Cushing's Syndrome in Dogs

Cushing’s disease causes excess cortisol in dogs.

Cushing's syndrome or disease is a condition in dogs in which the adrenal glands become overactive, producing too much cortisol.

What Is Canine Cushing's Disease?

Also called hyperadrenocorticism, Cushing's syndrome occurs in dogs when the adrenal glands, which are responsible for producing cortisol, become overactive.

The adrenal glands are located near the kidneys, and their job is to produce several hormones including cortisol and regulate a number of body functions.

When the adrenal glands overwork, they produce too much cortisol. Normally, the adrenal glands release cortisol in response to stress, and the cortisol causes the body to be ready to fight or flee. Cortisol causes a dog's body to begin to burn fat and sugar and retain water. When too much cortisol is continually released, it has negative effects on body functions.

Signs of Cushing's Syndrome in Dogs

The signs of hyperadrenocorticism in dogs include:

Signs of Cushing's syndrome in dogs usually come on slowly and aren't always obvious. Many times, they are written off as normal aging, since Cushing's is more common in older dogs.

Types of Cushing's Disease in Dogs

There are three ways that Cushing's syndrome can develop in dogs, and they have different treatments. They are:

Diagnosing Cushing's Syndrome in Dogs

Diagnosis of Cushing's disease in dogs can be complicated. Your veterinarian may find certain "flags" in baseline bloodwork that, together with physical exam and history findings, indicate that more specific testing should be done on adrenal gland function. These flags include:

It's possible that the doctor will next recommend a urine cortisol/creatinine ratio (UCCR) test for your dog. This is another screening test and does not confirm Cushing's disease. However, if the test is negative, it does rule Cushing's disease out, so further, more expensive testing need not be performed. The test looks for high amounts of cortisol being removed from the body in the urine.

Specific tests for Cushing's disease include:

Once Cushing's disease is diagnosed, an abdominal ultrasound may be done to attempt to differentiate a pituitary-dependent cause from an adrenal-dependent cause. If an ultrasound shows both adrenal glands are roughly the same size, smooth, and both enlarged, pituitary-dependent Cushing's is most likely. If one adrenal gland is significantly larger than the other and isn't smooth, adrenal-dependent Cushing's is most likely.

Treatment of Cushing's Disease in Dogs

The treatment for Cushing's disease in dogs usually depends on whether it is pituitary-dependent or adrenal-dependent.

Adrenal-dependent Cushing's disease may be treated by surgically removing the tumor. Further treatment may be necessary if the tumor is malignant.

Pituitary-dependent Cushing's disease is treated with medications. Lysodren and trilostane are the most common medications used.

Other medications for Cushing's disease are sometimes used when Lysodren or trilostane are deemed too risky or expensive. However, none are as reliable at treating Cushing's.

Dogs with iatrogenic Cushing's disease are treated by slowly withdrawing the external steroid that has caused the problem. These dogs must be watched closely, as well, to ensure that their cortisol doesn't get too low, which can result in collapse and death.

Some dogs with Cushing's disease are not treated. If they have a good quality of life and their illness does not produce signs that are particularly bothersome for the dog or owner, treatment may not be pursued due to the potentially life-threatening side effects of driving the cortisol too low.

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