Cushing’s Syndrome in Horses

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)


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).


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.

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