How to Check for Cushing’s Disease in Dogs | Vet Tests

Your dog is drinking more than usual, the belly looks a little rounder, and the fur on the flanks seems thinner than it used to be. It’s easy to write these signs off as just part of getting older — many owners do.

The honest answer about checking for Cushing’s disease is that home observation can only raise suspicion; a veterinarian has to run specific blood tests and sometimes imaging to confirm the condition. Here’s what the diagnostic process typically involves and what you can watch for before the vet visit.

What Cushing’s Disease Looks Like in Dogs

Cushing’s disease, also called hyperadrenocorticism, happens when the adrenal glands produce too much cortisol — a hormone that affects nearly every system in the body. According to the Merck Veterinary Manual, it’s considered a common endocrine disorder in dogs.

Most cases are caused by a benign pituitary tumor that signals the adrenals to overproduce cortisol (pituitary-dependent), while a smaller number stem from an adrenal gland tumor itself. Because cortisol affects multiple organs, the signs tend to show up gradually and overlap with those of normal aging or other conditions.

Common Signs to Watch For

Excessive thirst and urination (polydipsia and polyuria) are often the earliest clues. Dogs may also develop a pot-bellied appearance, hair loss on the body that doesn’t grow back, thin and fragile skin that bruises easily, and muscle weakness, especially in the hind legs. If you notice a combination of these changes for more than a few weeks, it’s worth mentioning to your vet.

Why Early Detection Makes a Difference

The signs of Cushing’s disease come on slowly, so many owners don’t realize something is wrong until the symptoms have been present for months. Catching it earlier can help avoid complications like urinary tract infections or skin infections that develop because the immune system is suppressed by high cortisol.

• Polyuria and polydipsia: Drinking and peeing much more than usual — sometimes needing to go out in the middle of the night.
• Hair loss: Losing fur symmetrically on both sides of the body, especially on the flanks and back, without regrowth.
• Thin, fragile skin: Skin that tears easily or shows dark patches (calcinosis cutis) due to calcium deposits.
• Pot-bellied abdomen: A sagging, distended belly that results from weakened abdominal muscles and fat redistribution.
• Muscle weakness and lethargy: Less enthusiasm for walks, trouble jumping into the car, or hind-end trembling.

Not every dog with Cushing’s shows all of these signs, but the more that are present, the stronger the reason to investigate. Your vet will weigh the symptoms against other possible causes before deciding which tests to run.

The Key Diagnostic Tests a Vet Uses

Two main blood tests are used to check for Cushing’s disease in dogs: the low-dose dexamethasone suppression test (LDDST) and the ACTH stimulation test. The FDA outlines the differences in its ACTH vs LDDST overview, noting that both help confirm the diagnosis and can sometimes tell whether the cause is pituitary or adrenal. The LDDST is generally preferred as the initial screening test — the 2023 AAHA guidelines list it as the test of choice.

The LDDST takes about 8 hours: a baseline cortisol level is measured, a low dose of dexamethasone is given intravenously, and blood samples are checked again 8 hours later to see if cortisol has been suppressed. The ACTH stimulation test is faster: a blood sample is taken, synthetic ACTH is injected, and a second blood sample is taken one hour later.

VCA Animal Hospitals point out that while both tests can give false positives, the LDDST tends to be slightly more sensitive for early or mild cases.

Comparing the Two Tests

Your vet will choose the test based on your dog’s symptoms, overall health, and the likelihood of other conditions. Sometimes both tests are run sequentially if the first result is borderline or if the clinical picture is unclear.

What the Full Diagnostic Process Looks Like

Before running the specific Cushing’s tests, your vet will do a thorough physical exam and review your dog’s medical history. Routine blood work (complete blood count and chemistry panel) and a urinalysis are part of the standard workup — they help rule out other illnesses like diabetes or kidney disease that cause similar signs. PetMD notes that this baseline testing is commonly performed to support a diagnosis of Cushing’s disease.

1. Step 1: Identify symptoms and rule out other causes. Your vet will ask about drinking, urination, appetite, and any skin or coat changes. Blood and urine tests help eliminate conditions like diabetes or chronic kidney disease.
2. Step 2: Run the initial screening test (usually LDDST). If the symptoms point toward Cushing’s, the LDDST is performed. The results are interpreted alongside the physical exam findings.
3. Step 3: Confirm with additional testing if needed. If the LDDST suggests Cushing’s, the ACTH stimulation test may be used to confirm and to check adrenal function before starting treatment.
4. Step 4: Consider imaging for further characterization. Abdominal ultrasound or chest X-rays may be recommended to look at adrenal gland size and screen for tumors or other cancers.

Keep in mind that stress or other illnesses can temporarily raise cortisol levels, so your vet may interpret results cautiously and might repeat a test if the first result doesn’t fit the clinical picture.

How Imaging Supports the Diagnosis

Imaging isn’t always necessary, but it can be helpful when blood test results are ambiguous or when your vet suspects an adrenal tumor rather than a pituitary cause. Cornell’s Riney Canine Health Center explains how abdominal ultrasound diagnosis allows the vet to see the size and shape of both adrenal glands — uneven or enlarged glands can point to an adrenal tumor on one side, while symmetrical enlargement suggests pituitary-driven disease.

Chest X-rays may also be ordered if your dog is having trouble breathing or if there’s concern about a tumor that has spread from the adrenals to the lungs. Imaging is typically done after blood tests have already indicated Cushing’s, not as a first step. The risk profile of imaging is very low — ultrasounds are noninvasive and don’t require sedation in most cooperative dogs.

If an adrenal tumor is found, further imaging like CT may be recommended to plan surgical removal. For pituitary-dependent cases, imaging is less common unless neurological symptoms appear.

The Bottom Line

Checking for Cushing’s disease in dogs is a stepwise process that relies on a veterinarian’s expertise — there is no reliable home test. The combination of clinical signs, blood work, and the LDDST or ACTH stimulation test gives the clearest picture. An abdominal ultrasound can add important detail when needed.

If your dog has been drinking more, losing hair, or developing that telltale pot belly, a visit to your veterinarian is the right first step. Your vet can tailor the diagnostic plan to your dog’s individual age, breed, and symptom pattern and guide you through treatment options if Cushing’s is confirmed.