Cushing’s disease in dogs doesn’t have three formally defined clinical stages in veterinary medicine. Unlike cancer staging, there’s no standardized system that classifies Cushing’s into stage 1, 2, or 3. What veterinarians and pet owners do recognize, however, is a clear pattern of progression: early subtle signs, visible physical changes, and eventually serious complications. Understanding this progression helps you catch the disease sooner and know what to expect as it advances.
Why You’ll See “Three Stages” Online
Many pet health sources describe Cushing’s in three phases because the disease does follow a recognizable arc. Early symptoms are easy to dismiss as normal aging. Middle symptoms become hard to ignore. Late symptoms involve organ damage and secondary diseases. This framework is useful for dog owners trying to figure out where their pet falls on the spectrum, even though your vet won’t use formal staging language the way an oncologist would.
Cushing’s disease occurs when a dog’s body produces too much cortisol, the stress hormone. In roughly 80 to 85 percent of cases, the cause is a small tumor on the pituitary gland at the base of the brain. The remaining cases come from a tumor on one of the adrenal glands, which sit near the kidneys. Both types produce the same excess cortisol and follow a similar progression of symptoms.
Early Signs: Increased Thirst, Hunger, and Urination
The first signs of Cushing’s are behavioral, not physical, which is why they’re so often missed. Increased drinking and increased urination appear in 80 to 90 percent of cases and are usually the earliest clue. Your dog may suddenly drain the water bowl twice a day, need to go outside more often, or start having accidents in the house overnight. Appetite also ramps up noticeably. Some dogs become pushy about food, beg constantly, or raid the trash.
These changes happen gradually over weeks to months. Many owners chalk them up to aging, especially since Cushing’s typically strikes middle-aged and older dogs. The excess cortisol is already doing internal damage at this point, suppressing the immune system and altering metabolism, but your dog may still look perfectly normal on the outside. This is the window where early diagnosis makes the biggest difference, yet it’s also the phase most likely to be overlooked.
Middle Signs: Physical Changes Become Visible
As cortisol levels stay elevated over months, the disease starts reshaping your dog’s body. The most recognizable change is a pot-bellied appearance. This happens because cortisol redistributes fat to the abdomen and weakens the abdominal muscles, letting the belly sag. At the same time, muscles in the legs and along the spine begin to waste away, making your dog look top-heavy or oddly proportioned.
Coat and skin changes are also hallmarks of this middle phase. Dogs lose hair symmetrically on both sides of the body, often starting on the flanks and trunk while sparing the head and legs. The remaining coat may feel thin and dry. The skin underneath becomes fragile, bruises easily, and heals slowly from even minor wounds. Some dogs develop dark patches of skin or hard, chalky calcium deposits under the skin, a condition called calcinosis cutis that can be painful and prone to infection.
Panting becomes more frequent, even at rest and in cool environments. Dogs may seem restless at night, pace more, or show other behavior changes. Energy levels drop. What once looked like a healthy older dog now looks visibly unwell, and this is typically when most owners bring their concerns to a vet.
Advanced Signs: Secondary Diseases and Complications
Left untreated, the sustained immune suppression from excess cortisol opens the door to serious secondary problems. Recurrent urinary tract infections and skin infections are common because the body can no longer fight off bacteria effectively. Some dogs cycle through rounds of antibiotics without anyone realizing Cushing’s is the underlying cause.
High blood pressure develops in many dogs with advanced Cushing’s and can damage the kidneys, eyes, and heart over time. Diabetes is another significant risk. The constant flood of cortisol interferes with insulin function, and some dogs become permanently diabetic even after Cushing’s is treated. Blood clots are a less common but dangerous complication that can be life-threatening.
In pituitary-dependent cases, the tumor itself can also become a problem. While most pituitary tumors are small and slow-growing, some enlarge enough to press on surrounding brain tissue. This can cause neurological signs like disorientation, circling, vision loss, or seizures. These cases are the most difficult to manage.
How Cushing’s Is Diagnosed
No single test confirms Cushing’s. Your vet will typically start with blood work and a urinalysis, which often show characteristic patterns like elevated liver enzymes and dilute urine. From there, specific hormone tests measure how the adrenal glands respond to stimulation or suppression. An abdominal ultrasound can help determine whether the problem originates from the pituitary or the adrenal glands, which matters for treatment planning.
Diagnosis can take time. False results are common, and vets often need to run more than one type of hormone test before reaching a definitive answer. If your dog is showing the classic combination of increased thirst, a pot belly, and skin changes, that clinical picture carries a lot of weight alongside the lab work.
Treatment and What to Expect
Most dogs with pituitary-dependent Cushing’s are managed with daily oral medication that reduces cortisol production. After starting treatment, your vet will run a hormone response test at 10 to 14 days to check whether the dose is working. Any dose adjustments require another test 10 to 14 days later. Once the right dose is established, monitoring continues at 30 days, 90 days, and then every three months for the rest of your dog’s life.
The good news is that many symptoms are reversible with treatment. Excessive thirst and urination often improve within the first few weeks. The pot belly gradually shrinks as muscle tone returns. Hair regrowth takes longer, sometimes several months, but most dogs do regrow their coat. Energy and behavior typically improve noticeably within the first month or two.
For adrenal tumors, surgery to remove the affected gland can be curative if the tumor hasn’t spread. This is a more involved procedure with higher upfront risk, but it offers the possibility of a complete resolution rather than lifelong medication.
Dogs treated for Cushing’s can live comfortably for years. The disease itself progresses slowly, and with consistent monitoring and dose adjustments, most dogs maintain a good quality of life. The key factor is how early treatment begins and whether secondary complications like diabetes have already taken hold.