What Cushing’s Disease Is and How to Recognize It in Dogs
Cushing’s disease — known medically as hyperadrenocorticism (an overactive adrenal gland response) — is a condition in which a dog’s body is exposed to too much cortisol, the main stress hormone. Cortisol is normally helpful in small amounts, but a chronic excess slowly affects nearly every organ system. Per the Merck Veterinary Manual, the most common signs in dogs include polyuria and polydipsia (increased urination and thirst), polyphagia (a noticeably bigger appetite), a pendulous or “pot-bellied” abdomen, panting, muscle wasting, and skin changes such as hair loss, recurrent skin infections, and thin skin. Owners often first notice a previously house-trained dog asking to go out more, draining the water bowl, or begging constantly for food.
The skin and coat changes are especially telling. The hair loss is typically bilaterally symmetric — thinning evenly on both flanks rather than in random patches — and the skin may feel thin or fragile and bruise easily. According to VCA Animal Hospitals, affected dogs frequently develop persistent bladder infections, chronic skin or ear infections, and poor wound healing because excess cortisol suppresses the immune system. Many also pant heavily even at rest and tire quickly due to muscle weakness. No single sign confirms the disease, and several mimic ordinary aging, but the combination of more drinking, more urinating, more eating, and a sagging belly in a middle-aged or older dog is the classic pattern that should prompt a veterinary visit rather than watchful waiting.
What Causes Cushing’s Disease (Hyperadrenocorticism)
Cushing’s comes in three forms. The most common is pituitary-dependent hyperadrenocorticism, in which a small tumor on the pituitary gland (a hormone-control gland at the base of the brain) overproduces a signal called ACTH, driving the adrenal glands to flood the body with cortisol. Per the Merck Veterinary Manual, this pituitary form accounts for roughly 80–85% of cases — the large majority. The second form is adrenal-dependent disease, caused by a tumor on one of the adrenal glands themselves; Merck notes this accounts for about 10–15% of cases. Both forms produce identical outward signs, because the underlying problem — too much circulating cortisol — is the same regardless of where it originates.
The third form is iatrogenic Cushing’s, meaning “caused by treatment.” According to VCA Animal Hospitals, it develops when a dog receives oral or injectable corticosteroids (steroid medications) over a long period, often for allergies or immune conditions, and the body responds as if cortisol were genuinely in excess. This form is important because it is largely preventable and frequently reversible. Regarding who is affected, the Merck Veterinary Manual reports that Cushing’s occurs in middle-aged to older dogs — commonly around 7 to 12 years — and can affect any breed or size, though pituitary cases are reported more often in smaller breeds such as Miniature Poodles, Dachshunds, and Yorkshire Terriers, while adrenal tumors tend to occur somewhat more often in larger dogs.
Diagnosis and When to See a Vet
Cushing’s cannot be diagnosed from symptoms alone, and it genuinely needs veterinary diagnosis — this is not a condition to self-treat or wait out. There is no single perfect test. A veterinarian usually starts with a history, physical exam, routine bloodwork, and urinalysis, then runs a screening hormone test. Per the Merck Veterinary Manual, the low-dose dexamethasone suppression test (LDDST) is the screening test of choice, and the ACTH stimulation test is another commonly used screening test. The urine cortisol:creatinine ratio is a sensitive screening test most useful for helping rule out the disease, since a normal result makes Cushing’s unlikely. Because each test has limitations, vets often interpret results together with the clinical picture.
Once the diagnosis is confirmed, further testing pins down which form is present, since that determines treatment. Per the Merck Veterinary Manual, abdominal imaging — ultrasound or CT — is an important part of the workup and helps distinguish a pituitary cause from an adrenal tumor, and measuring endogenous ACTH can help differentiate the two. For suspected iatrogenic cases, VCA Animal Hospitals notes the diagnosis is supported when a dog on steroid medication shows little or no response to an ACTH stimulation test. You should book a veterinary appointment if your dog is drinking and urinating noticeably more, eating ravenously, losing coat symmetrically, or developing a pot-bellied appearance — especially since these signs can overlap with diabetes and other serious conditions that also require prompt diagnosis.
The Diet Connection: Feeding a Dog with Cushing’s
Let’s be clear up front: no food cures or treats Cushing’s disease. Medication or surgery addresses the cortisol excess; diet plays only a supportive role in keeping a dog comfortable and managing complications. That said, nutrition matters because chronic cortisol excess drives muscle wasting, so a diet built around adequate, high-quality, easily digestible protein helps counter muscle loss and supports body condition — always within whatever guidance your veterinarian sets. If you want a structured starting point for products that fit these goals, see our Best Dog Food for Cushing’s Disease guide, but treat any food choice as a complement to medical care, never a replacement for it.
Fat deserves attention too. Per the MSD Veterinary Manual, hyperadrenocorticism is a recognized risk factor for pancreatitis in dogs, and because pancreatitis is triggered and worsened by dietary fat, a moderate or controlled-fat diet is a sensible precaution — MSD notes that dogs needing pancreatitis management are generally fed a low-fat ration of less than 20 grams of fat per 1,000 kcal. The other major dietary issue is concurrent diabetes: the Merck Veterinary Manual reports that roughly 10% of dogs with hyperadrenocorticism also have diabetes mellitus. If your dog has both, blood-sugar-friendly feeding becomes a priority; our Best Dog Food for Diabetes guide covers that overlap. Have your veterinarian confirm the right protein, fat, and calorie targets for your individual dog.
Managing Cushing’s Disease and What to Avoid
For the two naturally occurring forms, treatment is lifelong management rather than a one-time fix. Per the Merck Veterinary Manual, most dogs are treated medically with trilostane or mitotane — medications that reduce the adrenal glands’ cortisol output — while an adrenal tumor may be addressed surgically by removing the affected gland. VCA Animal Hospitals notes that medical treatment cannot truly cure pituitary Cushing’s, but good control is often possible for years. These medications require veterinary monitoring with periodic recheck tests, because dosing must be adjusted carefully; giving too much can swing a dog toward dangerously low cortisol. The iatrogenic form is managed differently, by gradually tapering off the steroid under veterinary supervision — never stopping steroids abruptly on your own.
What to avoid: do not attempt to manage suspected Cushing’s with over-the-counter “adrenal support” supplements or diet changes in place of diagnosis and medication, and do not ignore the early signs as simply old age. Because Cushing’s can coexist with diabetes and raises pancreatitis risk per the MSD and Merck Veterinary Manuals, watch for vomiting, appetite loss, or sudden lethargy and report them promptly, as they can signal a complication. Keep all recheck appointments, give medications exactly as prescribed and with food when directed, and loop your veterinarian into any food changes. Managed well, many dogs with Cushing’s live comfortable lives — but the disease is controlled, not cured, and steady veterinary partnership is what makes that possible.
Frequently asked questions
Is Cushing’s disease in dogs fatal, and how long can a dog live with it?
Cushing’s is a serious but generally manageable condition, not an immediate death sentence. With proper treatment, many dogs live comfortably for years. According to VCA Animal Hospitals, medical treatment cannot cure a dog with pituitary-dependent Cushing’s disease, but control is possible for many years if the tumor is small. Outcomes depend on the form, the dog’s age, how early it’s caught, and whether complications like diabetes or pancreatitis develop. The key is an accurate veterinary diagnosis, the right medication (commonly trilostane or mitotane), and consistent monitoring with recheck tests, since untreated disease tends to worsen quality of life over time (per the Merck Veterinary Manual).
Can a special diet cure or treat my dog’s Cushing’s disease?
No. There is no food, supplement, or diet that cures or treats Cushing’s disease — the cortisol excess is corrected with medication or surgery, not nutrition. Diet plays only a supportive role. Because excess cortisol causes muscle wasting, a diet with adequate high-quality protein can help maintain muscle, and because Cushing’s raises pancreatitis risk, a moderate, controlled-fat diet is often sensible. If your dog also has diabetes, blood-sugar management becomes important too. Always set protein, fat, and calorie targets with your veterinarian rather than relying on marketing claims, and treat any food as a complement to medical treatment, never a replacement (per the MSD and Merck Veterinary Manuals).
What are the first signs of Cushing’s disease in dogs that owners usually notice?
The earliest changes owners typically spot are increased thirst, increased urination, and a bigger appetite. Per the Merck Veterinary Manual, the most common signs include polyuria and polydipsia (more urinating and drinking), polyphagia (increased appetite), a pendulous “pot-bellied” abdomen, panting, muscle wasting, and skin changes such as symmetric hair loss and thin skin. A dog that suddenly drains the water bowl, asks to go outside far more often, begs constantly for food, or develops a sagging belly — especially a middle-aged or older dog — should be evaluated by a veterinarian, since these signs overlap with diabetes and other conditions that need prompt diagnosis (per the Merck Veterinary Manual).
For diet-side context, see Best Dog Food for Cushing’s Disease, Best Dog Food for Diabetes. To check whether your dog’s food matches the rubric criteria discussed above, paste the ingredient list into the KibbleIQ analyzer. For scoring methodology context, see our published methodology.
Related condition deep-dives: Addison’s Disease in Dogs · Hypothyroidism in Dogs.