
The condition is caused by dysfunction of the pituitary gland's pars intermedia, leading to excess ACTH production
The most recognisable sign is hypertrichosis — an abnormally long, curly coat that fails to shed seasonally
PPID predisposes horses to laminitis, a severely painful foot condition that is a leading cause of euthanasia in affected animals
Other signs include muscle wasting over the topline, increased drinking and urination, and increased susceptibility to infection
Pergolide mesylate (Prascend) is an effective daily oral medication that controls PPID in most horses
Regular dental care is especially important in PPID horses as the condition accelerates dental disease

Welfare Considerations

PPID causes insidious welfare compromise that often progresses significantly before owners recognise the disease. The hypertrichotic coat — while visually dramatic — is less welfare-significant than the metabolic consequences: secondary laminitis is acutely and chronically painful, causing horses to shift weight constantly, lie down more than normal, and show obvious distress when forced to move. Muscle wasting over the hindquarters and topline progressively impairs comfort and function. Increased infection susceptibility means that minor wounds and respiratory infections become more serious. The welfare impact of well-managed PPID is dramatically reduced: pergolide treatment normalises ACTH, reduces laminitis risk, improves coat shedding, and restores muscle condition. Annual ACTH testing of horses over 15 — particularly in autumn when ACTH is physiologically elevated — enables early detection before significant welfare harm has occurred.

What You Can Do

Have horses over 15 years tested annually for PPID using resting or thyrotropin-releasing hormone-stimulated ACTH
If your horse is diagnosed with PPID, start pergolide promptly and commit to lifelong daily medication
Manage diet carefully in PPID horses — low-sugar, low-starch forage reduces laminitis risk
Monitor coat shedding and body condition regularly as indicators of treatment response
Seek farriery support to manage hoof care and reduce laminitis risk in affected horses