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.

Different horses show different symptoms of Equine Cushings Disease. The most common symptom is coat changes (longer, thicker, curly, failure to shed in Spring, becoming lighter in color). The heavier coat results in increased sweating as a secondary symptom, due to over-heating, especially in summer. The horse tends to lose muscle in its neck and back, despite increased appetite and eating more, while developing a pendulous abdomen. Diabetes often develops, with an associated increase in water consumption and urination. Laminitis always develops eventually. The horse becomes more prone to infections and slower to heal from external injuries due to a depressed immune system. The natural depressions above the eyes tend to fill in with fat.

Studies have determined that many older ponies (and to a lesser extent horses) have ECD but have not been diagnosed, with the result that they were not receiving controlling treatment in the early stages of the disease (the point at which treatment is most beneficial). Increased care is needed with older equines to identify ECD promptly. Although this can be done by careful observation of potential symptoms, blood and urine tests are often used to confirm that the cause is ECD and not some other disease.

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).

Since ECD and produce other illnesses, such as diabetes and laminitis, one needs to watch for symptoms of these related problems and treat promptly before they become serious.

One should also maintain the horse’s quality of life by treating any symptoms which make it uncomfortable. For example, if the heavier coat results in the horse becoming too warm, one should clip the coat in spring or summer.

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