Cushing’s disease (also known as hypercortisolism or hyperadrenocorticism) is a hormone disorder. The latest data shows that it affects between 0.20-0.28 percent of dogs.
This condition occurs when the body produces the hormone cortisol (a steroid hormone) in excess.
Cortisol is best known as a stress hormone, but it also has several other responsibilities. It manages how the body processes carbohydrates, proteins, and fats, regulates blood pressure, and influences the sleep-wakefulness cycle.
Cushing’s disease can contribute to many serious health issues without proper treatment, so it’s important to catch and address it as soon as possible.
If you’ve never heard of Cushing’s disease or aren’t sure if it’s the source of your dog’s symptoms, this guide can help. It breaks down everything you need to know about Cushing’s disease in dogs, from the condition’s symptoms to its prognosis.
What Are the Symptoms of Cushing’s Disease?
Cushing’s disease can occur at any age but generally affects middle-aged and senior dogs. The following are some of the most well-known symptoms associated with this condition:
- Increased thirst and hunger
- Increased urination and indoor accidents, even among housebroken dogs
- Hair loss or slowed hair growth
- Developing a pot belly
- Thinning skin
- Increased fatigue and decreased activity
- Increased panting
- More frequent skin infections
Often, increased thirst and urination are the first signs that something is wrong.
Cushing’s disease triggers excessive thirst, which causes dogs to drink more and then urinate more often. They might even start waking you up in the middle of the night to go out, despite typically being able to make it through the night without a bathroom break.
It’s also worth noting that it often takes at least a year for Cushing’s disease symptoms to show up. The warning signs come on gradually and may be mistaken for regular signs of aging, escalating the condition before it’s diagnosed.
What Are the Different Types of Cushing’s Disease?
Cushing’s disease comes in three forms — pituitary-dependent, adrenal-dependent, and iatrogenic:
Pituitary-Dependent Cushing’s Disease
Pituitary-dependent Cushing’s disease is the most common type. It is caused by a tumor on a pea-sized pituitary gland located at the base of the brain.
The pituitary gland might be tiny, but it is still a critical endocrine gland that regulates hormone production.
Adrenal-Dependent Cushing’s Disease
Adrenal-dependent Cushing’s disease results from a tumor in one of the adrenal glands. These small glands sit above the kidneys and produce various hormones, including cortisol.
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Iatrogenic Cushing’s Disease
Iatrogenic Cushing’s disease is the least common type. It is caused by prolonged steroid medication consumption.
Veterinarians might prescribe ongoing steroid medications to manage autoimmune conditions like Addison’s disease or lupus.
What Are the Causes of Cushing’s Disease?
The cause of iatrogenic Cushing’s disease is the clearest. This condition results from long-term use of steroid medications.
However, veterinarians and researchers aren’t entirely sure what causes the tumors that lead to pituitary-dependent and adrenal-dependent Cushing’s disease. What they do know, though, is what happens to a dog’s body once these tumors occur.
When a tumor forms on the pituitary gland, the gland overproduces the hormone ACTH (short for adrenocorticotropic hormone). ACTH stimulates the adrenal glands and causes them to produce more cortisol.
When a tumor forms on one of the adrenal glands, it can also trigger them to produce large amounts of cortisol.
Which Breeds Are More Susceptible to Cushing’s Disease?
Dogs of all breeds can develop Cushing’s disease. However, researchers have found that some breeds are more susceptible than others, including the following:
- Poodles (especially miniature poodles)
- Dachshunds
- Boston terriers
- Boxers
- Beagles
- Cocker spaniels
With all these breeds, female dogs are more prone to Cushing’s disease than males. Senior dogs (those eight years and older) of both genders also face an increased risk.
Even if your dog isn’t an at-risk breed, you should still look for signs of Cushing’s disease, especially as they age.
How Is the Disease Diagnosed?
You should reach out to a veterinarian as soon as possible after noticing potential indicators of Cushing’s disease.
During your dog’s appointment, a veterinarian will use a few different techniques for diagnosing Cushing’s disease. These are the most common approaches:
Blood and Urine Tests
Often, when you present a dog with symptoms like increased hunger, thirst, urination, and fatigue, the veterinarian starts with blood work and urine tests.
These tests help veterinarians identify elevated enzyme levels (particularly the enzyme group known as alkaline phosphatase).
If enzyme levels are above the normal range, Cushing’s disease might be the culprit.
ACTH Stimulation Test
An ACTH stimulation test measures adrenal gland function.
This test involves administering a shot of ACTH to see what the adrenal glands do when ACTH levels increase. The vet will also take blood samples before and after the injection to see how the hormone influenced their cortisol levels.
Ideally, the dog’s cortisol would rise slightly in response to the ACTH. If it increases significantly and continues to climb, that’s a sign of Cushing’s disease.
Low-Dose Dexamethasone Suppression Test (LDDST)
A Low-Dose Dexamethasone Suppression Test (LDDST) assesses the dog’s response to dexamethasone, a manufactured version of cortisol.
Similar to the ACTH stimulation test, the vet will take blood samples before and after administering a shot of dexamethasone to see how the body handles it.
The cortisol levels should rise slightly and then decrease. If they stay elevated, Cushing’s disease is likely.
Abdominal Ultrasound
Some veterinarians also perform an ultrasound scan on the dog’s abdomen. This scan lets them know if a tumor is present on the adrenal glands and helps them determine how they should proceed.
Treatment Options for Cushing’s Disease
Cushing’s disease cannot be cured. The good news, though, is that it’s treatable, especially when you catch it early.
Depending on the cause of your dog’s condition, veterinarians might use the following techniques to manage their symptoms and improve their quality of life:
Surgery
If a veterinarian diagnoses your dog with adrenal-dependent Cushing’s disease, surgery might be an option. The surgery is complex and expensive, but it can also reduce symptoms and improve your dog’s quality of life.
Surgery is especially crucial for dogs with malignant adrenal tumors. These tumors grow aggressively and metastasize quickly.
Medication
Medication for dogs with pituitary tumors tends to be more effective (and less risky) than surgery.
Oral medications like Mitotane (brand name Lysodren) and trilostane (brand name Vetoryl) work by destroying a portion of the adrenal cortex.
The idea of destroying a part of the adrenal cortex might sound scary at first. However, it has positive effects.
Even though the pituitary gland is still releasing ACTH, cortisol levels will remain within a normal range, lessening your dog’s symptoms.
After they start medication, veterinarians must carefully monitor the dog to ensure all of the adrenal cortex isn’t destroyed and that their cortisol levels stay within a healthy range.
Medication Reduction
If a dog’s Cushing’s disease results from excessive steroid consumption, veterinarians might respond by slowly tapering them off the steroid medication. However, they will also have to weigh the benefits of this approach against the risk of the symptoms the steroids are treating coming back.
You and your vet will have to work together to decide which option (continuing with the steroids or weaning off them) is better for your dog’s overall health and quality of life.
What to Expect from Cushing’s Disease Treatment
Once your dog has received a Cushing’s disease diagnosis, they’ll require intensive treatment to get their symptoms under control. The treatment is particularly rigorous in the initial months following the diagnosis.
For those treating their dog’s condition with medication, the vet will likely require regular ACTH stimulation tests (every few weeks) to ensure it’s appropriately dosed and working correctly. They might also recommend ongoing blood and urine tests to monitor the dog’s kidney and liver function.
Once the dog seems to be responding to medication, the veterinarian will recommend reducing test frequency to every 6-12 months.
If your dog undergoes surgery to remove the tumor, they will need increased support while they recover. They’ll also need medication and ongoing monitoring to ensure they respond well to the procedure.
Cushing’s Disease Prognosis
Cushing’s disease progresses slower than some other conditions. If it’s promptly diagnosed and adequately treated, dogs live for about two years on average. Some survive up to four years and beyond.
Without treatment, dogs with Cushing’s disease are more likely to develop other severe conditions, including the following:
- Elevated blood pressure
- Pulmonary thromboembolism
- Congestive heart failure
- Neurological symptoms (such as seizures)
- Blindness
- Myopathy
- Diabetes
It’s also worth noting that Cushing’s disease is not always the direct cause of death. Because this condition affects senior dogs, they’re more likely to pass away from other issues associated with aging.
Do You Suspect Your Dog Has Cushing’s Disease?
Now that you know more about Cushing’s disease in dogs, do you think it could be behind your dog’s symptoms? If so, reach out to a licensed veterinarian to get their insight.
A video consultation with one of Cooper Pet Care’s qualified veterinarians is only a few clicks away. Fast, simple, and secure – get the answers you need.