Cushing's Disease: Why Diagnosis Is Hard, and What Treatment Can Do
Drinking more, eating more, panting and a pot belly in an older dog can be Cushing's. Why no test is perfect, and what treatment aims to do.
Written by thecanineledger
The 2012 consensus statement on diagnosing Cushing’s disease in dogs, written for the American College of Veterinary Internal Medicine, is blunt: “None of the biochemical screening or differentiating tests for hyperadrenocorticism are perfect” (Behrend et al., Journal of Veterinary Internal Medicine 2013, abstract).
It adds a second warning: “Endocrine tests should be performed only when clinical signs consistent with HAC are present.” HAC is hyperadrenocorticism, the formal name for Cushing’s.
While a blood test result seems definitive, with Cushing’s it isn’t. Testing a dog without the signs can mislead. This page explains what Cushing’s is, why diagnosis takes more than one test, and what treatment aims to do.
1. What it is, and its new name
Cushing’s happens when the body is exposed to too much cortisol, a stress hormone, for a long time.
The cause. The Merck Veterinary Manual’s owner page explains that “The most common cause (85% to 90% of cases) is a tumor in the pituitary gland.” That tumour, in the brain, drives the adrenal glands to overproduce. “Less common (10% to 15% of cases) is a tumor in the adrenal glands themselves.” Long-term steroid medication can cause the same signs (Merck, Disorders of the Adrenal Glands in Dogs).
The name. In 2025, a panel of experts from the European Society of Veterinary Endocrinology and the Society of Comparative Endocrinology agreed new definitions. “ALIVE discourages the use of the term Cushing’s disease or hyperadrenocorticism for the umbrella term of this clinical syndrome.” The preferred term is Cushing’s syndrome (Niessen et al., Veterinary Sciences 2025). Your vet may use any of these names.
2. Which dogs get it
A study of 905,544 dogs at UK primary-care practices put the one-year prevalence at 0.17% (Schofield et al., Journal of Small Animal Practice 2022).
Breeds. The Bichon Frise (about 6 times the odds of crossbreeds), Border Terrier (about 5 times) and Miniature Schnauzer (about 3 times) “had the highest odds of Cushing’s syndrome.” Golden and Labrador Retrievers “were the most protected breeds.”
Other factors. “Increasing age, bodyweight greater than the breed‐sex mean and being insured also showed increased odds”. The insurance link probably reflects which dogs get tested, not which dogs get ill.
Our note: The insurance explanation is ours. The study doesn’t give one. We rounded the breed odds ratios (6.17, 5.40, 3.05).
→ Choosing a Breed or a Mix: The Health Data Breeders Don’t Lead With
3. The signs
The 2025 expert panel created a clinical score that vets can use to track a dog with Cushing’s. Its five headings show what owners notice:
- Drinking, from “some increase in drinking” to “constantly seen to be drinking”
- Urination, up to “constantly needs to be let out to urinate”
- Appetite, from “finishes eagerly” to “obsessed with food”
- Appearance, from “slightly poor hair and skin quality” to “substantial hair loss and/or noticeable muscle loss/pot belly”
- Attitude and activity, including “panting more than normal”
The changes are slow, and in an older dog they are easy to put down to age.
→ Is It Old Age, or Something Treatable? A Guide to Your Senior Dog
4. Why diagnosis is hard
No perfect test. The 2012 consensus says none of the screening tests is perfect, so your vet may need more than one.
Test only when there are signs. Other illnesses raise cortisol too. A dog tested without the typical signs is more likely to get a misleading result.
Signs, but normal tests. The 2025 panel defines “Subdiagnostic Cushing’s Syndrome”: a dog that “appears to have Cushing’s syndrome, yet the results of dynamic testing of pituitary-adrenal function fall into appropriate (normal) reference intervals.”
Telling the causes apart. Your vet may recommend further tests or a scan to find out whether the problem is in the pituitary or an adrenal gland. The panel says that “Differentiating between forms of naturally occurring Cushing’s syndrome is highly desirable in order to optimise management strategies and prognosticate.”
Our note: “Other illnesses raise cortisol too” is our explanation of why the consensus says to test only dogs with signs.
5. What treatment aims to do
The aim is to control the signs. The 2025 panel’s clinical score sets the “Treatment aim: lowest score possible without unacceptably high risk of hypoadrenocorticism.” Hypoadrenocorticism is Addison’s disease, where cortisol is too low. Treatment walks a line between the two.
Steroid-induced Cushing’s. When the cause is steroid medication, the panel says it “is treated by gradual cessation of exogenous glucocorticoid administration.” Never stop a steroid suddenly without your vet.
Monitoring. Your vet will recheck your dog’s signs and blood tests, and adjust treatment.
Buying medication online. Cushing’s medication needs regular testing to be used safely. Don’t buy it without a prescription and a monitoring plan.
Our note: We don’t cover surgery, radiotherapy or medicines here, because we haven’t read a source we’d want to quote on them.
Our note: The paragraph on buying medicine online is ours.
→ Addison’s Disease: The Great Pretender · → Diabetes in Dogs: Insulin, Home Monitoring, and Glucose Sensors · → Buying Your Dog’s Medicines Online, Safely
6. What we could not verify
| Commonly said | What we found |
|---|---|
| “One blood test will confirm it” | No. The 2012 consensus says no screening test is perfect. |
| “Every older dog should be screened” | No. The consensus says test only dogs with consistent signs. |
| “Treatment cures it” | We found no source we read on cure rates. The 2025 panel frames the aim as controlling the signs while avoiding Addison’s. |
| “Retrievers are prone to it” | The opposite in the UK study. Golden and Labrador Retrievers had the lowest odds. |
| “Normal tests rule it out” | Not always. Experts now define a subdiagnostic form with normal test results. |
Sources
- Behrend EN, Kooistra HS, Nelson R, Reusch CE, Scott-Moncrieff JC. Diagnosis of spontaneous canine hyperadrenocorticism: 2012 ACVIM consensus statement (small animal). J Vet Intern Med 2013. ⚠️ abstract read. Consensus statement
- Niessen SJM, Behrend EN, Fracassi F, et al. Agreeing Language in Veterinary Endocrinology (ALIVE): Cushing’s Syndrome and Hypoadrenocorticism: A Modified Delphi-Method-Based System to Create Consensus Definitions. Vet Sci 2025: expert consensus on definitions
- Schofield I, Brodbelt DC, Niessen SJM, et al. Frequency and risk factors for naturally occurring Cushing’s syndrome in dogs attending UK primary-care practices. J Small Anim Pract 2022: VetCompass, 905,544 dogs
- Merck Veterinary Manual: Disorders of the Adrenal Glands in Dogs (pet owner version; Bruyette, DACVIM; full review Jun 2018, last updated May 2026)
Always confirm with your vet before acting on anything on this page.