Cushing’s Disease Diagnosis

To many horse owners, it’s just old horse disease, and it’s an affliction with a number of names–pituitary pars intermedia dysfunction (PPID), hyperadrenocorticism, ECD (equine Cushing’s disease), and, most commonly, Cushing’s syndrome.

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To many horse owners, it’s just “old horse disease,” and it’s an affliction with a number of names–pituitary pars intermedia dysfunction (PPID), hyperadrenocorticism, ECD (equine Cushing’s disease), and, most commonly, Cushing’s syndrome. It can appear in horses as young as seven, but is most frequently found in horses which are geriatric. Whatever the name, it’s becoming more common in equine populations, due in part to advances in veterinary care and nutrition that help horses lead longer lives.

Equine victims of Cushing’s syndrome (named for turn-of-the-century American surgeon Harvey Cushing, who researched the human brain and pituitary gland) are easily recognized by a heavy, coarse, wavy hair coat that fails to shed in the summer (occurring in more than 85% of cases). Even before that characteristic hair coat appears, a horse with Cushing’s syndrome might demonstrate a host of other symptoms that are sometimes overlooked or chalked up to old age.

The first symptom to appear generally is polydipsia (excessive thirst) coupled with polyuria (excessive urination)–which might go unnoticed if the animal is kept outside rather than stabled. Horses might go through as much as 80 liters of water a day instead of the normal 20 to 30 liters. Other symptoms can include a swaybacked or potbellied appearance, increased appetite (generally with no corresponding weight gain), loss of muscle over the topline, and chronic laminitis. Horses with Cushing’s syndrome become more susceptible to diseases and infections due to a compromised immune system. They frequently suffer bouts of respiratory disease, skin infections, foot abscesses, buccal (mouth) ulcers and periodontal disease, and even infections of the tendon sheath or joints. Wound healing is also noticeably slowed.

Less commonly, a mare’s estrous cycle might be suppressed or abnormal, and she might even produce milk without being pregnant. Some horses become lethargic or depressed, and they frequently acquire an unhealthy gutload of internal parasites, including ascarids (pinworms), which are comparatively rare in adult horses

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Written by:

Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She’s written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.

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