The first signs of Cushing’s disease in dogs are usually increased thirst, increased urination, and increased appetite. These three changes tend to appear together and gradually worsen over weeks to months, making them easy to dismiss as normal aging. But when a dog that never begged for food suddenly acts starving, or a housetrained dog starts having accidents overnight, Cushing’s disease belongs on the list of possible causes.
The Three Earliest and Most Common Signs
Excess cortisol, the stress hormone at the root of Cushing’s disease, disrupts how your dog’s body handles water and hunger signals. That produces a predictable trio of early symptoms: drinking more water, urinating more frequently, and acting ravenous even right after meals.
A healthy dog drinks roughly 40 to 60 milliliters of water per kilogram of body weight each day. For a 30-pound (roughly 14 kg) dog, that works out to about two to three cups. A dog is considered abnormally thirsty once intake exceeds 100 milliliters per kilogram, which would be more than double the normal amount. In practical terms, you might notice the water bowl emptying faster than usual, your dog seeking out unusual water sources like toilet bowls or puddles, or needing to go outside far more often. Many owners first suspect a problem when their previously housetrained dog begins urinating indoors overnight.
The increased appetite can be dramatic. Dogs with early Cushing’s may guard food, counter-surf, beg persistently, or eat things they normally wouldn’t touch. This happens because cortisol directly stimulates appetite centers in the brain, creating a feeling of constant hunger regardless of how much your dog has eaten.
Skin and Coat Changes
Hair loss is one of the most visible early signs, and it follows a distinctive pattern. The fur thins symmetrically on both sides of the body, typically along the flanks, belly, and sides of the chest. The head and legs are usually spared. Unlike hair loss from allergies or infections, the skin underneath isn’t usually itchy. Instead, it may look thin, dry, or fragile, and you might notice small blackheads forming on the belly.
Some dogs develop patches of darkened skin or bruise more easily than before. Wounds and minor cuts may heal slowly. These skin changes happen because cortisol breaks down collagen and suppresses the normal turnover of skin cells.
The Pot-Bellied Look
A sagging, rounded belly is one of the most recognizable physical changes in dogs with Cushing’s disease, and it can develop relatively early. Two things cause it: cortisol weakens the abdominal muscles, making them less able to hold everything in place, and the liver enlarges as it processes the excess hormone. The combination gives your dog a potbellied appearance even if they haven’t gained significant weight elsewhere. If your dog’s belly seems to hang lower than it used to, especially alongside increased thirst or appetite, that’s a meaningful clue.
Panting, Lethargy, and Muscle Weakness
Dogs with early Cushing’s often pant excessively, even at rest or in cool temperatures. This is partly because the enlarged liver and redistributed abdominal fat put pressure on the diaphragm, and partly because cortisol affects the respiratory centers directly. Owners sometimes describe their dog as “always out of breath” despite not exercising more than usual.
Muscle weakness and reduced activity tend to creep in gradually. Your dog may struggle with stairs, hesitate before jumping onto furniture, or seem less interested in walks. These changes are easy to chalk up to aging, especially since Cushing’s most commonly affects middle-aged and older dogs. But when reduced energy appears alongside increased thirst or a changing body shape, the combination points toward something more specific than age alone.
Recurring Infections
Cortisol suppresses the immune system, which means dogs with Cushing’s are prone to infections their bodies would normally fight off. Urinary tract infections are especially common and can be “silent,” meaning your dog may not show obvious signs of pain or straining. The only clue might be that the increased urination seems to worsen, or that a urine test at the vet comes back positive for bacteria. Skin infections that keep returning despite treatment are another early red flag.
Why These Signs Are Easy to Miss
Cushing’s disease develops slowly. The symptoms don’t appear all at once, and individually, each one has a long list of other possible explanations. A dog drinking more water could be reacting to warmer weather. Hair thinning could be seasonal. A bigger appetite could just mean your dog likes the new food. What makes Cushing’s distinct is the clustering of these signs together and their gradual, steady progression over months.
The disease is caused by the body producing too much cortisol, most often because of a small, benign tumor on the pituitary gland at the base of the brain. Less commonly, a tumor on one of the adrenal glands (which sit near the kidneys) is responsible. In both cases, the result is the same: a chronic flood of cortisol that affects nearly every organ system.
How Cushing’s Is Diagnosed
No single test confirms Cushing’s on its own. Vets typically start with blood work and a urinalysis, looking for patterns like elevated liver enzymes and dilute urine. If Cushing’s is suspected, two specialized hormone tests are used most often.
The first is a low-dose dexamethasone suppression test, which is better at ruling the disease out. If this test comes back normal, Cushing’s is unlikely. The second is an ACTH stimulation test, which is better at ruling the disease in. A positive result on this test is strong evidence that Cushing’s is present. Your vet may use one or both depending on how clear the clinical picture is. Abdominal ultrasound can also help by revealing an enlarged liver or changes to the adrenal glands.
What to Watch For at Home
If you suspect early Cushing’s, tracking a few things at home can help your vet enormously. Measure how much water your dog drinks over a 24-hour period by filling the bowl to a marked level and checking what’s left. Note how many times your dog needs to go outside to urinate, and whether accidents have started happening. Take photos of any thinning fur or changes to your dog’s body shape over time.
Cushing’s is most common in dogs over six years old. Breeds with higher rates include Poodles, Dachshunds, Boston Terriers, Boxers, and Beagles, though any breed can be affected. If your older dog is showing two or more of these signs, especially the thirst-urination-appetite combination alongside skin or body shape changes, a vet visit with hormone testing is the logical next step.