What Is Cushings Disease in Horses?

By Jen Davis

Cushing's disease is a condition that occurs in horses when the pituitary gland becomes overactive. Cushing's disease may also be referred to as pituitary pars intermedia dysfunction or PPID. Horses with Cushing's disease display several telltale symptoms and require specialized medical care for the rest of their lives.

Cushing's Causes Hormonal Imbalance

Cushing's disease occurs when the function of the pituitary gland is disrupted and the gland begins to send wrong signals to a horse's body. As a result, the horse's body will secrete hormones that he does not need and that can affect the body negatively. One of the hormones commonly secreted in excess is cortisol. The presence of too much cortisol in your horse's system will cause the immune system to become suppressed, leading to a host of other health issues.

Hirsutism Isn't the Only Symptom

Cushing's disease rarely occurs in horses under the age of 7 years; the disease primarily affects horses between 18 and 23 years old. Hirsutism is one of the most easily recognized symptoms associated with Cushing's disease. Hirsutism causes a horse to develop a long, thick and sometimes curly coat. The coat may be slow to shed or may shed improperly.

In addition to experiencing coat changes, horses with Cushing's disease often develop excessive thirst and will urinate excessively as a result. Other symptoms include laminitis, weight loss, mouth ulcers and changes in body shape. Infections may occur; wounds and injuries may be slow to heal.

Blood Testing Provides Definitive Diagnosis

Your horse's medical history and physical appearance will play key roles in diagnosing Cushing's disease. Some veterinarians may diagnose a horse with Cushing's disease based solely on the physical presentation of known symptoms; a more definitive diagnosis requires blood tests. A general blood profile rules out other conditions; specialized followup blood tests will identify Cushing's disease. One blood test used to diagnose Cushing's measures cortisol in the blood before and after administration of a steroid called dexamethasone, which suppresses cortisol levels. Horses with Cushing's disease react to the steroid, and their cortisol levels remain elevated, confirming the disease's presence.

Manage Cushing's With Meds and Maintenance

Cushing's is incurable, but the disease and its symptoms are manageable. Pergolide, a medication for helping manage Cushing's, works by reducing the amount of cortisol a horse is producing. Cyproheptadine, bromocriptine and trilostane manage Cushing's disease with varying levels of effectiveness.

Preventative maintenance -- such as regular farrier care, routine deworming and regular vaccinations -- helps thwart complications from developing. Your vet may recommend horse feeds low in starch and sugars, because a horse with Cushing's will have difficulty processing them. Talk with your veterinarian about any changes to your horse's diet.