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Cushing's Disease in Horses

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Lindsay Butzer, DVM
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Dr. Lindsay Butzer
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Beautiful Brown horse in pasture

Cushing's Disease, also known as pituitary pars intermedia dysfunction (PPID), happens to horses when their body overproduces certain hormones, including cortisol.

The excess production of hormones affects the whole body, causing a wide range of changes in your horse's physical appearance, behavior and overall health.

This condition is incredibly common, occurring in around 20% of horses over fifteen years of age. While it's not curable, the symptoms can be managed with medication, dietary changes and treatment, giving your horse many more relatively healthy, happy years.

What Are The Symptoms of Cushing's Disease In Horses?

The classic symptom of Cushing's in horses is a long, curly coat that does not shed in the spring.

You may also notice other physical changes like weight loss, muscle wasting along the topline, a potbelly and fatty deposits around the eyes, tail, sheath (in males) and neck.

The condition is sometimes associated with insulin resistance. That means your horse's body may no longer utilize sugar properly, resulting in an increase in blood sugar. This can lead to a predisposition to laminitis, and can also cause diabetes if dietary changes are not made.

Not all horses with Cushing's will have insulin resistance. Ask your veterinarian to test your horse's insulin and blood sugar levels, and only make dietary changes under their guidance.

Cushing's can also diminish your horse's immune system, so your horse may become more prone to infection. Skin infections and gingivitis can be more prevalent in horses with Cushing's.

Your horse may drink more water, and urinate more frequently. It's also common for horses with Cushing's to experience increased sweating.

Lethargy is also a common symptom. Your horse may not perform athletically as well as they once did. However, your horse's appetite may increase, so you might have to adjust their diet to keep them from putting on excess weight.

In mares, you may notice irregular or ceased estrus cycles. Infertility can also occur, as well as prolonged lactation after their foal has been weaned, or even lactation with no foal at all.

Left untreated, severe, debilitating symptoms such as seizures, weakness and blindness can develop.

How Is Cushing's Disease In Horses Treated?

If your horse has some of the above symptoms, you'll need to see your veterinarian for a diagnosis. Some symptoms are similar to those of other chronic conditions, so you'll need to make sure your horse does, indeed, have Cushing's before moving forward with treatments and dietary changes.

Diagnosing Cushing's only requires a simple blood test to check for elevated hormone levels.

Once your vet diagnoses your horse, they may prescribe Prascend, which greatly reduces the symptoms associated with Cushing's disease by stimulating your horse's brain to produce more dopamine, which in turn controls the excess production of hormones. Once diagnosed, your horse will need to be on medication for the rest of their life.

If your horse is experiencing insulin resistance as a result of Cushing's, you will need to limit their starch and sugar intake. Soaking your horse's hay before feeding can reduce starch and sugars. You can also try adding HEIRO Insulin Resistance supplement to your horse's feed, which helps treat elevated insulin.

Managing your horse's diet can help protect them against other related health issues. Feeding plenty of high-quality protein can help reduce muscle loss. Your vet can help you create a custom dietary plan that is tailored to your horse's needs.

You'll also need to treat secondary health conditions as they arise. You should see your vet twice per year to keep your horse's health in check.

Horses with Cushing's become more susceptible to parasites. Your horse may need regular fecal-egg counts and more frequent deworming as a result.

You may need to clip your horse's coat if their inability to shed properly is causing them to overheat. Also, visit your farrier more frequently to prevent laminitis, and treat it early if it develops.

Around 6-12 weeks of taking Prascend, most horses show significant improvement. Though you will need to continue to monitor for secondary conditions, your horse can enjoy a good quality life for years after their diagnosis.

To help with pain and inflammation, you can start giving your horse an omega-3 fatty acid supplement. Supplements that provide amino acids like lysine, methionine, and threonine can help with muscle loss. Also ask your veterinarian about adaptogenic herbal supplements like Rhodiola rosea, which may help regulate cortisol in horses with Cushing's Disease. Chasteberry extract is another popular herbal treatment, but research studies have shown mixed results in proving whether or not it is effective.

Holistic and conventional treatments can be combined to give your horse the best chance of improving and having a good quality of life for years after diagnosis. Always keep your veterinarian up to date on what herbs, holistic treatments and dietary changes you may be using to help your horse, as some can counteract with certain medications.

Why Do Horses Get Cushing's Disease?

Cushing's disease is very common in older horses, and there does not seem to be a genetic cause. It's also not contagious. It's caused by degeneration of the nerves that control the pituitary gland, likely brought on by oxidative stress that naturally occurs from exposure to sunlight, pesticides, infections, physical activity, and many normal, day-to-day things from which you cannot always protect your horse.

Antioxidants can help protect your horse against oxidative stress. Vitamins A, C, and E, as well as selenium, are all antioxidants that can help. They can come from food or supplements.

Besides feeding a high-quality diet rich in antioxidants, there is not much you can do to prevent Cushing's disease. It happens to horses of either sex, of any breed, and though it's most commonly diagnosed in horses over 15, it can develop in horses that are much younger.

The best thing you can do is to be on the lookout for symptoms, and see your veterinarian for regular checkups. Catching Cushing's Disease early can delay the onset of symptoms and prevent associated health issues.

In recent years, we have learned more about equine Cushing's disease, and discovered that it no longer means the end of your horse's riding career. By managing symptoms, you can ensure your horse will still have an excellent quality of life for many years to come.