Equine Cushing's Disease (PPID): Managing Aged Horses
Cushing's disease in horses causes coat changes, laminitis, and immune suppression. Early detection and management keep horses comfortable.
Pituitary pars intermedia dysfunction (PPID), commonly called Cushing's disease, is an endocrine disorder of aged horses. A benign tumor of the pituitary gland overproduces hormones, causing metabolic disturbances, laminitis, and immune dysfunction. It's one of the most common conditions in horses over 15 years.
Key Points
- PPID affects approximately 20% of horses over 15 years
- The classic sign is a long, curly coat that doesn't shed (hirsutism)
- Laminitis is the most dangerous complication
- Diagnosis is confirmed by ACTH stimulation test or TRH stimulation test
- Pergolide (Prascend) is the treatment of choice
- Regular monitoring and dose adjustment are needed lifelong
Understanding PPID
The pituitary gland normally produces hormones that regulate body functions. In PPID, the pars intermedia (middle lobe) enlarges and overproduces ACTH, melanocyte-stimulating hormone, and other peptides. This causes excessive cortisol production and metabolic disruption. The disease progresses slowly over years. Some horses show signs in their teens; others not until their twenties. The exact trigger is unknown but involves oxidative damage to dopaminergic neurons.
Clinical Signs
Hirsutism — a long, curly, non-shedding coat — is the most recognizable sign. Chronic laminitis that doesn't respond to usual treatment is common. Excessive thirst and urination (PU/PD) develop. Muscle wasting along the topline creates a pot-bellied appearance. Recurrent infections — sinusitis, skin infections, hoof abscesses — reflect immune suppression. Lethargy and decreased performance occur. Some horses show abnormal fat deposits above the eyes. Delayed wound healing is common.
Treatment with Pergolide
Pergolide mesylate (Prascend) is a dopamine agonist that suppresses pars intermedia hormone production. Starting dose is 1 mg orally once daily. Improvement is seen within 1-3 months — coat shedding begins, laminitis stabilizes, and energy improves. Some horses need 2-3 mg daily. Side effects include loss of appetite and mild depression, usually transient. Compounded pergolide is less stable and not recommended. Regular ACTH monitoring every 6-12 months guides dose adjustment.
When to See a Vet Immediately
- Your horse has a long, curly coat that doesn't shed normally
- There's chronic or recurrent laminitis
- Excessive drinking and urination are present
- Recurrent infections occur despite good care
- Your horse is over 15 years with declining condition
How RVC Can Help
This article is for educational purposes only and does not replace professional veterinary advice. If your pet is showing any symptoms, please contact Royal Veterinary Center immediately at +853 6677 6611.