Cushing's Disease in Dogs: Causes, Complications & Medications

Cushing's disease in dogs can cause serious symptoms and complications that can threaten their longevity. Our Greensboro vets explain what causes the condition, as well as complications and treatments.

What causes Cushing's disease (Hyperadrenocorticism) in dogs?

If your dog has a tumor in the pituitary gland, this can lead to an excessive concentration of cortisone in his or her body.

The result: pituitary dependent Cushing’s disease (also known as hyperadrenocorticism), a clinical condition that can put a dog at risk of several serious conditions and illnesses, from kidney damage to diabetes.

What are the symptoms and complications of Cushing’s disease in dogs?

In dogs, the most common symptoms of Cushing’s disease include:

• Excessive thirst or drinking
• Hair loss
• Muscle weakness
• Thin skin
• Pot belly
• Panting
• Lethargy
• Increased appetite

While Cushing’s disease will cause at least one of these symptoms, it’s uncommon to see all of them. Because some of the signs are vague, it’s imperative to see your vet right away if you notice any of them.

Dogs with Cushing’s disease have an increased risk of kidney damage, high blood pressure, blood clots and diabetes.

How is Cushing’s disease diagnosed?

Your vet will only be able to use blood tests to diagnose Cushing’s disease. The tests can include, but are not limited to, a urinalysis, urine culture, adrenal function tests (low dose and high dose dexamethasone suppression test, and potentially ACTH stimulation test), full chemistry panel, and complete blood panel.

At Friendly Animal Clinic, our vets are trained to diagnose and treat a wide range of internal diseases and conditions. We have access to diagnostic imaging tools and treatment methods to identify and manage these issues.

In combination with a physical exam to look for signs of the disease, these tests can help your vet arrive at a diagnosis. Keep in mind that adrenal function tests can result in false positives when another disease with similar clinical signs is present.

Though an ultrasound may help diagnose Cushing’s disease, it’s more valuable in helping to rule out other conditions that could be causing your dog’s symptoms. Other diseases that may cause similar symptoms include tumors in the spleen or liver, bladder stones, gallbladder disease, gastrointestinal disease, chronic inflammatory liver disease.

An ultrasound may not be able to detect adrenal enlargement, since patient movement or interference due to gas in the overlying intestine can influence test results. Most vets prefer magnetic resonance imaging (MRI) - an effective but expensive diagnostic imaging procedure that allows your vet to assess your dog’s adrenal glands.

Are there treatments or medication for Cushing’s disease in dogs?

Currently, two main drugs can treat Cushing’s disease in dogs. A form of the insecticide DDT (drug names include Lysodren^® and mitotane) can destroy the cells that produce cortisone in the adrenal glands.

Other medications such as trilostane help decrease the amount of cortisone that the adrenal glands produce. This accomplishes this goal by inhibiting specific steps in the cortisone production process. Both trilostane and mitotane can effectively treat and control the signs of Cushing’s disease.

Discuss which may be the most effective treatment for your dog, and follow your vet's instructions diligently.

After the induction phase with mitotane, you will need to bring your dog to our clinic for an ACTH stimulation test, which “stimulates” the adrenal gland. This test can be done on an outpatient basis to help your vet determine the starting point for a mitotane maintenance dose. If the mitotane is working, the adrenal gland will not overreact to the stimulation.

Though you won’t need an induction phase for trilostane, dogs often require small adjustments to trilostane doses early in treatment. Over their lifetime, routine monitoring of blood tests may indicate that other adjustments need to be made. How well clinical symptoms of Cushing’s disease can be controlled can also mean changes are required.

No matter the medication, your dog will likely be on it for the long term, and may require periodic adjustments in doses. He or she will need to come in for ACTH stimulation tests as often as monthly until we can control the excessive production of cortisone. Regular testing will be needed.

Adverse Reactions & Prognosis

With diligent observation and long-term management, the symptoms of Cushing’s disease can be minimized. When provided in proper dosage, medication for Cushing’s disease can prove very effective in treating the condition. However, the wrong dose can cause mild or severe side effects.

With blood test monitoring, it’s unusual for adverse reactions to appear. But if they do, they may include:

• Lethargy, depression or weakness
• Gastrointestinal (stomach) upset - diarrhea or vomiting
• Picky eating, eating slowly (taking longer than normal to eat or leaving food), or decreased appetite

If you notice any of these symptoms, discontinue the medication and call your veterinarian right away.

While medication costs and the need for frequent blood monitoring can make Cushing’s disease expensive to manage, diligent follow-up care and monitoring for adrenal function can make for a good prognosis.

Pets who do not receive adequate monitoring and follow-up often experience relapses and severe illness or death, as a result of complications.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.