Understanding Cushing’s Disease in Dogs
Cushing’s disease, also known as hyperadrenocorticism, is a complex endocrine disorder that affects many middle-aged and older dogs. It occurs when the body produces too much of the hormone cortisol. While cortisol is essential for normal bodily functions—helping manage stress, metabolism, and immune responses—its chronic overproduction can wreak havoc on a dog’s health.
What Causes Cushing’s Disease?
There are three main types of Cushing’s disease in dogs:
- Pituitary-dependent Cushing’s: This is by far the most common form (about 80–90% of cases). It results from a benign (or sometimes malignant) tumor in the pituitary gland at the base of the brain. The tumor triggers excessive release of adrenocorticotropic hormone (ACTH), which signals the adrenal glands to pump out more cortisol than needed.
- Adrenal-dependent Cushing’s: Making up about 10–20% of cases, this type stems from a tumor—either benign or malignant—on one or both adrenal glands. The tumor itself causes these glands to secrete excess cortisol.
- Iatrogenic (medication-induced) Cushing’s: This form isn’t caused by tumors but by long-term or high-dose use of corticosteroid medications prescribed for other conditions. These drugs mimic cortisol and can lead to similar symptoms if used excessively.
Main Symptoms to Watch For
Cushing’s disease develops gradually, so its signs can be mistaken for normal aging. However, there are several hallmark symptoms you might notice:
- Increased appetite and food seeking
- Excessive thirst and more frequent urination
- Hair loss or thinning coat (especially on the sides and tail)
- Thin, easily bruised skin
- A pot-bellied or bloated-looking abdomen
- Muscle weakness and overall lethargy
- Increased panting—even at rest
- Frequent skin or urinary tract infections
- Dark patches on the skin and slow-healing wounds
- Weight gain or trouble losing weight despite diet changes
The severity and combination of symptoms vary from dog to dog. Some may only show mild changes; others develop multiple issues that impact their quality of life.
How Is Cushing’s Disease Diagnosed?
The symptoms above aren’t unique to Cushing’s disease—they overlap with many other illnesses. That’s why your veterinarian will use a combination of history, physical exam findings, and specific laboratory tests to confirm the diagnosis. Common diagnostic steps include:
- Bloodwork and urine tests: These look for elevated liver enzymes, high cholesterol, dilute urine, protein in urine, or signs of infection/stress.
- ACTH stimulation test: Measures how well the adrenal glands respond after being stimulated with synthetic ACTH.
- Low-dose dexamethasone suppression test (LDDS): Assesses whether cortisol levels drop appropriately after giving dexamethasone.
- High-dose dexamethasone suppression test: Sometimes used to help distinguish between pituitary- and adrenal-dependent forms.
- Abdominal ultrasound or advanced imaging (CT/MRI): Helps locate tumors on either the pituitary or adrenal glands.
No single test gives all the answers; often several are needed to confirm Cushing’s disease and determine its cause.
Treatment Options for Dogs with Cushing’s Disease
Treatment depends on which type your dog has:
- Pituitary-dependent cases: Most are managed with daily medication for life. The most common drug is trilostane (Vetoryl), which blocks excess cortisol production. Mitotane (Lysodren) may also be used but works by destroying part of the adrenal cortex.
- Adrenal-dependent cases: If caused by an adrenal tumor that hasn’t spread elsewhere, surgery to remove the affected gland can be curative—but it carries risks and requires specialized care.
- Iatrogenic cases: Gradual withdrawal from corticosteroid medications under veterinary supervision is key; however, this may cause recurrence of whatever condition required steroids initially.
- Radiation therapy: Sometimes considered for large pituitary tumors causing neurological symptoms.
Lifelong Management & Monitoring
Cushing’s disease typically isn’t curable unless a non-malignant adrenal tumor is completely removed. Most dogs require ongoing medication and regular checkups for optimal management. Here’s what ongoing care usually involves:
- Lifelong medication: Dose adjustments may be needed based on periodic ACTH stimulation tests and bloodwork results.
- Regular veterinary visits: Early in treatment these are frequent; once stable they’re spaced every three to six months.
- Dose monitoring: Too much medication can cause Addison’s disease (too little cortisol); too little won’t control symptoms effectively.
- Your role as an owner: Watch for changes in drinking habits, urination frequency, appetite, energy level, skin/coat quality—and report anything unusual promptly to your vet.
If Left Untreated...
Cushing’s disease leads to poor quality of life: immune suppression leaves dogs prone to infections; muscle wasting progresses; complications such as diabetes or blood clots may develop; organ failure becomes likely over time. Without intervention, most affected dogs eventually succumb to these complications.
Lifespan & Prognosis After Diagnosis
The outlook varies depending on underlying cause and response to treatment. Many dogs live several happy years with proper management—especially if their case is caught early and monitored closely. Prognosis worsens if large/malignant tumors are present or other serious illnesses coexist.
Affected Breeds & Prevention Tips
Poodles, Dachshunds, Yorkshire Terriers—and some other small breeds—seem particularly susceptible. However, any dog can develop Cushing’s disease as they age. There isn’t any way to prevent pituitary- or adrenal-based forms; iatrogenic cases can be avoided by using steroid medications only when truly necessary—and always at the lowest effective dose for the shortest possible period.
