Cushing’s Syndrome in Horses

Alex German
Feb 05, 2010
3 min read
Image: Photo Grapher / via Image Bank

Could Your Shaggy, Thirsty Horse be Suffering from Cushing’s Disease?

Equine Cushing’s disease occurs when a tumor called a pituitary adenoma develops in the pituitary gland. As this tumor slowly grows, it sends inappropriate signals to the rest of the body to secrete excessive hormones — primarily a stress hormone called cortisol. Too much cortisol can affect the body negatively in many different ways. This disease in horses is similar to Cushing's disease in humans and in dogs.

Cushing's disease is predominantly diagnosed in horses over seven years of age. Although there is no clear breed predilection for the disease, ponies appear to be more prone to Cushing’s disease than horses.

Signs and Types

Signs of Cushing’s disease are usually slow to develop, but are progressive.

  • Laminitis (inflammation within the structure of the hoof)
  • Weight loss
  • Ulcers in mouth
  • Excessive thirst (i.e.,frequent trips to the water trough, water hole, etc.)
  • Excessive Urination (due to excessive drinking)
  • Hirsutism (long, thick coat) and abnormal shedding
  • Changes in body shape (e.g., development of large fat deposits along the mane, muscle wasting, and pot-belly)
  • Prone to infection (which may cause cuts and scrapes to take longer to heal)

Causes

The cause of Cushing's disease in horses is a tumor found in the pituitary gland. This tumor affects the pars intermedia - the small middle region of the pituitary gland. Sometimes equine Cushing's disease is also referred to as pars intermedia dysfunction (PID).

Diagnosis

While the above symptoms may indicate that a horse or pony is suffering from Cushing’s disease, there are other issues that could be to blame. A veterinarian must first complete a physical exam, along with a complete blood profile to rule out other causes. Once that is done, there are special blood tests that can be run to properly diagnose this condition and form an effective management scheme for the disease.

Treatment

Although there is no definitive treatment for equine Cushing's disease, there are a handful of ways to manage and effectively control it. Pergolide is the medication of choice; anywhere from 0.2 to 5 milligrams orally per day has been shown to stabilize the health of most horses. If effective, the veterinarian may then gradually reduce the dosage.

Outside of pergolide, bromocriptine is another drug that has been used for managing Cushing’s disease in horses, though it is less popular than pergolide. Cyproheptadine is another drug that has been utilized for treating this condition as well. Before pergolide, cyproheptadine was the drug of choice for Cushing's, and in some cases a combination of cyproheptadine and pergolide is used to manage the condition.

Living and Management

After diagnosis and starting medication for Cushing’s disease, there are other management practices one can implement to help a horse with this condition. Horses with Cushing's disease are extremely prone to laminitis, a debilitating inflammatory condition inside the hoof. Regular farrier visits and limited access to lush pasture will help prevent this. Careful management of the horse's diet will help combat weight loss. Lastly, because Cushing's disease weakens the horse's immune system, make sure to properly clean and disinfect any superficial wounds found on the horse's body.

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