Cushing’s disease in dogs is caused by chronically elevated cortisol — usually from a small tumor on the pituitary or adrenal gland — and it shows up as the “4 P’s”: increased thirst, urination, appetite, and panting. It’s most common in dogs over 8, and while it’s manageable with medication, it’s not something you catch by watching your dog for one bad week. It creeps in over months.
What’s Actually Happening in Your Dog’s Body
Cortisol is a normal, necessary hormone — it regulates metabolism, blood sugar, and your dog’s stress response. Cushing’s disease (the clinical name is hyperadrenocorticism) happens when the body produces far too much of it, for too long.
There are two main causes, according to the American College of Veterinary Internal Medicine (ACVIM):
- Pituitary-dependent Cushing’s (about 80–85% of cases): A small, usually benign tumor on the pituitary gland tells the adrenal glands to overproduce cortisol.
- Adrenal-dependent Cushing’s (about 15–20% of cases): A tumor directly on one of the adrenal glands produces excess cortisol on its own. These are more likely to be malignant than pituitary tumors.
A third, less common form — iatrogenic Cushing’s — is caused by long-term use of steroid medications (like prednisone) rather than a tumor. If your dog has been on steroids for allergies or an autoimmune condition, mention that to your vet early, since the workup is different.
The Signs Owners Usually Notice First
Cushing’s develops slowly, which is exactly why it gets missed or written off as “just getting older.” The classic signs are:
- Drinking noticeably more water and needing to pee more often (sometimes with accidents indoors)
- Increased appetite — acting hungry all the time, even right after a meal
- A pot-bellied appearance, from fat redistribution and weakened abdominal muscles, even without significant weight gain elsewhere
- Thinning hair or bald patches, especially along the flanks and trunk, without itching
- Thin, fragile skin that bruises or takes a long time to heal
- Excessive panting, even at rest or in a cool room
- Muscle weakness or a reluctance to jump or climb stairs
None of these on their own is diagnostic — a dog that’s drinking more could have a dozen other things going on, including diabetes, which shares several of these symptoms and sometimes occurs alongside Cushing’s (we cover the overlap in our guide to diabetes in dogs). That’s exactly why this isn’t a diagnose-at-home condition — it needs bloodwork.
How Vets Diagnose It
There’s no single “Cushing’s test.” Vets typically build a picture using a combination of:
- Baseline bloodwork and urinalysis — dogs with Cushing’s often show elevated liver enzymes (ALP in particular), high cholesterol, and dilute urine, which points the vet toward further testing.
- Low-dose dexamethasone suppression test (LDDS): Considered the most reliable screening test by ACVIM. It measures how the body responds to a synthetic steroid over several hours.
- ACTH stimulation test: Faster and cheaper, but less sensitive — better at confirming a suspected diagnosis than screening for one, and it’s the preferred test to monitor treatment once a dog is diagnosed.
- Abdominal ultrasound: Used to check the size and shape of the adrenal glands and help distinguish pituitary-dependent from adrenal-dependent disease, and to rule out a mass.
This workup takes more than one visit. That’s normal — Cushing’s is genuinely one of the harder endocrine diseases to pin down, and rushing the diagnosis leads to dogs being treated for the wrong thing.
Treatment Options
Treatment depends on which type your dog has:
Pituitary-dependent Cushing’s is usually managed with daily medication rather than surgery, since the tumor is on the pituitary gland deep in the brain. The most commonly prescribed drug is trilostane, which blocks cortisol production at the adrenal gland. Mitotane is an older alternative, still used in some cases. Dogs on either medication need regular monitoring — typically an ACTH stim test at set intervals — because over-suppressing cortisol is dangerous and causes its own set of problems (Addisonian crisis, in the worst case).
Adrenal-dependent Cushing’s may be treated surgically if the tumor is confined to one adrenal gland and hasn’t spread — this can be curative. When surgery isn’t an option (due to the dog’s age, other health issues, or tumor spread), medication is used instead, the same way it’s used for pituitary-dependent cases.
Iatrogenic Cushing’s is treated by slowly tapering the steroid medication under veterinary supervision — never stopped abruptly, which can cause a dangerous cortisol crash.
Most dogs on appropriate treatment see real improvement: less drinking and urinating, better energy, and improved coat within a few weeks to a couple of months. It’s a lifelong management condition, not a cure, but a well-managed dog with Cushing’s can have a good quality of life for years.
Is Cushing’s Actually Dangerous If Left Untreated?
Untreated Cushing’s isn’t usually the direct cause of death, but chronically high cortisol raises real risks over time: high blood pressure, blood clots (including life-threatening pulmonary thromboembolism), increased susceptibility to infections, and diabetes. Left unmanaged, it also steadily erodes quality of life — thinning skin that tears easily, weak muscles, and constant thirst and hunger aren’t trivial for a dog to live with. It’s worth treating even in an older dog, as long as they’re otherwise a reasonable candidate for daily medication and monitoring.
When to See a Vet
Book an appointment if your dog is drinking or urinating noticeably more than usual, has developed a pot-bellied look, is losing hair symmetrically without scratching, or seems unusually hungry all the time. None of these are emergencies on their own, but they’re worth bloodwork rather than waiting to see if it resolves.
Seek care urgently if your dog develops sudden weakness, collapse, labored breathing, or vomiting — these can signal a complication like a blood clot or an Addisonian crisis, particularly in a dog already being treated for Cushing’s whose medication dose may need adjusting.
The Takeaway
Cushing’s disease is a slow-building hormonal condition, not a sudden illness — which is exactly why the early signs (more thirst, more appetite, a rounder belly) get dismissed as normal aging. If your senior dog is drinking more, panting more, or developing that pot-bellied shape, it’s worth a vet visit and bloodwork rather than waiting it out. Diagnosis takes some patience, but treatment is genuinely effective, and most dogs on trilostane or post-surgical management go on to feel noticeably better. If weight has crept up rather than the belly shape changing from fat redistribution, it’s worth ruling that out too — our guide on telling if your dog is overweight walks through the difference.