Cushing's Disease (Hyperadrenocorticism) in Dogs — Symptoms, Diagnosis & Treatment

Disclaimer: This article is for informational purposes only and does not substitute for professional veterinary advice. If you suspect your dog has Cushing's disease, consult a licensed veterinarian for proper diagnosis and treatment.

What Is Cushing's Disease (Hyperadrenocorticism)?

Cushing's disease, known medically as hyperadrenocorticism, is a common endocrine (hormonal) disorder in dogs caused by the chronic overproduction of cortisol by the adrenal glands. Cortisol is a steroid hormone essential for regulating metabolism, immune response, and stress, but when produced in excess it causes widespread damage to nearly every organ system. The condition most often affects middle-aged and older dogs and can develop so gradually that early signs are mistaken for normal aging.

The hormonal pathway involved is called the hypothalamic-pituitary-adrenal (HPA) axis. Under normal conditions, the hypothalamus signals the pituitary gland to release adrenocorticotropic hormone (ACTH), which in turn tells the adrenal glands—small organs located near the kidneys—to produce cortisol. In a healthy dog, rising cortisol levels feed back to the pituitary to slow ACTH release, keeping everything in balance. Cushing's disease disrupts this feedback loop. A tumor on the pituitary gland (the most common cause, accounting for roughly 80–85 percent of cases) continuously secretes ACTH regardless of cortisol levels, or a tumor on one of the adrenal glands directly overproduces cortisol. A third form, iatrogenic Cushing's, results from the long-term use of corticosteroid medications such as prednisone.

The result is a body perpetually flooded with cortisol, leading to muscle wasting, immune suppression, skin changes, organ stress, and a cascade of secondary health problems if left untreated.

Symptoms of Cushing's Disease (Hyperadrenocorticism) in Dogs

Cushing's disease is sometimes called "the great imitator" because its symptoms overlap with many other conditions and with normal aging. Recognizing the pattern of multiple concurrent symptoms is key.

Early Signs

These are typically the first changes owners notice, often developing over weeks to months:

• Increased thirst (polydipsia) — Drinking noticeably more water than usual; seeking out unusual water sources.
• Increased urination (polyuria) — More frequent urination, larger volumes, and possible house-soiling or nighttime accidents in previously house-trained dogs.
• Increased appetite (polyphagia) — Begging for food, scavenging, or acting ravenous even after meals.
• Panting — Excessive or inappropriate panting, even at rest or in cool environments.
• Mild lethargy — Reduced enthusiasm for walks or play, sleeping more.
• Gradual weight gain — Particularly around the abdomen.

Progressive Symptoms

As cortisol levels remain elevated over months, more visible and systemic signs develop:

• Pot-bellied appearance — A distended, pendulous abdomen caused by weakened abdominal muscles and fat redistribution; one of the hallmark signs.
• Hair loss (alopecia) — Bilateral, symmetrical hair loss on the trunk, flanks, and neck, typically sparing the head and legs. The coat may become dull and fail to regrow after clipping.
• Thin, fragile skin — The skin becomes noticeably thinner, bruises easily, and may develop dark pigmentation (hyperpigmentation) or comedones (blackheads).
• Recurrent skin and urinary infections — Cortisol suppresses the immune system, making bacterial skin infections (pyoderma) and urinary tract infections common and difficult to resolve.
• Muscle weakness and wasting — Dogs may struggle with stairs, have difficulty jumping, or show a stiff, slow gait.
• Calcinosis cutis — Hard, calcium deposits that form in the skin, appearing as raised, white or grayish plaques, most often on the back, groin, or neck.
• Delayed wound healing — Cuts, scratches, and surgical incisions heal slowly.
• Reproductive changes — Testicular atrophy in males; irregular or absent heat cycles in intact females.

Emergency Signs

Seek immediate veterinary care if you observe:

• Sudden blindness — Can result from hypertension-related retinal detachment.
• Blood clots (thromboembolism) — Signs include sudden collapse, difficulty breathing, or painful, cold limbs. Cushing's creates a hypercoagulable state.
• Signs of a macroadenoma (large pituitary tumor) — Neurological symptoms such as circling, head pressing, disorientation, seizures, or sudden behavior changes.
• Diabetic crisis — Cushing's disease is a significant risk factor for diabetes mellitus. Watch for vomiting, extreme lethargy, and sweet-smelling breath.
• Acute abdominal distress — Sudden severe pain, vomiting, or collapse, which could indicate adrenal tumor rupture or pancreatitis.

What Causes Cushing's Disease (Hyperadrenocorticism) in Dogs?

Pituitary-Dependent Hyperadrenocorticism (PDH)

Approximately 80–85% of naturally occurring Cushing's cases are caused by a benign tumor (adenoma) of the pituitary gland. This tumor secretes excessive ACTH, overstimulating both adrenal glands. Pituitary tumors are usually small (microadenomas), but in roughly 10–20% of PDH cases the tumor can grow large enough (macroadenoma) to compress surrounding brain tissue and cause neurological symptoms.

Adrenal-Dependent Hyperadrenocorticism (ADH)

In 15–20% of cases, a tumor develops directly on one of the adrenal glands. Approximately half of adrenal tumors are benign adenomas, while the other half are malignant carcinomas. Adrenal carcinomas can invade surrounding blood vessels and metastasize, making early detection important.

Iatrogenic Cushing's Syndrome

Long-term or high-dose administration of glucocorticoid medications (prednisone, prednisolone, dexamethasone) can produce the same clinical picture. This form resolves when the medication is gradually tapered under veterinary supervision—abrupt withdrawal is dangerous because the adrenal glands atrophy during steroid use and need time to resume normal cortisol production.

Risk Factors

• Age — Most dogs are diagnosed between 8 and 12 years old; it is uncommon in dogs under 6.
• Genetics — Certain breeds carry a higher predisposition (see below), suggesting a hereditary component.
• Obesity — While not a direct cause, obesity can complicate diagnosis and worsen outcomes.
• Chronic steroid use — Dogs on long-term corticosteroids for allergies, autoimmune diseases, or inflammatory conditions are at risk for the iatrogenic form.

Breeds Most at Risk

While any dog can develop Cushing's disease, certain breeds are diagnosed at disproportionately high rates, strongly suggesting a genetic predisposition:

• Poodles (Miniature and Toy) — Among the most frequently affected breeds.
• Dachshunds — Consistently overrepresented in studies.
• Beagles — Common in both clinical and research settings.
• Boston Terriers — Higher incidence noted in breed-specific studies.
• Boxers — Predisposed to both pituitary and adrenal forms.
• Yorkshire Terriers — Small breeds in general are more prone to PDH.
• Staffordshire Bull Terriers — Increasingly recognized as predisposed.
• Labrador Retrievers and German Shepherds — While large breeds are less commonly affected overall, these breeds appear in cases at notable rates, and large-breed dogs are more likely to have adrenal tumors specifically.
• Maltese and Bichon Frise — Small companion breeds with elevated risk.
• Dandie Dinmont Terriers — One of the highest per-capita breed incidences.

How Cushing's Disease (Hyperadrenocorticism) Is Diagnosed

Cushing's disease is one of the more challenging endocrine conditions to diagnose definitively. No single test is 100% accurate, so veterinarians rely on a combination of clinical signs, blood work, and specialized hormonal tests.

Step 1: Clinical Examination and History

The veterinarian will evaluate your dog's physical appearance (pot belly, skin changes, hair loss) and review history of increased drinking, urination, and appetite. A pattern of these signs together raises strong suspicion.

Step 2: Routine Blood Work and Urinalysis

• Complete blood count (CBC) — May show a "stress leukogram" (elevated neutrophils, low lymphocytes and eosinophils).
• Serum chemistry panel — Classic findings include elevated alkaline phosphatase (ALP), often dramatically so, elevated cholesterol and triglycerides, and mildly elevated blood glucose.
• Urinalysis — Dilute urine (low specific gravity) is a hallmark. Urine culture may reveal a silent urinary tract infection.
• Urine cortisol-to-creatinine ratio (UCCR) — A screening test performed on a morning urine sample collected at home. A normal result makes Cushing's unlikely; an elevated result warrants further testing but is not diagnostic on its own.

Step 3: Hormonal (Endocrine) Testing

• Low-dose dexamethasone suppression test (LDDS) — Considered the gold standard screening test. A small dose of dexamethasone is injected, and cortisol levels are measured at 4 and 8 hours. In a healthy dog, cortisol is suppressed; in a dog with Cushing's, cortisol remains elevated. This test can also sometimes help differentiate pituitary from adrenal causes. Sensitivity is approximately 85–95%.
• ACTH stimulation test — A synthetic ACTH injection is given and cortisol is measured before and 1 hour after. This test is particularly useful for diagnosing iatrogenic Cushing's and for monitoring treatment response. Sensitivity is lower (around 60–85%) but specificity is reasonable.
• High-dose dexamethasone suppression test (HDDS) — Used after a positive LDDS to help distinguish pituitary from adrenal tumors. Pituitary tumors often show suppression at higher doses; adrenal tumors do not.
• Endogenous ACTH level — Measuring the dog's baseline ACTH level can help differentiate: elevated or normal ACTH suggests pituitary origin; low or undetectable ACTH suggests an adrenal tumor functioning independently.

Step 4: Diagnostic Imaging

• Abdominal ultrasound — Essential for evaluating adrenal gland size and symmetry. Bilateral enlargement suggests pituitary-dependent disease; a unilateral mass with atrophy of the opposite gland suggests an adrenal tumor. Also assesses liver size (hepatomegaly is common) and can detect other complications.
• CT scan or MRI — Recommended when a pituitary macroadenoma is suspected or if surgery is being considered. MRI is the preferred modality for visualizing the pituitary gland.
• Thoracic radiographs (chest X-rays) — Performed if an adrenal carcinoma is suspected, to check for pulmonary metastasis.

Treatment Options for Cushing's Disease (Hyperadrenocorticism)

Treatment depends on the type of Cushing's disease, the dog's overall health, and whether complications are present. The goal is to reduce cortisol to a safe level and manage symptoms.

Medical Management

Medical therapy is the most common approach, particularly for pituitary-dependent Cushing's.

• Trilostane (Vetoryl) — The most widely used medication worldwide. Trilostane inhibits the enzyme 3-beta-hydroxysteroid dehydrogenase, blocking cortisol synthesis in the adrenal glands. It is given once or twice daily with food. Dogs require regular ACTH stimulation tests (typically at 2 weeks, 4 weeks, 12 weeks, and then every 3–6 months) to ensure the dose is correct and cortisol levels are adequately controlled without going dangerously low. Most dogs show improvement in drinking, urination, and energy within 2–4 weeks; skin and coat changes may take 3–6 months to resolve.
• Mitotane (Lysodren) — An older drug that selectively destroys the cortisol-producing layers of the adrenal cortex. Effective but carries a higher risk of side effects, including Addisonian crisis (dangerously low cortisol). It requires a carefully monitored induction phase followed by maintenance dosing. Used less frequently now but remains an option when trilostane is ineffective or unavailable.
• Selegiline (Anipryl) — Approved for the treatment of pituitary-dependent Cushing's, selegiline works by modulating dopamine in the brain. It is significantly less effective than trilostane or mitotane and is generally reserved for mild cases or when other medications are not tolerated.

Surgical Options

• Adrenalectomy — Surgical removal of a tumor-bearing adrenal gland is the treatment of choice for adrenal-dependent Cushing's when the tumor is operable. When performed by an experienced surgeon, outcomes can be excellent—potentially curative for benign adenomas. However, adrenal surgery is complex and carries significant risks, including hemorrhage and postoperative Addisonian crisis. Dogs typically require intensive postoperative monitoring and temporary cortisol supplementation.
• Transsphenoidal hypophysectomy — Surgical removal of the pituitary tumor. This procedure is technically demanding and only available at a few specialized veterinary centers worldwide. When successful, it can be curative for PDH, but it requires lifelong hormone supplementation.
• Radiation therapy — Used primarily for large pituitary macroadenomas causing neurological symptoms. Radiation can shrink the tumor and alleviate brain compression. It does not always normalize cortisol levels, so concurrent medical management is often needed.

Alternative and Supportive Therapies

• Melatonin and lignans — Some holistic veterinarians recommend flaxseed lignans and melatonin for dogs with mild or atypical Cushing's disease. These supplements may help modulate adrenal hormone production, but evidence is limited and they are not a substitute for standard treatment in moderate-to-severe cases.
• Nutritional support — A diet moderate in protein, low in fat, and rich in antioxidants may help support dogs with Cushing's. Omega-3 fatty acids can support skin and coat health. Consult your veterinarian before making dietary changes.
• Herbal and supplement therapies — Products containing phosphatidylserine, adaptogenic herbs, or adrenal-support blends are marketed for Cushing's, but clinical evidence supporting their efficacy is sparse. Always discuss supplements with your vet.

At-Home Care

• Ensure unlimited access to fresh water — Dogs with Cushing's cannot concentrate their urine and will drink excessively. Restricting water can lead to dangerous dehydration.
• Frequent bathroom breaks — Accommodate increased urination to prevent accidents and discomfort. Waterproof bedding or puppy pads can be helpful.
• Skin care — Bathe with gentle, medicated shampoos if your dog has skin infections. Keep skin folds clean and dry. Monitor for new lesions or calcinosis cutis.
• Gentle exercise — Maintain light, regular exercise to counteract muscle wasting, but avoid overexertion.
• Monitor and record symptoms — Track water intake, urination frequency, appetite, energy level, and body weight. Share these records with your veterinarian to guide dosage adjustments.
• Medication compliance — Give trilostane or other medications consistently with food at the same time each day. Never skip doses or adjust without veterinary guidance.

Prognosis and Life Expectancy

The prognosis for dogs with Cushing's disease depends on the underlying cause, the dog's age at diagnosis, the presence of complications, and how well the disease responds to treatment.

Untreated Cushing's disease is progressive and eventually life-threatening. Chronic cortisol excess leads to diabetes, uncontrollable infections, blood clots (pulmonary thromboembolism is a leading cause of death), hypertension, and organ failure. Treatment is strongly recommended for all symptomatic dogs.

Prevention

Cushing's disease is largely not preventable because the most common form is caused by spontaneous pituitary tumors. However, several strategies can help with early detection and risk reduction:

• Annual senior wellness exams — For dogs over 7 years old, yearly blood work including a chemistry panel and urinalysis can catch early indicators such as elevated ALP and dilute urine.
• Know your breed's risk — If you own a predisposed breed, discuss screening with your veterinarian, especially if you notice subtle changes in thirst, urination, or coat quality.
• Judicious use of corticosteroids — Work with your veterinarian to use the lowest effective dose of steroid medications for the shortest duration necessary. Discuss steroid-sparing alternatives for chronic conditions.
• Breeding considerations — Responsible breeders of predisposed breeds should be aware of the condition's hereditary tendencies and consider the health history of breeding lines.
• Maintain a healthy weight — While obesity does not cause Cushing's, keeping your dog at a healthy weight reduces metabolic stress and makes early symptoms easier to recognize.

Cost of Treatment

Cushing's disease is a lifelong condition (unless cured by surgery) and the costs are cumulative. Below are general ranges in the United States:

| Category | Estimated Cost Range | |---|---| | Initial diagnostic workup (blood work, urinalysis, hormonal tests) | $500–$1,500 | | Abdominal ultrasound | $300–$800 | | CT scan or MRI | $1,500–$3,000+ | | Trilostane (monthly medication) | $50–$200/month | | ACTH stimulation monitoring tests (every 3–6 months) | $150–$350 per test | | Adrenalectomy (surgery) | $3,000–$10,000+ | | Radiation therapy | $3,000–$7,000+ | | Annual ongoing management (medication + monitoring) | $1,000–$3,500 |

Costs vary significantly by geographic region, the complexity of the case, and whether specialist referral is needed. Pet insurance may cover a portion of diagnostics and treatment if the policy was purchased before symptoms appeared. Discuss payment options and treatment priorities with your veterinary team.

Frequently Asked Questions

Is Cushing's disease painful for dogs?

Cushing's disease itself is not typically painful in the way an injury is, but it causes considerable discomfort and reduced quality of life. Dogs may experience muscle weakness, chronic skin infections, constant thirst and hunger, and general malaise. Secondary complications like urinary infections or calcinosis cutis can be painful. Most owners report significant improvement in their dog's comfort and behavior once treatment is started.

Can Cushing's disease be cured?

It depends on the cause. Adrenal tumors (benign adenomas) can potentially be cured with surgery. Pituitary-dependent Cushing's is typically managed rather than cured, meaning lifelong medication is required to control cortisol levels. Iatrogenic Cushing's resolves when corticosteroid medications are appropriately tapered. Regardless of the form, effective management allows most dogs to live comfortably.

How quickly does treatment work?

Most owners notice a reduction in excessive thirst, urination, and appetite within 2–4 weeks of starting trilostane. Panting often improves within a similar timeframe. Skin and coat changes are slower to resolve, typically taking 3–6 months. A pot-bellied appearance gradually improves over several months as abdominal muscles regain strength.

What happens if Cushing's disease is left untreated?

Without treatment, Cushing's disease is progressive and ultimately life-threatening. Chronic cortisol excess weakens the immune system, making dogs vulnerable to serious infections. It also creates a hypercoagulable state that increases the risk of potentially fatal blood clots. Diabetes mellitus, pancreatitis, hypertension, and kidney disease can all develop as secondary complications. Quality of life deteriorates steadily.

Can a dog with Cushing's disease still live a good life?

Yes. With proper diagnosis and treatment, many dogs with Cushing's disease enjoy a good to excellent quality of life for years. The key is consistent medication, regular veterinary monitoring, and attentive at-home care. Most owners report that their dogs seem noticeably happier and more energetic once cortisol levels are controlled.

Are there side effects of trilostane?

Trilostane is generally well-tolerated, but side effects can occur. Mild side effects include decreased appetite, lethargy, and mild gastrointestinal upset, particularly when starting the medication or adjusting doses. The most serious risk is adrenal necrosis or an Addisonian crisis (dangerously low cortisol), which can present as vomiting, diarrhea, weakness, collapse, or refusal to eat. If you observe any of these signs, stop the medication and contact your veterinarian immediately. Regular monitoring tests help minimize this risk.

How is Cushing's disease different from Addison's disease?

They are opposite conditions. Cushing's disease involves too much cortisol; Addison's disease (hypoadrenocorticism) involves too little. Interestingly, treatment for Cushing's can occasionally cause Addison's if cortisol is suppressed too aggressively. Both conditions are manageable with appropriate medical care, and your veterinarian will monitor your dog carefully to maintain the proper hormonal balance.

Should I get my older dog tested for Cushing's?

If your senior dog is drinking and urinating more than usual, has a pot-bellied appearance, is losing hair symmetrically, or has recurrent infections, screening for Cushing's disease is worthwhile. These signs can also be caused by other conditions (diabetes, kidney disease, thyroid disorders), so testing helps your veterinarian reach the correct diagnosis. Routine senior wellness blood work can sometimes reveal early indicators even before obvious symptoms appear.