Cushing’s disease occurs in horses when the pituitary gland in their brain becomes overactive. The gland produces excessive amounts of hormone which, in turn, leads to excessive production of steroids by the adrenal glands which it controls.
There is currently no known reason why any given horse may develop this condition also some consider that it is a natural result, in some ponies, of old age.
The average age of horses affected by this condition is 20 years. The clinical signs of the disease are related to the over production of the adrenal gland hormones. This excessive production of steroids causes the horse to drink excessively and produce large amounts of urine which is called polydipsia and polyuria respectively. The horse may also become lethargic and unwilling to exercise.
Another quite striking sign of disease is that some animals stop naturally shedding their coats and become excessively hairy, known as hirsutism. As the hormones that are produced inhibit the horse’s immune system, affected animals become more prone to developing other diseases such as liver disease and pneumonia. Horses affected chronically are also much more prone to developing laminitis and do not respond to normal treatment.
There is no known inciting cause of Cushing’s and therefore it is impossible to actively prevent this condition from developing. However, early diagnosis and treatment can ensure that the horse lives a relatively normal life for many years after the initial diagnosis. It is important therefore that if you suspect your horse may have Cushing’s disease you contact your vet to discuss any concerns with them.