Symptoms, Diagnosis & Treatment Guide

What Is Cushing's Disease in Dogs?

Cushing's disease, medically known as hyperadrenocorticism (HAC), is an endocrine disorder caused by prolonged overproduction of cortisol — the body's primary stress hormone. In healthy dogs, cortisol is tightly regulated by the pituitary-adrenal axis. When this system breaks down, excess cortisol floods the body, triggering a cascade of metabolic, immune, and dermatological changes that can significantly impact quality of life.

There are three recognized forms of Cushing's disease:

• Pituitary-dependent hyperadrenocorticism (PDH): Accounts for approximately 80–85% of cases. A benign tumor (adenoma) on the pituitary gland overproduces ACTH, which stimulates the adrenal glands to release excess cortisol.
• Adrenal-dependent hyperadrenocorticism (ADH): Represents roughly 15–20% of cases. A tumor on one of the adrenal glands directly secretes cortisol independent of pituitary signaling. About 50% of adrenal tumors are malignant (adenocarcinomas).
• Iatrogenic Cushing's syndrome: Caused by prolonged administration of corticosteroid medications (prednisone, dexamethasone, methylprednisolone) used to treat allergies, autoimmune conditions, or inflammation.

According to the Merck Veterinary Manual, Cushing's disease is one of the most commonly diagnosed endocrine disorders in dogs, affecting an estimated 1 to 2 out of every 1,000 dogs annually. It predominantly strikes middle-aged to older dogs, typically between 7 and 12 years of age.

Recognizing the Signs of Cushing's Disease in Dogs

One of the most challenging aspects of Cushing's disease is its insidious onset. Symptoms develop gradually over months or even years, and many owners dismiss early changes as normal aging. Understanding the progression from subtle early indicators to advanced clinical signs is critical for timely veterinary intervention.

Early Warning Signs (Often Overlooked)

These symptoms typically appear first and may be present for 6–12 months before a diagnosis is made:

Advanced Clinical Signs

As the disease progresses untreated, more visible and systemic symptoms emerge:

How Is Cushing's Disease Diagnosed in Dogs?

Diagnosing Cushing's disease is among the more complex endocrine workups in veterinary medicine. No single test is 100% definitive, and veterinarians typically use a staged approach combining clinical suspicion with sequential laboratory testing. According to the American College of Veterinary Internal Medicine (ACVIM) consensus statements, diagnosis requires both compatible clinical signs AND confirmatory laboratory results.

Step-by-Step Diagnostic Process

1. Initial Screening — Complete Blood Count (CBC) and Serum Biochemistry Panel
   Your vet will first run baseline blood work. Findings suggestive of Cushing's include: elevated alkaline phosphatase (ALP) — seen in over 90% of cases, elevated ALT, stress leukogram (elevated neutrophils, low lymphocytes and eosinophils), hypercholesterolemia, and hyperglycemia. Dilute urine (urine specific gravity below 1.020) on urinalysis is also a hallmark. Estimated cost: $150–$300.
2. Urine Cortisol:Creatinine Ratio (UCCR)
   A first-morning urine sample collected at home (to avoid stress-induced cortisol elevation from the clinic visit). A normal UCCR effectively rules out Cushing's (high sensitivity), but an elevated result is not specific — stress, illness, and other conditions can raise it. This is a screening test, not a confirmatory one. Estimated cost: $50–$100.
3. Low-Dose Dexamethasone Suppression Test (LDDST)
   Considered the gold-standard screening test for PDH. A small dose of dexamethasone (0.01 mg/kg IV) is administered, and blood cortisol levels are measured at 0, 4, and 8 hours. In healthy dogs, dexamethasone suppresses cortisol production. In Cushing's dogs, suppression fails. The LDDST can also help differentiate PDH from ADH in some cases (if cortisol suppresses at 4 hours but escapes at 8 hours, PDH is likely). Estimated cost: $200–$350.
4. ACTH Stimulation Test
   Synthetic ACTH (cosyntropin, 5 µg/kg IV or IM) is administered, and cortisol is measured before and 1 hour after injection. This test has high specificity for Cushing's but lower sensitivity (approximately 60–65% for PDH, higher for ADH). It is the preferred test when iatrogenic Cushing's is suspected and is essential before starting treatment with mitotane or trilostane to establish a baseline. Estimated cost: $150–$275 (cosyntropin costs have risen significantly in recent years).
5. High-Dose Dexamethasone Suppression Test (HDDST)
   Used to differentiate PDH from ADH after a Cushing's diagnosis is confirmed. A higher dexamethasone dose (0.1 mg/kg IV) is given, and cortisol is measured at 0, 4, and 8 hours. PDH tumors may still partially suppress at this dose, while adrenal tumors will not. However, this test has been partially supplanted by endogenous ACTH measurement and imaging. Estimated cost: $200–$350.
6. Endogenous ACTH (eACTH) Concentration
   A direct blood measurement of ACTH levels. High or normal eACTH indicates PDH (the pituitary is driving the process); low or undetectable eACTH indicates ADH (the adrenal tumor is producing cortisol independently, suppressing pituitary ACTH via negative feedback). Sample handling is critical — blood must be collected in a chilled EDTA tube, processed immediately, and frozen for shipping. Estimated cost: $100–$200.
7. Abdominal Ultrasound
   Directly visualizes the adrenal glands. In PDH, both adrenals are typically normal to mildly enlarged. In ADH, one adrenal gland is enlarged (often with a mass) while the contralateral gland is atrophied (shrunken due to ACTH suppression). Ultrasound also screens for liver enlargement, urinary calculi, and possible metastatic disease. Estimated cost: $300–$600 depending on region and specialist involvement.
8. Advanced Imaging (CT or MRI)
   Recommended when a pituitary macroadenoma (tumor >10 mm) is suspected based on neurological signs (head pressing, disorientation, visual deficits, seizures) or when surgical planning for adrenalectomy is needed. CT of the abdomen provides detailed adrenal and vascular anatomy; MRI of the brain evaluates pituitary tumor size. Estimated cost: $800–$2,000+ per scan.

Treatment Options for Cushing's Disease in Dogs

Treatment depends on the type of Cushing's (PDH vs. ADH vs. iatrogenic), the dog's overall health, tumor characteristics, and owner budget. The goal is not to "cure" the disease in most cases but to achieve controlled cortisol levels that restore quality of life and prevent complications.

Monitoring During Treatment

Regardless of which medication is used, rigorous monitoring is essential to avoid both under-treatment (persistent Cushing's symptoms) and over-treatment (iatrogenic Addison's disease — an acute, potentially life-threatening cortisol deficiency).

Typical monitoring schedule for trilostane or mitotane:

• ACTH stimulation test at 10–14 days after starting treatment
• Repeat ACTH stim at 30 days, then at 90 days
• Once stable: ACTH stim and biochemistry panel every 3–6 months for life
• Blood pressure monitoring at each visit (hypertension is a common comorbidity)
• Owner monitoring of water intake, appetite, energy level, and urination frequency daily at home

⚠️ Never adjust your dog's trilostane or mitotane dose without veterinary guidance. Over-treatment can cause acute hypoadrenocorticism (Addisonian crisis), which presents as vomiting, diarrhea, collapse, and shock — a true medical emergency.

Prognosis and Life Expectancy for Dogs with Cushing's Disease

The prognosis for Cushing's disease varies considerably based on the underlying cause, whether treatment is pursued, tumor characteristics, and the presence of complications such as diabetes mellitus, hypertension, or pulmonary thromboembolism.

It's important to note that many dogs with well-managed PDH die from unrelated causes (cancer, kidney failure, cardiac disease) rather than from Cushing's itself. The disease is serious but, when caught and managed appropriately, is very compatible with years of good-quality life.

Home Care and Daily Management

Living with a Cushing's dog requires consistent daily routines and vigilant observation. Here's what a typical management plan looks like in practice:

Medication Administration

• Trilostane should be given with food (improves absorption) — ideally a meal containing some fat. Most dogs require twice-daily dosing for optimal cortisol control, though some protocols start with once daily.
• Administer doses at consistent 12-hour intervals (e.g., 7 AM and 7 PM) to maintain stable cortisol suppression.
• Keep a medication log — note any missed doses, GI upset, or behavioral changes.
• Never double a missed dose. If you miss a dose and the next one is due within 4 hours, skip it.

Monitoring at Home

• Water intake: Measure daily water consumption. A useful benchmark: normal is approximately 40–60 mL per kg of body weight per day. A 10 kg (22 lb) dog should drink roughly 400–600 mL (about 2–2.5 cups) daily. Consistent intake above 100 mL/kg/day warrants a vet check.
• Appetite: Note whether ravenous hunger is normalizing with treatment. Persistent excessive appetite may indicate under-dosing.
• Activity level: Track willingness to walk, climb stairs, and play. Improving energy is a positive treatment indicator.
• Coat and skin: Hair regrowth is slow — expect 3–6 months before visible improvement. Photograph affected areas monthly to track progress objectively.
• Urine output: Monitor frequency and volume. Sudden changes may indicate UTI (very common in Cushing's dogs due to immunosuppression and dilute urine).

Diet and Lifestyle Adjustments

• Feed a high-quality, AAFCO-approved diet appropriate for your dog's life stage. Moderate protein, moderate fat, and controlled sodium are generally recommended — particularly if hypertension or kidney concerns exist.
• Avoid high-fat treats and table scraps, as Cushing's dogs are predisposed to pancreatitis and hyperlipidemia.
• Maintain a healthy body condition score (BCS 4–5 on a 9-point scale). Weight management reduces stress on weakened abdominal muscles and joints.
• Provide easy access to fresh water at all times — never restrict water intake, even if urination is excessive. Restricting water in a polyuric dog can lead to dangerous dehydration.
• Gentle, regular exercise (short walks, swimming if available) helps maintain muscle tone without overexertion.

Managing Complications

Cushing's dogs are prone to several secondary conditions that require proactive management:

• Urinary tract infections: Up to 50% of Cushing's dogs develop UTIs, often without obvious symptoms (due to immunosuppression masking inflammation). Urinalysis with culture should be performed every 3–6 months even in asymptomatic dogs.
• Hypertension: Blood pressure should be checked at every veterinary visit. Anti-hypertensive medication (amlodipine, telmisartan) may be needed.
• Diabetes mellitus: Approximately 10–15% of Cushing's dogs develop concurrent diabetes. Controlling Cushing's often improves insulin sensitivity, but some dogs require insulin therapy.
• Pulmonary thromboembolism (PTE): A serious and potentially fatal complication. Cushing's creates a hypercoagulable state. Signs include sudden respiratory distress, rapid breathing, and collapse — this is an emergency.
• Gallbladder mucocele: More common in Cushing's dogs; detected on ultrasound. May require surgical intervention if causing obstruction or rupture risk.

The Cost of Cushing's Disease Treatment

Cushing's disease is a chronic condition requiring lifelong investment. Understanding the full financial picture helps owners plan realistically and avoid lapses in care.

Cost Breakdown

First-year total cost estimate (medical management of PDH): $2,000–$5,000 depending on diagnostic complexity and geographic location.

Ongoing annual cost (stable, uncomplicated case): $1,200–$3,000 per year for medication and monitoring.

Worst-case scenario (surgery, radiation, or severe complications): $8,000–$15,000+ in the first year.

Pet insurance can be valuable here — if enrolled before diagnosis, many plans cover diagnostic testing, medications, and surgery. However, Cushing's diagnosed before enrollment will be excluded as a pre-existing condition. Review policy terms for endocrine disease coverage and annual/lifetime limits carefully.

When to See the Vet Immediately

For non-emergency situations, schedule a veterinary appointment promptly if you notice:

• Gradual increase in thirst and urination over several weeks
• New or worsening hair loss, particularly symmetrical on the trunk
• Progressive abdominal enlargement
• Recurrent skin or ear infections that don't resolve with standard treatment
• Changes in appetite or energy level in a middle-aged or senior dog

Important: This guide is intended for educational purposes. Only a licensed veterinarian can diagnose Cushing's disease and prescribe appropriate treatment. Always consult your veterinarian before making any changes to your dog's medication, diet, or care plan.

Frequently Asked Questions

Can Cushing's disease in dogs be cured?

In most cases, Cushing's disease is managed rather than cured. Pituitary-dependent Cushing's (80–85% of cases) requires lifelong medication because the pituitary tumor cannot typically be removed. Adrenal-dependent Cushing's caused by a benign adenoma can be cured through surgical removal of the affected adrenal gland, provided there is no metastasis. Iatrogenic Cushing's is fully reversible once exogenous steroids are tapered under veterinary supervision.

Which dog breeds are most prone to Cushing's disease?

Breeds with documented predisposition include: Poodles (Miniature and Toy varieties especially), Dachshunds, various Terriers (Yorkshire Terrier, Boston Terrier, Staffordshire Bull Terrier), Beagles, German Shepherds, Cocker Spaniels, and Bichon Frises. However, Cushing's can develop in any breed. Small-breed dogs are generally overrepresented for PDH, while larger breeds have a relatively higher proportion of adrenal tumors.

How long can a dog live with untreated Cushing's disease?

Untreated Cushing's disease is not immediately fatal, but it progressively degrades quality of life and increases the risk of life-threatening complications. Without treatment, median survival is estimated at 1–2 years, though some dogs survive longer. The primary risks of untreated disease include pulmonary thromboembolism (blood clots in the lungs), severe infections due to immunosuppression, congestive heart failure, pancreatitis, diabetes mellitus, and neurological deterioration from expanding pituitary tumors.

Is Cushing's disease painful for dogs?

Cushing's disease itself is not typically painful in the way that arthritis or dental disease is. However, it causes significant discomfort through muscle weakness, skin infections, chronic hunger, and restlessness. Complications such as pancreatitis, UTIs, calcinosis cutis (calcium deposits in the skin), and gallbladder mucoceles can be painful. Most owners report a noticeable improvement in their dog's demeanor and comfort within 2–4 weeks of starting effective treatment.

Can diet alone treat Cushing's disease?

No. There is no diet, supplement, or natural remedy that can treat or reverse Cushing's disease. While proper nutrition supports overall health and helps manage secondary issues like hyperlipidemia and obesity, the underlying hormonal imbalance requires medical or surgical intervention. Be cautious of online claims suggesting that herbal supplements, melatonin, or lignans can replace prescribed medication — while some supplements may have mild supportive effects on coat quality, they do not address cortisol overproduction. Always discuss any supplement with your veterinarian before adding it to your dog's regimen.

What happens if I miss giving my dog's trilostane dose?

Missing a single dose is generally not dangerous. Administer the next dose at the regular scheduled time — do not double the dose to "make up" for the missed one. Cortisol levels will temporarily rise, and you may notice a brief increase in thirst or appetite, but this typically resolves with the next dose. If you miss multiple consecutive doses (e.g., over a weekend), contact your veterinarian for guidance on whether a recheck ACTH stimulation test is needed before resuming.

Are there any new treatments for Cushing's disease in dogs?

Research into Cushing's disease management is ongoing. Recent areas of investigation include: osilodrostat (a newer 11β-hydroxylase inhibitor used in human Cushing's, being studied for veterinary use), improved stereotactic radiation protocols for pituitary macroadenomas, and laparoscopic adrenalectomy techniques that reduce surgical morbidity. Consultation with a veterinary internal medicine specialist (DACVIM) is recommended for dogs with complex or refractory cases to access the most current treatment options.