Adrenal Gland Problems in Dogs: Cushing's, Addison's and Adrenal Tumors

What Do a Dog's Adrenal Glands Do?

A dog has two adrenal glands, one just in front of each kidney. Each has two parts:¹

• The cortex (outer layer) makes cortisol, which helps the body handle stress and regulates blood sugar, metabolism and inflammation; aldosterone, which keeps sodium and potassium in balance and maintains blood pressure; and small amounts of sex hormones.
• The medulla (center) makes epinephrine (adrenaline) and norepinephrine, the "fight or flight" hormones that raise heart rate and blood pressure.

The pituitary gland at the base of the brain controls cortisol production by releasing a hormone called ACTH. That is why a pituitary problem can cause adrenal disease.

Cushing's vs. Addison's Disease at a Glance

Sources: Merck Veterinary Manual, Cornell, Today's Veterinary Practice.^2,3,4,5

Cushing's Syndrome (Hyperadrenocorticism)

Cushing's is one of the most common hormonal diseases in middle-aged and older dogs. It develops when the body is exposed to too much cortisol for a long time.¹

Causes

• Pituitary-dependent Cushing's (about 80–85% of cases): a small, usually benign tumor in the pituitary gland releases too much ACTH, which drives both adrenal glands to overproduce cortisol.^6,7
• Adrenal-dependent Cushing's (about 15–20%): a tumor in one adrenal gland makes cortisol on its own.^6,7
• Iatrogenic Cushing's: caused by long-term steroid medications such as prednisone. It usually improves when the steroid is slowly tapered under your vet's direction; never stop a steroid suddenly.^1,4

Which dogs get Cushing's?

Most dogs are 7–12 years old. Pituitary Cushing's is most common in smaller breeds such as Miniature Poodles, Dachshunds, Yorkshire Terriers, Bichon Frises, Miniature Schnauzers, Jack Russell and Boston Terriers, and also Boxers. Adrenal tumors are relatively more common in larger dogs such as German Shepherds and Staffordshire Terriers.^3,4

Signs of Cushing's

• Drinking and urinating much more than usual (in 80–90% of dogs), sometimes with accidents in the house
• A big appetite and begging or scavenging for food
• A pot-bellied appearance from an enlarged liver and weak abdominal muscles
• Panting, even at rest
• Thinning hair or hair loss on both sides of the body that doesn't grow back after clipping
• Thin skin, blackheads, bruising, and hard white or gritty skin plaques (calcinosis cutis)
• Muscle weakness and tiring easily

Signs develop slowly and are often mistaken for normal aging.^4,8

Complications

Untreated Cushing's raises the risk of urinary tract and skin infections, diabetes (about 10% of dogs with Cushing's also have diabetes), high blood pressure, blood clots in the lungs, torn knee ligaments and gallbladder mucoceles. One study found dogs with Cushing's were 29 times more likely to have a gallbladder mucocele.^3,9

How vets diagnose Cushing's

No single test is perfect, so vets combine the history, exam, routine blood and urine tests, and specific hormone tests. Testing is recommended only for dogs with typical signs.⁸

• Routine blood work and urinalysis: a high liver enzyme called alkaline phosphatase (ALP), high cholesterol, and dilute urine are common clues.
• Urine cortisol:creatinine ratio: a home-collected urine sample. A normal result makes Cushing's unlikely, but a high result is not specific.
• Low-dose dexamethasone suppression test (LDDST): the preferred screening test, detecting 85–100% of cases.
• ACTH stimulation test: less sensitive, especially for adrenal tumors, but the test of choice for steroid-induced Cushing's and for monitoring treatment.
• Abdominal ultrasound and endogenous ACTH: help tell pituitary from adrenal Cushing's, which matters because adrenal tumors may be treated with surgery.

Treatment

• Trilostane (Vetoryl): the only FDA-approved drug for both pituitary and adrenal Cushing's. It is given with food once or twice daily, starting at a low dose. Your vet will recheck a blood test (an ACTH stimulation test or a pre-pill cortisol) about 10–14 days after starting and after any dose change, then every few months. Stop the drug and call your vet if your dog has poor appetite, vomiting, diarrhea, weakness or lethargy, which can signal cortisol has dropped too low.^3,7,10
• Mitotane (Lysodren): an older human drug that destroys part of the adrenal cortex. It is still used in some cases but has largely been replaced by trilostane.⁷
• Adrenalectomy: surgical removal of the affected gland is the treatment of choice for an adrenal tumor and can cure it.^1,4
• Pituitary surgery or radiation: available at a few specialty centers. Pituitary surgery leads to remission in about 80% of dogs; radiation is used mainly for large pituitary tumors causing neurologic signs.³

With treatment, thirst, urination and appetite usually improve within weeks, while the coat and skin can take several months. Dogs with pituitary Cushing's on medication live a median of about 2–2.5 years after diagnosis, and many die of unrelated diseases of old age. In one study, untreated dogs lived a median of 506 days, and treated dogs significantly longer.^3,4,11 For more detail, see our pages on Cushing's disease in dogs and does my dog have Cushing's?

Addison's Disease (Hypoadrenocorticism)

Addison's disease is the opposite of Cushing's: the adrenal glands don't make enough cortisol and, in most dogs, not enough aldosterone. It is usually caused by the immune system destroying the adrenal cortex. Without aldosterone, sodium falls and potassium rises, which can dangerously slow the heart.^1,2

Which dogs get Addison's?

Addison's mostly affects young to middle-aged dogs (median age about 4 years), and 60–70% are female. Breeds at higher risk include Standard Poodles, Portuguese Water Dogs, Nova Scotia Duck Tolling Retrievers, Bearded Collies, Great Danes and West Highland White Terriers.^2,5

Signs of Addison's

Vets call Addison's "the great pretender" because its signs are vague and come and go, often flaring with stress such as boarding or travel:^2,12

• Poor appetite, weight loss, vomiting and diarrhea
• Lethargy, weakness or shaking
• Increased thirst and urination
• Signs that seem to improve with fluids or steroids, then return

It is often mistaken at first for gastrointestinal or kidney disease.

Addisonian crisis

Many dogs are first diagnosed during a crisis: sudden collapse, shock, a slow heart rate (sometimes 50 beats per minute or lower) from high potassium, low blood sugar and severe vomiting or diarrhea. Emergency treatment with IV fluids, an injectable steroid and treatment of the high potassium usually brings rapid improvement.^1,2

Diagnosis

Blood tests often show low sodium and high potassium (a sodium:potassium ratio below 27 is suggestive). A resting cortisol level above 2 µg/dL effectively rules Addison's out; the ACTH stimulation test confirms it when cortisol stays very low (2 µg/dL or less) after stimulation.^2,5

"Atypical" Addison's disease

Some dogs are short of cortisol but still have normal sodium and potassium. This is now called eunatremic, eukalemic hypoadrenocorticism (EEH), and accounts for roughly 20% of cases in recent studies. These dogs mainly have gastrointestinal signs and can be harder to diagnose. Many go on to lose aldosterone too, sometimes within weeks or months, so electrolytes need regular rechecks.^5,13

Treatment

• DOCP injections (Percorten-V or Zycortal): replace aldosterone. Given about every 3–4 weeks, at the clinic or by owners at home.^14,15
• Prednisone or prednisolone: a small daily dose to replace cortisol, increased during stressful events such as surgery, boarding or illness. Dogs with atypical Addison's may need only this.^5,14
• Fludrocortisone (Florinef): a daily pill that replaces aldosterone; about half of dogs on it also need prednisone.⁵

Treatment is lifelong: the adrenal glands do not recover. With consistent treatment and monitoring, the outlook is excellent and most dogs live a normal lifespan.^1,12 See our page on canine Addison's disease.

Adrenal Gland Tumors in Dogs

In a large 2023 study of surgically removed adrenal tumors, 43% were adrenocortical carcinomas (cancer), 37% were adenomas (benign) and 18% were pheochromocytomas.¹⁶

• Cortisol-secreting tumors cause adrenal-dependent Cushing's (see above).
• Pheochromocytomas arise in the medulla and release bursts of adrenaline-like hormones. Signs come and go: panting, restlessness, a racing heart, weakness, collapse, and high blood pressure that can damage the eyes and kidneys. They often invade nearby blood vessels and spread in at least a quarter of cases.¹⁷
• Other tumors secrete aldosterone or sex hormones, or produce no hormones at all.

Incidental adrenal masses

Adrenal lumps are found by chance in about 4% of dogs having an abdominal ultrasound and about 9% on CT. Most small masses (under 2 cm) are benign; about 30% of larger ones are malignant. Vets typically recommend removing masses over 2 cm, growing masses or those producing hormones, and rechecking smaller ones with repeat imaging.¹⁸

Surgery and outlook

Adrenalectomy is the main treatment. Outcomes have improved considerably: in recent studies, about 95% of dogs having planned surgery for non-invasive tumors survived to go home, and disease-specific survival was about 89% at 2 years. Risk is much higher when the tumor has invaded the vena cava or when surgery is done as an emergency.^16,19,20 For pheochromocytoma, giving a blood-pressure medication (phenoxybenzamine) for 1–2 weeks before surgery improved survival to discharge from 85% to 98%, and dogs having surgery lived a median of 927 days compared with 247 days on medication alone.^17,21

Natural Remedies and "Adrenal Support" Supplements

Homeopathic and herbal "adrenal support" products, such as Cushex, have no published clinical evidence that they treat Cushing's or Addison's in dogs, and they are not FDA-approved.²² "Adrenal fatigue" is not a recognized diagnosis in veterinary medicine. Melatonin and flaxseed lignans are sometimes suggested for "atypical Cushing's" and hair loss, but evidence is limited to preliminary laboratory research.²³ Never use a supplement in place of diagnosis and treatment: untreated Addison's can be fatal, and untreated Cushing's leads to serious complications.

Frequently Asked Questions

What are the symptoms of adrenal gland problems in dogs?

Overactive adrenals (Cushing's) cause increased thirst, urination and appetite, a pot belly, panting and thinning hair. Underactive adrenals (Addison's) cause vomiting, diarrhea, poor appetite, weight loss and weakness that comes and goes, and can lead to sudden collapse. Adrenal tumors can cause either pattern, or episodes of panting, restlessness and a racing heart (pheochromocytoma).

How do vets check a dog's adrenal glands?

With routine blood and urine tests, hormone tests (the low-dose dexamethasone suppression test for Cushing's and the ACTH stimulation test for Addison's), and imaging, usually an abdominal ultrasound, to measure the glands and look for tumors.

What does it mean if my dog has enlarged adrenal glands?

Both glands enlarged usually points to pituitary-dependent Cushing's or long-term stress or illness. One enlarged gland, especially with a shrunken gland on the other side, suggests an adrenal tumor. Your vet will interpret the ultrasound together with hormone tests.

What is the life expectancy of a dog with Cushing's disease?

Dogs with pituitary Cushing's on treatment live a median of about 2–2.5 years after diagnosis, and many die of unrelated conditions since most are already older. Dogs whose adrenal tumor is successfully removed can be cured.

Is it worth treating a dog with Cushing's disease?

Usually, yes, if signs affect your dog's quality of life. Treatment reduces thirst, accidents, hunger and panting and lowers the risk of complications such as infections, diabetes and blood clots. Dogs with only mild signs may be monitored and treated if signs progress.

Are dogs in pain with Cushing's disease?

Cushing's itself is not usually painful, but it can make dogs uncomfortable through muscle weakness, panting, skin and urinary infections and, less often, torn ligaments or blood clots. Tell your vet about any limping, difficulty breathing or sudden changes.

What are the warning signs of an Addisonian crisis?

Sudden weakness or collapse, shaking, repeated vomiting or diarrhea (sometimes bloody), a slow heart rate, pale gums and cold legs. This is an emergency; go to the nearest vet immediately.

What can Addison's disease be mistaken for?

Gastrointestinal disease, kidney disease and pancreatitis are the most common look-alikes, because the signs are vague and come and go. A simple resting cortisol blood test can rule Addison's in or out.

Can a dog's adrenal glands heal themselves?

Usually not. Addison's disease requires lifelong hormone replacement. Steroid-induced Cushing's improves once the steroid is gradually withdrawn, and a dog whose adrenal tumor is removed can be cured, but pituitary Cushing's needs ongoing treatment.

Which dog breeds get adrenal problems?

Cushing's is common in Poodles, Dachshunds, Boxers, Boston Terriers, Yorkshire Terriers and other small terriers. Addison's is more common in Standard Poodles, Portuguese Water Dogs, Nova Scotia Duck Tolling Retrievers, Bearded Collies, Great Danes and West Highland White Terriers. Any breed or mixed breed can be affected.

Brochures

How to locate canine adrenal glands (PDF, source: UC Davis)
Cushing's disease in dogs (PDF, source: UC Davis)