Cushing's Disease in Horses

Equine Cushing's Disease results from the increased production of cortisol and other hormones. This is caused by a pituitary gland abnormality and is mainly seen in older horses and ponies. The disease is assessed through a series of blood tests. The horse's condition can then be improved through medication and proper maintenance.

Cushing's disease, or hyperadrenocorticism, is caused by a tumor in the pituitary gland. Though the tumor is usually benign, its presence causes a series of effects. This disease usually develops in horses around the age of 20 or older, even though it has occurred in younger horses.

Cushing's disease is also connected to abnormal activity of the HSD enzyme in the cells. HSD is 11-beta hydroxysteroid dehydrogenase, which works to maintain normal levels of cortisol in the cells. When the amount of HSD is increased in the cells, this causes an increase in cellular cortisol levels above the normal limits. The signs of Cushing's disease are then exhibited.

The most common symptoms of Cushing's syndrome are: - Extreme thirst or polydipsia, coupled with excess urination, or polyuria; - Growth of heavy, curly and coarse hair that does not shed; - Sweating and seborrhea; - Pot belly and swayback stance; - Increased appetite; - Heavy eyelids; - Chronic laminitis; - Some muscle loss; - Compromised immunity; - Overall sick appearance; - Dull coat.

Tests are performed to confirm the presence of Cushing's disease. The dexamethasone suppression test (DST) is used to assess the affect of dexamethasone on the Adrenocorticotropic hormone (ACTH) production. It normally blocks its secretion, but in Cushing's syndrome, the dexamethasone will not be able to stop the ACTH production. Insulin levels are also assessed as a test for Cushing's disease. Insulin levels are increased in Cushing's disease from the effects of high cortisol levels.

After repeated blood tests, treatments are prescribed to restore the horse's health. If the disease is caught early, treatment can be very successful. There are several medications that are effective in treating Cushing's disease. There are herbal treatments, as well. These, however, do not address the pituitary tumor, which can continue to grow and compromise the horse's health. Some common medications for Cushing's disease include cyproheptadine, pergolide mesylate, and bromocriptine mesylate. A promising herbal treatment for the early stages of Cushing's disease is the chaste berry (Vitex agnus castus).

While Cushing's disease is not curable by treatments that are currently available, the horses can be treated to improve their quality of life. Preventive measures can also be taken to prevent the appearance of the disease in horses that do not have Cushing's disease. Owners and caretakers can reduce the stress on the animals. Make the horse's environment comfortable and safe. Feed the animal on a consistent schedule and do not introduce too much change in the horse's daily routine. Shave the horse's thick coat when it's warm, and groom the horse to prevent disease. Take care of the horse's hooves and teeth. Deworm and immunize your horse, and provide adequate nutrition, and avoid placing the horse with unfamiliar or aggressive horses. These measures will greatly improve the quality of life of a horse with Cushing's disease.