Equine Cushings Disease – Symptoms and Treatment
Cushing’s disease occurs in various animals (e.g. dogs, horses, people), although the symptoms in horses are different than the symptoms in other animals (e.g. in dogs it results in hair loss whereas in horses it results in greater hair growth). When the disease occurs in horses, it is known as Equine Cushings Disease (or ECD).
ECD is an illness caused by excessive hormone production. The pituitary gland produces too much hormone, which over-stimulates the adrenal glands, which in turn produce too much steroids. It is the excessive quantity of steroids which causes the symptoms associated with ECD. The over-production of the pituitary can be caused various changes, such as the growth of benign tumors, enlargement of the pituitary due to age-related changes, or a decline in the regulatory chemical dopamine due to age-related changes in the brain. All of these factors tend to be age related, so the disease is much more common in older horses (over 15 years) although it has been found in horses as young as seven years.
Cushings was first identified in explained in’21, by Dr. Cushing, after whom the disease is name. ECD is the equine variation of the disease first identified in humans by Dr. Cushing.
The most common symptom of ECD is coat changes (becoming curly, thicker, longer, failure to shed, lighter in color). Sweating tends to increase as a result of the heavier coat. There is muscle loss in the back and neck, even when the horse increases its food intake. Laminitis eventually develops. Diabetes usually develops, with the result that the horse drinks and urinates more than normal. Due to the immune system being depressed, the horse is more prone to infections and slower to heal from injuries. The depressions over the eyes tend to disappear due to fat deposits.
Any of these symptoms can be caused by a variety of illnesses other than ECD. Consequently, blood and urine tests are normally used to confirm that the cause is ECD (e.g. by measuring hormone levels and hormone response levels) and to rule out other possible diseases. Studies have shown that many horses with ECD are either not diagnosed or incorrectly diagnosed (the symptoms are incorrectly attributed to a different disease), with the result that they do not receive appropriate treatment.
Unfortunately it is not possible to cure ECD. However, one can slow the disease by the use of medication to reduce hormone production to normal levels. Note that some of these medications have strong side effects, so appropriate testing and control is required to prevent secondary illnesses (e.g. liver disease).
As cushings disease can result in the development of secondary diseases (e.g. laminitis, diabetes), the horse needs to be closely monitored for any symptoms of these, with appropriate and prompt treatment.
Finally, one should make the horse more comfortable by treating the individual symptoms. If the horse is over-heating due to a heavier coat, one should clip the coat to make the horse more comfortable.
Dr. Douglas Stewart is the author of Cushings Disease in Horses and owner of Horses for Sale
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