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Health Matters
April 6, 2011
Some diseases and disorders have been in the public mindset for years and we seem to have a basic understanding of them even if we have no firsthand experience. Then there are "new" health problems with new names that are just becoming more commonly talked about - Cushing's is one of those diseases. This month Ann explores what Cushing's disease is and how it affects dogs, horses and (very rarely) cats - and, importantly, what are the treatments.
*Standard disclaimer: while we will offer our opinions about how to best achieve optimum health for our animals, we do NOT profess to know what is better for your pet than you or your vet do! Always consult with your vet, then consult with another vet and get a second opinion (because we also believe in having options!).
Cushing's Disease
This month we look at another hormonal (endocrine system) imbalance. Cushing’s is frequently misdiagnosed by the owner as signs of old age, when in fact, it is an endocrine dysfunction/condition fairly common in older horses and dogs. It is seen in cats rarely, and then usually associated with diabetes. It is treatable and generally not life-threatening. However, the sooner it is diagnosed, the better it is for your pet and the easier his road to recovery.
Cushing's Disease is named for the human physician, Dr. Harvey Cushing, who first described the symptoms in 1932. It is scientifically known as hyperadrenocorticism, which means over production of the adrenal hormones called corticosteroids. There are three ways that an animal can get Cushing’s: It can be caused by the over administration of corticosteroids such as prednisone, in which case it is easy to cure ~~ just cut out the corticosteroid, slowly allowing the body to return to normal. Naturally occurring Cushing’s can happen in two ways and is not so easy to handle. Hyperadrenocorticism happens when the adrenal gland goes into overdrive. This usually (85% of the time) is the result of a benign pituitary tumor which causes the pituitary to produce too much ATCH which causes the adrenal gland to go into over production. The other cause (15% of the time) is a benign tumor of the adrenal gland itself.
Corticosteroids are a class of steroid hormones that are involved in a wide range of physiologic systems such as stress response, immune response, regulation of inflammation, carbohydrate metabolism, protein metabolism, blood electrolyte levels, and behavior. These can be broken down into two classifications: Glucocorticoids (such as cortisol) that control carbohydrate, fat, and protein metabolism and are anti-inflammatory by preventing phospholipid (Any of various phosphorus-containing lipids, such as lecithin and cephalin, that are composed mainly of fatty acids) release, decreasing eosinophil (white blood cells or leukocytes) action etc. Mineralocorticoids such as aldosterone which control electrolyte and water levels mainly by promoting sodium retention in the kidneys.
Cushing’s in Dogs
Canine Cushing’s disease normally affects middle-aged to older dogs (7 – 12) and some breeds seem to have a predilection. Miniature Poodles, Dachshunds, Boxers, Boston Terriers, and Beagles have an increased risk of this disease. The symptoms progress slowly, often mistaken by owners of signs of old age. Common signs include increased drinking and urination, abdominal swelling (pot belly) and hair loss. Some dogs develop lesions and have recurrent urinary tract infections. Other symptoms include thinning skin, calcified lumps in the skin, diabetes, and weakening of the heart and skeletal muscles.
Treatment is dependent upon where the trouble originates. There are several tests that must be done to determine the location of the cause: pituitary or adrenal gland. If the cause is a tumor in the adrenal gland (15%) then it can be surgically removed or medically treated to kill off the outer layers. The dog may then have to be on replacement hormones for the rest of its life. If the cause is a tumor in the pituitary gland (85%), then the treatment becomes symptomatic therapy, generally aimed at providing a better quality of life.
Cushing’s in Horses
Cushing’s is a fairly common disease in older horses, often mares and ponies. It is caused by hyperplasia (enlargement) or adenoma (benign tumor) in a portion of the pituitary called the pars intermedia. Therefore the more accurate term is Pituitary Pars Intermedia Dysfunction. It is characterized by a long hair coat that doesn't shed in the summer, laminitis or founder of the feet, and usually a crusty neck and large fat deposits around the head of the tail. Other symptoms include weight loss/muscle loss particularly across the topline, which may be accompanied by a pot belly appearance. The horse may also have increased thirst and urination, a ravenous appetite, and lethargy
The main concern is that founder can be deadly; however recent veterinary medicinal findings show that an increase of lipofuscin, an aging pigment, accumulates in the nervous system, liver, and heart and can lead to other medical problems. A lung inflammation called bronchiolitis makes Cushing’s horses more susceptible to lung infections.
Few horses have been treated successfully, but daily medicine may be beneficial. Pergolide has been used successfully in a few horses on a daily dosage. One horsewoman, Nina Arbella, has had success by treating her horses with chasteberry. She is founder and president of Eye of the Storm Equine Rescue of Stow, Massachusetts. Her story can be found at www.alphahorse.com. She suggests feeding “one teaspoon of ground chaste (tree) berry twice a day with their feed. Give it to them three weeks on and one week off all year round.” She also gives them all “vitamin E in the evening and vitamin C in the morning and MSM. No sugars or carbohydrates (not even a carrot).”
Cushing’s in Cats
Cushing’s Disease is fairly uncommon in cats. Most often (85% of the time) a tumor presents itself on the pituitary gland at the base of the brain. The symptoms include poor coat appearance, increased thirst and appetite, increased urination, decreased muscle capability, thinning of the skin and weight gain. Personality changes have also been noted.
A medication called metyrapone can sometimes be beneficial, and surgery is sometimes the only effective option. Surgery consists of the removal of one or both of the adrenal glands. The cat will them require medication indefinitely to replace the hormone that can no longer be produced naturally.
Cushing’s reminds me of a car filled with the wrong type of gasoline and/or oil. Too rich a mixture stresses the engine, which has to work harder to maintain normal function; over time, the engine begins to get too hot, bogged down, pressure builds further damaging hoses and belts and eventually the entire motor breaks down and ages prematurely. Fortunately for us, our bodies and our pets’ bodies are incredible machines, designed to run for years with nominal care and prudence. Our hormones regulate us, we need them, but our exposure to them must fall within certain parameters for our bodies to work well. If you see your pet exhibiting any of the signs mentioned above, it could be “just old age” but it never hurts to make sure nothing is amiss during your pet’s annual health exam. If what you chalk up to age is in fact a easily treatable hormonal imbalance, imagine the quality years you add to your pet’s life by finding out his “old age” is Cushing’s Disease.
