Here is the simplest way to explain Cushing’s disease in dogs.
The pituitary gland (at the base of the brain) produces a hormone called ACTH
ACTH stimulates the adrenal gland (on top of kidneys) to produce glucocorticoid hormones/corticosteroids (Cortisol)
Something goes wrong in the pituitary or adrenal glands
Too much cortisol is produced by the adrenals
Cushing’s disease develops
Who gets it and when
Dogs usually get Cushing’s when they’re around six, but it can really happen at any age. I have read reports that say it doesn’t discriminate based on sex or breed, and others that say breeds like Staffies, Beagles, Dachshunds, Yorkies, Poodles and Boxers are more prone, and females slightly more than males.
It sounds more like an opinion based on some vets’ experiences, than fact based on research. Even if it is fact, it certainly does not guarantee your dog will, or will not get Cushing’s if they do, or don’t, fall into any of the above categories, so I wouldn’t worry too much about this.
What role does cortisol play
- Helps your dog cope with physical and emotional stress
- Suppresses inflammation
- Helps with wound healing
- Supports muscle and ligament health
- Controls weight
- Necessary for proper brain function
- Maintains bone health
- Fights infection
- Maintains normal blood sugar (glucose) levels
Signs and Symptoms
Cushing’s comes on very slowly, and the first signs you tend to see are your dog having to drink and pee more frequently.
Other symptoms include:
- Increased hunger
- Weight gain
- Hair loss
- Pot belly
- Thinning skin
- Tired and inactive
- Skin infections
- Muscle loss
- Fat accumulation on the neck and shoulders
- Housebroken dogs may start to have accidents
- May bruise easily
- Bladder or kidney infections
- Susceptible to blood clots
There are two types of Cushing’s
This means the pituitary gland (pea sized gland at the base of the brain) is overproducing cortisol, due to a tumour or enlargement of the gland. It is the most common form, affecting around 80%-85% of dogs.
A tumour in one or both of the adrenal glands (that sit on top of the kidneys) is responsible for about 15%-20% of cases. About half of these will metastasize (spread).
A third type…
I did say there were two types, but “iatrogenic” Cushing’s disease occurs as a result of high doses of steroids, over a long period of time. Once the steroids are discontinued, symptoms should go away.
A dog must be gradually weaned off steroids over the course of several weeks. It is too dangerous to stop them abruptly.
How is Cushing’s diagnosed?
There is no single test, and because it has the same symptoms as other conditions, it can be difficult to diagnose.
Your vet will want to hear your concerns, and what new behaviours you’ve noticed. If you’re going to a new vet, he’ll also want a detailed history. Once that’s done he will exam your dog, and take blood and urine. The office may have even suggested you bring a urine sample with you.
These tests can detect the following which are common in dogs with Cushing’s:
- Elevated white blood cell count
- Increase in the liver enzyme ALP (alkaline phosphatase)
- Elevated blood sugar (but not as high as you would find in diabetes)
- Increased cholesterol
- Diluted urine
- Urinary tract infections
If the results are pointing in the direction of Cushing’s, then more tests will likely be done. Here are some of the options:
ACTH stimulation test
Blood is taken before and after a shot of ACTH, to see how the hormone affects your dog.
Low dose Dexamethasone suppression (LDDS) test
Blood is taken before and after a shot of a man made version of cortisol, called Dexamethasone.
When the shot is given, the pituitary gland should mistake it for cortisol and let the adrenal gland know to stop producing cortisol.
“Healthy” dogs show a significant decrease in blood cortisol levels when tested.
If the level remains high, your dog either has a pituitary tumour that continues to produce ACTH, or an adrenal tumour that continues to produce cortisol.
High Dose Dexamethasone Suppression Test
It is similar to the LDDS test, but a higher dose of Dexamethasone is given.
An ultrasound might detect an adrenal tumour, but they can be quite small and hard to see.
They can show 50% percent of adrenal tumours, and can be quite helpful in differentiating pituitary from adrenal.
Many vets choose not to begin treatment in very mild cases, because of their concern over the toxicity and side effects of the medications.
Most vets treat both adrenal- and pituitary-dependent Cushing’s disease with medication.
Treatment of Pituitary Dependent Cushing’s
Drugs are best for dogs with Cushing’s caused by the pituitary gland, or for those with a tumour on their adrenal gland that can’t be removed with surgery.
Surgery isn’t typically done, since the pituitary gland is in a very hard to reach spot. It would, however, be done in cases of very large tumours that are causing serious issues like seizures, blindness, personality changes…
Radiation therapy may be an option for some dogs. It will destroy the pituitary tumour, but do a host of other damage at the same time.
Treatment of Adrenal Dependent Cushing’s
Removal of the cancerous adrenal gland, however, it is tricky surgery with post-op complications, and not commonly done. The tumours are often impossible to see, and are sometimes malignant so have already spread.
Treatment of iatrogenic Cushing’s syndrome
Your vet will advise you on how to gradually stop giving your dog steroids, but the original condition they were treating will probably come back
Once the condition is managed, dogs with Cushing’s can live good quality lives. Obviously only your vet can give you a better idea based on his findings.
Life with Cushing’s
- Follow your dog’s treatment plan to the letter
- Regular vet checks and testing
- Keep a close watch on behaviour and symptoms
- Good nutrition
- Low stress, quiet life
- Watch for any reactions to medications like lethargy, loss of appetite, vomiting, diarrhea… and call your vet immediately.
Cushing’s Disease in Older Dogs – conclusion
I hope you found this post about Cushing’s disease in older dogs helpful.
Does your dog have Cushing’s? How quickly was it diagnosed? How, if at all, has life changed for your dog and for you?