The challenge with Cushing's disease is that it doesn't announce itself. There is no sudden collapse, no dramatic crisis. Instead, it arrives the way most chronic conditions in older dogs arrive: gradually, ambiguously, easily mistaken for something else entirely.
By the time most dogs are formally diagnosed, they've been showing signs for months — sometimes years. The condition is often described as "silent" because the early symptoms blend so seamlessly into normal aging that even attentive owners can miss them. Cornelius was no different. The first signs were easy to rationalize.
This guide walks through what Cushing's disease looks like at every stage — from the subtle things that shouldn't concern you yet, to the unmistakable ones that mean you should call your vet today.
What Is Cushing's Disease, Briefly
Cushing's disease (hyperadrenocorticism) occurs when a dog's body produces too much cortisol — the stress hormone that, in normal quantities, helps regulate metabolism, immune response, and blood pressure. Cortisol is essential. Too much of it, sustained over months and years, is corrosive.
In roughly 85% of cases, the root cause is a small tumor on the pituitary gland at the base of the brain. That tumor keeps pressing the signal that tells the adrenal glands to produce cortisol. In the remaining ~15% of cases, the tumor is in one of the adrenal glands themselves. Either way, the result is the same: cortisol levels that never properly shut off.
This matters for symptoms because cortisol touches nearly every system in the body. When it stays elevated, the effects show up in the skin, the liver, the muscles, the immune system, and the way a dog drinks, eats, and behaves. You'll see it in all of them.
The Three Stages of Symptoms
Not every dog moves through these stages in the same order or at the same speed. Some dogs plateau at Stage 1 for years; others progress faster. Think of these as overlapping zones, not rigid categories.
Subtle enough to dismiss
- Drinking slightly more water than usual (hard to notice if you're refilling bowls without measuring)
- Panting more often, especially after light activity or in cool weather
- Slightly increased appetite — finishing meals faster, looking for more
- More frequent urination — needing to go out more or having accidents indoors
- A little more tired than usual after walks
Harder to rationalize
- Clear increase in thirst — finishing water bowls and seeking more
- Persistent, heavy panting even at rest
- Hair loss beginning — typically symmetrical, starting on the flanks, belly, or sides
- Skin thinning and darkening — dark spots appearing, skin feeling papery
- Noticeable muscle weakness — struggling to jump onto the couch, lagging on stairs
- A pot-bellied appearance even with normal eating
- Development of a fatty hump between the shoulder blades
- Increased hunger that borders on insatiable
Immediate vet attention warranted
- Extreme lethargy — barely moving, uninterested in walks or play
- Severe skin infections that don't clear with standard treatment
- Calcinosis cutis — hard, crusty calcium deposits in the skin (distinctive of Cushing's)
- Severe muscle wasting — visible ribcage, thin legs
- Neurological symptoms — circling, head tilting, loss of coordination (suggests pituitary tumor growth)
- Uncontrolled Diabetes developing — a common complication
If your dog is showing two or more symptoms from Stage 2, it's worth asking your vet about testing. You don't need to wait for everything to be severe. The ACTH stimulation test and/or the low-dose dexamethasone suppression test are the standard diagnostic tools — and early diagnosis makes treatment significantly more effective.
The Symptoms That Look Like Something Else
This is where Cushing's gets especially tricky. A lot of its symptoms overlap with conditions that are more common and less alarming:
- Excessive drinking and urination — also signs of diabetes, kidney disease, or a urinary tract infection. This is why vets don't diagnose Cushing's on symptoms alone.
- Hair loss — also seen in hypothyroidism, allergies, and seasonal patterns. Cushing's hair loss is typically symmetrical and bilateral — the same on both sides.
- Increased appetite — also a thyroid symptom. The pot-bellied appearance, though, is more distinctive to Cushing's.
- Panting — also normal in warm weather, in anxious dogs, and in brachycephalic breeds. Cushing's-related panting is persistent and doesn't track with temperature.
The combination of symptoms is what matters. A single symptom means very little. A cluster of four or five from Stage 2 in an older dog — especially a small to medium breed (poodles, dachshunds, terriers, and beagles are over-represented) — is worth investigating.
What the Tests Actually Tell You
You can't diagnose Cushing's from symptoms alone, and your vet can't either. The diagnostic process involves one or more of these tests:
- ACTH Stimulation Test — The most common initial test. Measures how the adrenal glands respond to a synthetic hormone. In Cushing's dogs, cortisol stays elevated. Quick, relatively inexpensive, good for screening.
- Low-Dose Dexamethasone Suppression Test (LDDST) — More sensitive than the ACTH test. Distinguishes between pituitary-dependent and adrenal-dependent Cushing's. Useful when ACTH results are inconclusive.
- Urine Cortisol:Creatinine Ratio — A non-invasive screening test using a urine sample. Good for ruling out Cushing's (a low ratio essentially excludes it), but a high ratio requires follow-up testing to confirm.
- Abdominal Ultrasound — Not for diagnosis, but to check for an adrenal tumor if your vet suspects the ~15% adrenal form. Also evaluates liver health, which is often compromised in Cushing's dogs.
Cornelius's Story
For us, the earliest sign was the drinking. Cornelius had always been a moderate water drinker, and then — seemingly overnight — he was finishing every bowl and standing by the sink. The panting came next, in the evenings, when the house was quiet and there was nothing to explain it.
We rationalized it. He's getting older. It's been a warm week. He's had a long walk. By the time we got him tested, the skin changes had already started — the thinning, the darkening, the patchy hair loss along his sides. We caught it mid-Stage 2, which is where most owners finally get to a vet.
That's why the diagnosis questions are important to push for if you have any reason to wonder. The tests aren't invasive, and knowing what you're dealing with changes the entire treatment path — and the timeline you're working with.
Next Steps
If you've recognized some of these signs and you're wondering whether to schedule a test, the short answer is yes. The earlier you know, the more options you have. Read our guide on treatment options for Cushing's disease in dogs to understand what comes next.
If you're already managing a Cushing's diagnosis and the costs are a concern, learn about the real monthly cost of care — and how the Cornelius Fund is working to help families in the same position.