The Life Span of Horses With Cushing's Disease

Cause

• ECD is caused by a malfunction of the pituitary gland, which is located at the base of the brain. This causes increased stimulation of the adrenal glands, which lie under the backbone just in front of the kidneys. The adrenal glands produce the body's steroids, and overactive adrenals produce marked hormonal imbalances in the horse and account for the clinical signs. The overactive pituitary gland can develop hypertrophy, or enlargement due to excessive work, causing a development of benign tumor cells, which puts pressure on the brain.

Symptoms

• The most common sign of ECD is hirsutism--growth of a shaggy, long hair coat that does not shed in the spring and lasts through the summer. An increased intake of water with a parallel increase in the amount of urine passed is also one of the first signs. Profuse sweating on the shoulders and neck are common. Loss of muscle tissue in the rump and along the back is often found. However, at first glance this may go unnoticed since ECD horses have increased fat deposits over the tail head and a thick pad of fat along the top of the neck. A thorough examination by a veterinarian is needed to determine the muscle loss. Due to excessive corticosteroid production and changes in the blood flow of the hooves, most ECD horses develop laminitis--metabolic and vascular disease of the inner sensitive structures of the feet--and chronic foot abscesses.

Diagnosis

• The diagnosis of ECD is based on hirsute, muscle loss and a dexamethasone suppression test (DST). A blood sample is taken from the horse and tested for corticol level. After the initial blood sample is drawn, a specific dose of the corticosteroid dexamethasone is given to the horse. Twenty-four hours later, a second blood cortical level is sampled. If the second blood cortical stays markedly above the first sample's level, the diagnosis of equine Cushing's disease is definitive.

Treatment

• Once the horse has been diagnosed with ECD, drug therapy is available using cyproheptadine, hypochloride, bromocriptine, or pergolide prescribed by a veterinarian. Medication must be given daily, which is quite costly. Additionally, routine blood work performed by the veterinarian is essential. If treatment is stopped, the horse will quickly show sings of EDC within a few weeks. Horses with hirsutism are much more comfortable during the summer if their coat is shaved.

Prognosis

• Veterinarians have found pergolide to very effective, adding years to the geriatric horse's life. Pergolide stimulates dopamine release, which tells the pituitary gland to shut down. Research has shown that this drug is very effective with minimal side effects. Another drug, trilostane is being tested. This drug actually works on the adrenal gland, slowing down the production of cortisol. Symptoms of ECD have actually been reversed when treating with Trilostane.

  Proper diet is crucial to managing a horse's condition with Cushing's Disease. Providing a diet high in antioxidants, such as vitamins E and C, may aid in treatment of horses with ECD. Their feed should also consist of a low-sugar, low-starch mixture. Typically, this means eliminating alfalfa hay and grain. Instead, they should consume grass hay, along with pelleted feed only if they are having difficulty maintaining proper weight.

  When this disease is diagnosed early on, proper treatment can reduce the symptoms and allow the horse to lead virtually a normal life. Even in horses that are at a progressed state of ECD, proper treatment has positive effects on longevity and quality of life.