Cushings Disease in Horses Explained

Cushings disease in horses is a disorder of the pituitary gland. The middle lobe of the pituitary gland becomes enlarged, and in doing so, over-produces hormones. At the same time, it pushes on nearby glands causing them to under-produce hormones.

Cushings disease causes long hair growth in horsesCushings disease in a 25 year old mare

One result can be an over production of insulin and the inability for the animal’s body to properly absorb blood sugar. It is called insulin resistance.

Although equine cushings disease can affect younger horses, it usually found in horses over the age of 15. Any breed of horse can develop cushings but it is most commonly seen in ponies and Morgans.

Symptoms of Cushings Disease

  • Excessive drinking
  • Excessive urination
  • Excessive sweating
  • Decreased immunity to infection
  • Loss of muscle
  • Infertility
  • Bulging eyes
  • Long curly coat that refuses to shed (hirsuitism)
  • Prone to laminitis
  • Insulin resistance

Some of the symptoms of cushings disease in horses are very similar to equine metabolic syndrome (EMS). They both have insulin resistance and are at extremely high risk of laminitis. Because of the similarities, EMS has been called ‘peripheral cushings disease’.

Diagnosing Cushings Disease in Horses

There are several different blood tests available to help diagnose for equine cushings disease. These tests are not 100% accurate, as they have been known to give false positives during certain times of the year. Early diagnosis relies on blood tests, while later diagnosis of cushings disease is confirmed with a combination of a blood test and the presence of hirsuitism (long curly hair). Keep in mind that hirsuitism does not show itself in the early stages of cushings disease.


Currently there is no cure for cushings in horses. It is believed that horses with cushings suffer from low levels of the hormone dopamine. The drug Pergolide is used to help control the production of dopamine. Because too much Pergolide can have very ill side effects it is important to give the smallest dose necessary to get the job done. This may require several blood tests to get the dose just right. The horse will then be on the drug for the rest of their life.

Loss of muscle with cushingsLoss of muscle with cushings

The symptoms of cushings can be treated to make the animal more comfortable; starting with a specialized diet, if the horse has insulin resistance. Not every horse with cushings will have insulin resistance, but it is very common.

If so, it is important that the horse be feed a low sugar, low carbohydrate, low starch diet with limited access to green pasture. Your veterinarian is the best resource for developing a proper diet for a horse diagnosed with insulin resistance.

The sooner cushings disease in horses is diagnosed, the better chance the animal has to avoid crippling laminitis. Healthy weight control, exercise, regular dental and regular hoof care may play a factor in the prevention of cushings disease in horses.

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This information is written for the horseman to better understand and cope with the variety of disease and injury that can occur during the course of horse ownership. Always consult with your Veterinarian regarding the care and treatment of your equine.

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