Cushing’s Syndrome

By: Heather McCauley, DVM

TVMA Member
Rockwall, TX

Published March 2015

Your very well-housebroken dog has had a few “accidents” in the house. He’s in decent shape for his age, but is that the start of a pot-belly? He might even be drinking a bit more lately, but then again, it’s been a hot summer…

Or he could have Cushing’s syndrome.

Cushing’s is a disorder of the adrenals, which are two tiny glands that sit near the kidneys. They produce cortisol, the “stress” hormone. Normally the adrenal glands work in tandemAlongside each other; together. with the pituitary, an even smaller gland at the base of the brain. When cortisol is needed, the pituitary sends a chemical signal to the adrenals, and they increase production. When the pituitary detects a sufficient rise in cortisol levels, it stops stimulating the adrenals and production falls again. Imagine an internal widget factory with the pituitary as Plant Manager, producing hundreds of widgets for the widget store—production ramps up when sales are good and cuts back when demand is low.

Occasionally this system runs amok, and cooperation between the pituitary and the adrenal gland is disconnected. There are two possibilities: Either the pituitary is inappropriately telling the adrenals to over-produce, or the adrenal production is operating overtime in defiance of pituitary control. The end result is that widgets are produced faster and faster, regardless of need. Soon the body is flooded with excess cortisol. The earliest signs are increased urination and increased appetite.

What are the Signs of Cushing’s Syndrome?

Excessive thirst is simply a compensation for excessive urination, therefore restricting water should never be used as a method of reducing “accidents.” It will not work, and the animal will only become dehydrated. This could damage kidney function.

As the condition continues and the cortisol oversupply becomes more frequent or even constant, other consequences develop, including stubborn bacterial infections, an enlarged liver, diabetes, high blood pressure, clotting problems, muscle wasting, osteoporosis, thin skin, fragile tendons and ligaments and a sparse hair coat on the trunk that spares the head and legs. Many patients harbor hidden bacteria in their urine, which is easily missed because the dilute urine looks “clean” on urinalysis, while frequent and excessive urination masks clinical signs of urinary tract infection.

How Does a Veterinarian Diagnose Cushing’s?

Diagnosis is by blood and urine testing and sometimes a non-invasive, painless abdominal ultrasound. The object is first to rule Cushing’s in or out and, if confirmed, to determine whether the fault lies with the adrenal or pituitary gland.

What Causes it?

The most common cause is a microscopic tumor in the pituitary. Using oral medications, the adrenal over-production can be reduced and maintained at an acceptable level in spite of the pituitary’s malfunction. The pituitary tumor itself usually does not grow and so may remain without specific treatment.

Much less commonly, there may be a cortisol-producing tumor in one of the adrenal glands. Adrenal tumors are much less responsive to the pills, so removal is usually recommended. Surgery near the kidneys and major vessels is extremely delicate, so early intervention by an experienced surgeon gives the best chance at success.

Finally, Cushing’s syndrome can be a side effect if cortisone or cortisone-like drugs are administered long-term. It is also seen when owners use topical steroid medicines for their own hormone therapy and the dog has contact with their medicated skin. These medications, whether in oral, injectable or topical (cream, ointment or spray) form, should be used carefully and only under the advice and supervision of your veterinarian.

Naturally occurring Cushing’s is most common in small breeds and middle-aged or older dogs. The condition progresses slowly, with changes so subtle they may be nearly invisible to someone who sees the dog every day. Yearly or twice-yearly exams will expose these trends and allow successful treatment. This is a disease that can be well-managed to provide your dog with a good quality of life.

Heather McCauley, DVM, is a graduate of University of Florida College of Veterinary Medicine who lives near Rockwall, Texas. Dr. McCauley practices as a relief veterinarian serving the eastern Dallas metroplex to Tyler areas for McCauley Veterinary Services.

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