You’ve probably noticed the changes. Your dog, who used to be the pickiest eater in the neighborhood, is suddenly acting like they haven't seen a meal in weeks. They’re drinking so much water you’re refilling the bowl three times a day. Maybe their belly looks a bit rounder—sort of a "pot-bellied" look—even though their legs seem thinner. It’s easy to shrug it off as "just getting old."
But it’s usually not just age.
When a dog’s body starts overproducing cortisol, things get weird fast. This hormonal overdrive is known as hyperadrenocorticism, but most of us just call it Cushing’s disease. It’s a complex, frustrating condition that creeps up on you. Understanding what causes Cushing disease in dogs is the first step toward getting your sanity—and your dog’s health—back on track. Honestly, it’s a bit of a biological glitch where the body’s "fight or flight" system gets stuck in the "on" position.
The Glitch in the System: How Cortisol Goes Rogue
Cortisol isn't the villain here. Not normally. In a healthy dog, the adrenal glands—two tiny, bean-shaped powerhouses sitting right next to the kidneys—pump out cortisol to help the body manage stress, regulate blood sugar, and fight inflammation. It’s vital.
The problem starts when the feedback loop breaks.
Think of it like a thermostat in your house. Usually, when the room gets warm enough, the heater shuts off. With Cushing’s, the heater just keeps blasting. The dog’s body is flooded with steroids 24/7. This constant bath of cortisol begins to break down muscle, thin out the skin, and put immense pressure on the liver. It's exhausting for the dog. They aren't just "hungry"; their metabolism is literally screaming for fuel because the hormones are mismanaging how energy is used.
The Pituitary Culprit (The 85% Rule)
Most of the time—roughly 80 to 85 percent of cases—the root cause isn't even in the adrenal glands. It’s in the brain. Specifically, a tiny pea-sized gland called the pituitary gland.
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A small, usually benign tumor (an adenoma) develops on the pituitary. This tumor starts screaming orders at the adrenal glands. It produces an excess of Adrenocorticotropic Hormone, or ACTH. When the adrenal glands receive all that ACTH, they do exactly what they’re told: they churn out cortisol.
The adrenal glands actually get bigger because they’re working overtime. They’re like bodybuilders on a permanent cycle. Even though the tumor is usually microscopic and doesn't cause "brain" problems, the hormonal fallout is massive. Interestingly, smaller breeds like Poodles, Dachshunds, and Boston Terriers are the usual suspects for this specific version.
When the Adrenals Act Alone
Then you have the other 15 percent. This is Adrenal-Dependent Cushing’s. In this scenario, the "orders" from the brain are totally normal. The pituitary is behaving itself. Instead, a tumor has formed directly on one of the adrenal glands.
These tumors can be a coin toss. About half are benign (adenomas), and the other half are malignant (carcinomas). When it’s a carcinoma, there’s a risk it could spread to the liver or lungs, which makes the situation a lot heavier. Large breed dogs—think Labradors or German Shepherds—tend to see this version more often than the little guys.
The "Oops" Cause: Iatrogenic Cushing’s
There’s a third cause that’s actually preventable, and it’s a bit of a gut-punch for owners. It’s called Iatrogenic Cushing’s.
Basically, we cause it.
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If a dog has been on high doses of oral steroids or long-term steroid injections for allergies, skin issues, or arthritis, their body can start exhibiting Cushing’s symptoms. The body doesn't distinguish between the cortisol it makes and the prednisone you’re giving it. The result is the same: steroid overload. The weird twist here is that while the dog looks like they have Cushing’s, their own adrenal glands have actually shriveled up (atrophied) because they haven't had to do any work for months.
Why Diagnosis Is Such a Headache
You can't just run a simple blood test and get a "yes" or "no" answer. It’s never that easy.
Veterinarians usually start with a "suspicion" based on the pot-belly and the excessive drinking (polydipsia). But because cortisol levels fluctuate wildly throughout the day, a single snapshot doesn't tell the whole story.
Most specialists, like those at the American College of Veterinary Internal Medicine (ACVIM), recommend a series of "stress tests" for the glands. The most common is the Low-Dose Dexamethasone Suppression (LDDS) test. They give the dog a tiny bit of synthetic steroid and watch how the body reacts over eight hours. A healthy body says, "Oh, I have enough steroids now, I'll stop making cortisol." A Cushingoid dog’s body just ignores the signal and keeps pumping it out.
There's also the ACTH Stimulation test, which is faster but sometimes less sensitive for certain types of tumors. It's expensive. It’s time-consuming. And sometimes, the results are "equivocal," which is just a fancy way of saying "we still aren't sure."
Signs You Might Be Overlooking
It’s easy to focus on the hunger, but Cushing’s writes its story all over the dog's skin.
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- Thin Skin: If you can see the blood vessels on your dog's belly more clearly than before, that's a red flag.
- Hair Loss: It’s usually symmetrical. The fur thins out on the flanks and the trunk, but the head and legs stay fuzzy.
- Blackheads: You might see weird little black specks or "calcinosis cutis"—hard, gritty calcium deposits under the skin that feel like little stones.
- Panting: Even when it’s cool in the house, a Cushing’s dog might pant like they’ve just run a marathon.
These symptoms aren't just annoying; they're signs of a body under siege. The high cortisol levels are weakening the immune system, making these dogs prone to frequent urinary tract infections (UTIs) that just keep coming back.
Is It Worth Treating?
This is the hard part. Cushing’s isn't usually "cured"—it's managed.
If it’s a pituitary tumor, surgery is rarely an option because, well, it’s brain surgery on a dog. Instead, we use medications like Trilostane (Vetoryl) or Mitotane. These drugs basically act as "production blockers," chemically telling the adrenal glands to chill out.
Trilostane is the modern go-to. It’s generally safer but requires regular blood monitoring to make sure you don’t swing the pendulum too far the other way and cause Addison’s disease (too little cortisol).
If it’s an adrenal tumor and it hasn't spread, surgery to remove the affected gland can actually be curative. It's a big, risky surgery, but it can add years to a dog's life.
Practical Next Steps for Owners
If you suspect what causes Cushing disease in dogs is currently happening under your roof, don't panic, but don't wait.
- Track the Water: Start measuring exactly how much your dog drinks in a 24-hour period. "A lot" is hard for a vet to quantify. "Three bowls" is better. "Two liters" is perfect.
- Check the Meds: Look at your dog's recent history. Have they been on Prednisone, Temaril-P, or steroid ear drops lately? Tell your vet exactly what and for how long.
- Request a Urinalysis: Before diving into $500 endocrine tests, check the urine. Dogs with Cushing’s often have very "dilute" urine because their kidneys are struggling to keep up with all that water.
- Manage Expectations: Treatment is a marathon. It involves frequent vet visits for the first six months to dial in the dosage. It’s also pricey.
The goal isn't to make the dog live forever. The goal is to stop the insatiable thirst, heal the skin, and let them sleep through the night without needing a bathroom break every two hours. Most dogs on proper treatment regain a fantastic quality of life and go back to being their old, happy selves—just maybe a little less obsessed with the treat jar.
Keep a close eye on their energy levels. If the treatment makes them lethargic or causes vomiting, that’s an emergency—it means their cortisol has dropped too low. Balance is everything.