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Treating Cushing's Disease in Dogs

In December 2008, the Food and Drug Administration (FDA) approved
the first drug in more than 10 years to treat Cushing's disease in dogs.

Hyperadrenocorticism, commonly known as Cushing's disease, is a
condition that results when the body produces too much of a hormone
called cortisol. Cortisol is produced and stored by the adrenals, two
small glands that sit on top of the kidneys.

Dogs, cats, and horses, as well as humans, can get Cushing's disease. It
is more commonly found in dogs than in cats or horses.

"Cortisol is one of the body's natural steroids," says Ann Stohlman,
V.M.D., a veterinarian in FDA's Center for Veterinary Medicine, adding
that a normal amount of cortisol is good. "It helps the body adapt in
times of stress." Cortisol also helps regulate proper body weight,
tissue structure, skin condition, and other features of good health.

But too much cortisol weakens the immune system, leaving the body
vulnerable to other diseases and infections.

Two Common Types
Most canine Cushing's disease occurs naturally and is either pituitary-
dependent or adrenal-dependent. About 80–85 percent of Cushing's
is pituitary-dependent, meaning it's triggered by a tumor on the pituitary,
a pea-sized gland at the base of the brain.

The pituitary makes a number of hormones, including adrenocorticotropic
hormone (ACTH). The pituitary tumor causes overproduction of ACTH,
which travels through the bloodstream to the adrenal glands, stimulating
them to produce more cortisol than the body needs.

In the other 15–20 percent of Cushing's dogs, a tumor in one or both
adrenal glands produces excess cortisol.

The type of Cushing's may determine what kind of treatment is
prescribed. Veterinarians use blood tests to diagnose Cushing's and
to differentiate between disease caused by the pituitary or the adrenals.
They may also use an ultrasound to help detect a tumor on an adrenal gland.

Symptoms
Cushing's disease typically occurs in middle-aged to older dogs. The
disease develops slowly and the early signs are not always noticed.
Symptoms in dogs include

increased thirst
increased urination
increased appetite
reduced activity
excessive panting
thin or fragile skin
hair loss
recurrent skin infections
enlargement of the abdomen, resulting in a "pot-bellied" appearance
back to top

Treatment
Most veterinarians treat Cushing's disease with medication. The only way
to "cure" Cushing's disease is to remove the adrenal tumor if the disease
is adrenal-dependent and the tumor hasn't spread, says Stohlman.
However, because of the complexity and risks of the surgery, most cases
are treated with medication. Currently, surgery to remove a pituitary
tumor is not an option.

Although Cushing's is typically a lifelong condition, the disease usually
can be managed with medications. "It's important for a veterinarian
to see the dog regularly and do blood tests," Stohlman says. "Monitoring
the blood helps determine the right dose, which may need to be
adjusted periodically."

Frequent blood tests are usually required in the first few months after
starting treatment and then every few months after that, depending on
the dog's response to treatment and tolerance to the medication.

Vetoryl (trilostane) Capsules, the latest drug approved to treat canine
Cushing's, is also the first drug approved to treat both pituitary- and
adrenal-dependent Cushing's in dogs. This prescription drug works
by stopping the production of cortisol in the adrenal glands. In
studies of the drug, the most common side effects were vomiting,
lack of energy, diarrhea, and weight loss. Vetoryl should not be given
to a dog that
has kidney or liver disease
takes certain medications used to treat heart disease
is pregnant

The safety and effectiveness of Vetoryl were shown in several studies.
Success was measured by improvements in both blood test results
and physical symptoms (increased appetite and activity level, and
decreased panting, thirst and urination).

Only one other drug, Anipryl (selegiline), is FDA-approved to treat
Cushing's disease in dogs, but only to treat uncomplicated, pituitary-
dependent Cushing's.

Veterinarians have often used a human chemotherapy drug, Lysodren
(mitotane), "off-label" to treat Cushing's in dogs. Lysodren destroys
the layers of the adrenal gland that produce cortisol. It requires
careful monitoring and can have severe side effects.

"Off-label," or "extra-label," means veterinarians can legally prescribe
human drugs to animals for uses not listed on the label, or for other
species or at different dosage levels from those listed on the label.
But because dogs may react unpredictably to human drugs, says
Stohlman, it's beneficial to have treatments available that have been
studied in dogs and approved specifically for them.

"Treating Cushing's is a balancing act," Stohlman says. "But dogs with
the disease can live a good life if they are monitored closely by a
veterinarian and the owner is diligent about bringing the dog in for
blood work and giving the medication as directed."

his article appears on FDA's Consumer Health Information Web page (www.fda.gov/consumer), which features the latest updates on
FDA-regulated products. Sign up for free e-mail subscriptions at www.fda.gov/consumer/consumerenews.html.

For More Information
www.fda.gov/cvm/CVM_Updates/DogCushingDisease.htm

Date Posted: May 11, 2009

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