Cushing's Disease in Dogs: Signs, Diagnosis, and Treatment

What causes it

There are three main forms, and vets need to know which one a dog has because treatment differs. The most common is pituitary-dependent Cushing's, which accounts for roughly 85 percent of natural cases. A tumor in the pituitary gland, at the base of the brain, releases too much of the hormone that tells the adrenal glands to make cortisol. These tumors are usually small and benign, though some grow larger over time.

In roughly 15 percent of natural cases, the problem is a tumor in one of the adrenal glands. The tumor makes cortisol on its own. About half of these adrenal tumors are benign, and about half are malignant.

The third form is caused by medicine. Long-term use of steroid drugs, for example for allergies or immune diseases, can produce the same signs. Vets call this iatrogenic Cushing's.

Cushing's disease is most often diagnosed in middle-aged and older dogs. It can occur in any breed. Miniature Poodles, Dachshunds, Boxers, Boston Terriers, and Beagles are among those affected more often. It is a hormone problem, so it does not spread to other pets or to people.

Signs to watch for

Signs build up over months, and a dog may show only a few of them at first.

• Drinking much more water and urinating more, sometimes with accidents in the house
• A bigger appetite, including begging or stealing food
• A rounded, sagging belly, often called a pot belly
• Thinning hair, bald patches, or a dull coat
• Thin skin, easy bruising, dark patches on the skin, and wounds that heal slowly
• Repeated skin infections or bladder infections
• Heavy panting, even at rest, and trouble coping with heat
• Muscle loss, weakness, and low energy, often noticed as trouble with stairs or jumping

Less often, a dog develops small, firm, gritty spots in the skin, often on the belly. They are caused by mineral deposits, and vets call this calcinosis cutis. High cortisol can also raise blood pressure, and some dogs go on to develop diabetes, so vets often check for these too.

Many of these signs overlap with other conditions, such as diabetes, kidney disease, or skin allergies. That is one reason testing matters.

When it is an emergency

Cushing's disease itself develops slowly, but some situations need urgent care. Contact your veterinarian or an emergency clinic the same day if you notice any of the following.

• Collapse, sudden severe weakness, or being unable to stand
• Sudden trouble breathing, which in dogs with this disease can be caused by a blood clot in the lungs
• Refusing food, vomiting, or diarrhea together with weakness or tiredness, especially after starting treatment
• Seizures, walking in circles, confusion, or other sudden changes in behavior
• Straining to pass urine with little or nothing coming out

Treatment lowers cortisol. If cortisol drops too low, a dog can become seriously ill, and in some dogs the medicine can damage the adrenal glands, sometimes for good. Ask your vet what to do if these signs appear, and keep that advice written down at home.

How vets diagnose it

There is no single simple test for Cushing's disease. Vets usually build the picture in steps.

The first step is a physical exam and routine tests. These usually include a complete blood count, a blood chemistry panel, a urine test, and often a blood pressure check. Dogs with Cushing's disease often have a raised liver enzyme called alkaline phosphatase, dilute urine, or signs of a bladder infection. These results raise suspicion but do not confirm the disease.

If the signs and early results fit, the vet moves on to hormone tests. The most common are the low-dose dexamethasone suppression test and the ACTH stimulation test. Both measure how cortisol levels respond to an injection, with blood samples taken before and after. The low-dose test takes about eight hours, so your dog may spend the day at the clinic. A urine cortisol test is sometimes used first, because a normal result makes Cushing's disease unlikely.

Stress and other illnesses can affect these results. A dog that is sick with something else may test positive without having Cushing's disease. For this reason, vets test only dogs whose signs fit the disease. If results are unclear, the vet may suggest repeating the tests in three to six months.

Once the disease is confirmed, the next step is to find where it comes from. An abdominal ultrasound can show whether one adrenal gland has a tumor or both glands are enlarged, which points to the pituitary. Some dogs also need further blood tests, X-rays, or a CT or MRI scan at a referral center.

How it is treated

Treatment depends on the cause and on the dog's overall health. The aim is to control the signs and give the dog a good quality of life.

Most dogs with the pituitary form are treated with daily medication that reduces how much cortisol the adrenal glands make. The medicine controls the signs without curing the disease, so treatment is usually lifelong. Thirst, appetite, and panting often improve within a few weeks, while the coat and skin can take several months.

For an adrenal tumor, surgery to remove the affected gland is often the preferred treatment when it is possible. It is a major operation, usually done by a specialist surgeon, and it can cure a dog with a benign tumor. The outlook is more guarded for malignant tumors, especially if they have spread. When surgery is not an option, medication can help control the signs.

For the pituitary form, radiation therapy or pituitary surgery are offered at some specialist centers. Radiation is mostly considered when the pituitary tumor is large.

Iatrogenic Cushing's is managed by reducing the steroid medicine. This needs to happen slowly and under your vet's guidance, because stopping steroids suddenly can make a dog seriously ill. The condition the steroid was treating may also need a new plan. Please talk to your vet before changing or stopping any steroid.

Some dogs have only mild signs when the disease is found. Ask your vet whether treatment is needed now or whether regular monitoring is enough for your dog.

Living with a dog on treatment

Treatment works best with close follow-up. Your vet will schedule blood tests in the first weeks after starting medication and after any dose change, then usually every few months once the dog is stable. These checks show whether cortisol is in the right range.

Give the medicine the way your vet recommends, including whether it should be given with food. Keep fresh water available at all times. Restricting water can harm a dog with this condition, even when it seems to help with accidents in the house. Offer more trips outside instead, and ask your vet before making any change. A simple diary of how much your dog drinks, eats, and sleeps is useful, because changes in these habits are often the first clue that treatment needs adjusting.

With good control, many dogs feel much better and have a good quality of life. How long a dog lives depends on the cause, the dog's age, and any other health problems. Your vet can explain what to expect for your dog.

Prevention

The natural forms of Cushing's disease cannot be prevented. What owners can do is notice the early signs and book a checkup. Regular exams for older dogs, with blood and urine tests when your vet recommends them, help find hormone problems sooner.

The steroid-related form can often be avoided. Steroids are very useful medicines. Give them only as prescribed, keep to the planned length of treatment, and ask your vet about follow-up checks if your dog needs them long term.

Adopted and rescued dogs

Rescued and newly adopted dogs often arrive with little known medical history. An older dog may have had steroid treatment in the past, and a thin coat, a round belly, or constant hunger can easily be put down to a hard start in life. At Paw Squadron, the first stops after every rescue are the vet and a bath, and every animal gets a checkup, treatment, vaccinations, and a microchip before adoption. Cushing's disease develops slowly, though, so signs may only appear months or years after a dog settles into a new home.

If you adopt a middle-aged or older dog, share any records you received with your own veterinarian and mention changes in thirst, appetite, or coat early. If you are thinking about giving an older dog a home, our Adoptions page is a good place to start, and you can find more health guides in PawPedia.