Canine Cushing’s Disease

Cushing’s Syndrome is usually discussed under the heading of dermatologic (skin) diseases, but it’s much more than that.

Named after Dr. Cushing who was the leading neurosurgeon of the early 20th century, and who first described the disease as being caused by a tumor of the pituitary gland in the brain, the more descriptive term for the condition is hyperadrenocorticism. Whew! That’s a mouthful, isn’t it? Let’s break the word down to its parts. Hyper is a prefix meaning increased. Adreno refers to the adrenal gland. Corti refers to the cortex or outer portion of the adrenal gland.

There are several forms of the disease. The most common is the first identified by Dr. Cushing, a pituitary tumor, thus the moniker: PDH, pituitary-dependent hyperadrenocorticism. These are almost always benign brain tumors, but they produce an excess of a hormone, ACTH, adrenocorticotropic hormone. ACTH in the bloodstream has the effect of causing the adrenal glands, small glands near the kidneys, to produce excessive amounts of cortisol, another hormone. Excess cortisol, then, causes the damage that results in the signs we see on the outside of the body, indicating the damage that rages within.

A less common form of the condition results from a tumor in the adrenal glands themselves. However, this tumor is almost always cancerous, the cancer is quick to spread, and usually results in a short course of disease.

The condition occurs in cats, but is much more common in dogs. The first signs typically seen are increased thirst and urine output, sagging belly, muscle wasting and weakness, obesity, exercise intolerance and panting, even when not exercising. The skin will exhibit hair loss that is usually the same on both sides, comedomes (blackheads), especially on the abdomen, sometimes with calcium deposits and a black pigment deposited in the skin. The patient’s skin will often be thin (even see-through) dry, wrinkled and flaky.

Because the condition results in an overabundance of production of cortisol, the immune system can be suppressed, leading to recurrent infections of the skin and other parts of the body, as well as overproduction of glucose (sugar) in the bloodstream, overwhelming the pancreas and leading to diabetes mellitus.

Treatment, of course, is aimed at reducing the overproduction of cortisol, usually with medications that attack the adrenal glands. Patients with PDH may use one of two medications. The traditional treatment is given 1-3 times weekly. Alternatively, a newer, once-daily medication is available at about the same cost but with fewer side effects.

Cushing’s disease requires careful monitoring, and frequent visits to your pet’s doctor for follow-up testing.

Both medication and monitoring can be expensive, so plan on budgeting for pet health care if your pet is diagnosed with hyperadrenocorticism.

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