May 27

Written by: Surgi-Care Center for Horses
5/27/2011 4:16 PM 

Cushing’s disease in horses is a disease that comes with age. It is caused by a benign tumor affecting a part of the brain known as the pituitary gland. The exact reason for the formation of the tumor is unknown. The tumor, a pituitary adenoma, interferes with the body’s normal hormonal balance due to the space it occupies in the brain as well as an overproduction of hormones and peptides.

Advances in veterinary medicine, nutrition, and farriery have allowed horse owners to enjoy their horses for much longer than in the past. The increase in the geriatric population of horses is paralleled with an increase in the number of horses showing clinical signs of Cushing’s disease. The average age of horses diagnosed with Cushing’s is 21 years old, with a range from 12 to 35 years of age. It has been reported in horses as young as 7 years old.

The most common clinical signs of Cushing’s is an excessively long hair coat, which often fails to shed out in the warmer months. Other clinical signs include: weight loss, lethargy or poor performance, laminitis, increased water intake and urination, increased sweating, and mares may fail to cycle. The onset of these clinical signs is usually gradual over a year or more, but can also develop rapidly.

The tumor’s location interferes with normal hormone secretion, which in turn leads to changes manifested through the clinical signs as well as secondary complications. The major complications of Cushing’s includes diabetes mellitus and a decreased immunity, which predisposes horses to secondary infections. Veterinarians can diagnose Cushing’s disease through laboratory blood work and with special tests (ACTH stimulation and dexamethasone suppression tests) that evaluate the levels of hormones affected by the tumor.

There is no cure for Cushing’s disease, but the good news is that there are medications available which usually improve the clinical signs. Improvement of clinical signs will most often improve the quality and length of life for your horse. Some of the medications used to treat horses with Cushing’s include pergolide, bromocriptine and cyproheptadine. Studies have shown that pergolide is the most effective drug to control Cushing’s disease. These drugs help to balance your horse’s hormones by reducing the secretion of cortisol and other hormones responsible for the clinical signs and changes seen in Cushing’s.

Contact Surgi-Care Center for Horses at 813-643-7177 or email lkuebelbeck@surgi-carecenter.com with any questions regarding this topic.