What is Cushing’s Disease?
Cushing’s disease in dogs happens when their body produces high cortisol levels in the blood. Cortisol is a hormone that helps dog body to respond to stress, fight infections and control blood sugar levels in the body.*
Cushing’s disease is also called hypercortisolism and hyperadrenocorticism. This disease can happen to both humans and animals.†
What Are The Types of Cushing’s Disease/Syndrome:
There are three types of Cushing’s disease that affect dogs:
- Pituitary Gland Related: This type of Cushing’s disease is the most common and affects 80% to 90% of the animals. This happens when there is a tumour (malignant or benign) over pituitary gland which is placed at the base of the brain.‡
2. Adrenal Gland Related: This type affects 10% to 15% of the animals. This happens when there is a tumour (malignant or benign) on top of adrenal glands which sits just above kidneys. §
3. Iatrogenic Type: This happens only in dog’s who have been given steroids due to some medical condition and over a period of time Cushing’s disease has happened.¶
Why does Cushing’s Disease in dogs happen?
In a healthy dog, ACTH hormone is secreted by the pituitary gland that stimulates the adrenal glands to produce cortisol. As the blood cortisol level increases, brain asks the pituitary gland to lower the production of ACTH, which in turn orders adrenal glands to produce less cortisol and hence reduce cortisol level in body – a controlling mechanism called a negative feedback loop#. In a dog with Cushing’s syndrome, this negative feedback loop don’t perform properly and hence there is excess of cortisol level in blood.
What Are The Symptoms Of Cushing’s Disease?
Following are the symptoms of Cushing’s disease however these symptoms can show up for different diseases too.** These symptoms will generally show up in middle-aged to old dogs.
- Extreme Thirst††
- Extra Hungry than usual‡‡
- Excess Urination§§
- Loses hair or it seems slow to grow¶¶
- Gets a pot belly due to fat buildup on organs
- Skin Thinning##
- Heavy Panting
- Recurring Skin Infections
Getting Your Dog Diagnosed
There is no test that will 100% determine if the dog has Cushing’s disease so the doctor will try to rule out other medical conditions to reach to a conclusion of Cushing’s disease.The doctor will diagnose cushing’s diseases in chronological order:
Order 1. The symptoms of Cushing’s disease match with many other diseases hence the doctor will ask for a diagnostic test which includes blood tests and urine tests. These tests will determine if the dog has UTI, urine dilution and issues with alkaline phosphatase count. If the above three analysis comes true then the doctor will ask for next order of tests.
Order 2. Doctor will order ACTH stimulation test and Low dose dexamethasone suppression (LDDS) test.
- ACTH stimulation test. In this test the functioning of adrenal glands is measured. A dose of hormone called ACTH is administered to the dog. This hormone should trigger the adrenal glands to produce cortisol. Two samples of blood are drawn from the dog, one sample before administering ACTH and one sample after. If blood level after ACTH shows below threshold cortisol level then adrenal glands are producing less cortisol and may lead to addison’s disease or if the cortisol level is found above threshold level then adrenal glands are producing more cortisol than required, hence can be a cause of Cushing’s disease.***
- Low dose dexamethasone suppression (LDDS) test There are two types of tests:
- “LOW DOSE” dexamethasone suppression test: The low dose dexamethasone suppression test can be used to screen for the presence of hyperadrenocorticism (Cushing’s disease) and in many cases, it will differentiate the type of Cushing’s disease that is present.†††
- “HIGH DOSE” dexamethasone suppression test. The high dose dexamethasone test is used when the patient has been confirmed with Cushing’s disease by means of the low dose test, but the low dose test has not clearly differentiated the type of Cushing’s disease that is present.‡‡‡
Both the low dose and the high dose dexamethasone suppression tests take 8 hours to complete and involve three blood samples.
The first sample is taken prior to the injection of dexamethasone, and the second and third samples are taken at 4 and 8 hours following the dexamethasone injection.
If the level of cortisol does not reduce as per the thresholds after 4 hrs and 8 hrs then the dog is having Cushin’s disease.
Order 3. If the tests in Order 2 are affirmative then the doctor will order ultrasound to check the tumour presence in adrenal glands and decide on the further course of treatment of dog.
Is There a Cure?
There is no cure for Cushing’s disease. The line of treatment is to avoid cortisol high level in blood and manage clinical symptoms of disease.
Is Cushing’s Disease Contagious?
No, Cushing’s disease is not contagious for other animals or humans.
What Are The Treatments?
If Pituitary Gland Related:
In case of pituitary gland tumour is benign then the doctors will try to treat the condition with the medicines. If the tumour is benign then the prognosis is generally positive but if the tumor is malignant then the prognosis is generally poor.
If Adrenal Gland Related:’
In case of adrenal gland tumour is benign then the doctors will try do a surgery and remove the tumour. If successful, your dog can lead a healthy life without any medications. If the tumour is malignant then the doctor will treat the condition with medicines. With the help of medicines, the dog can live a normal and healthy life but the treatment will have te be continued throughout life.
If Iatrogenic Type:
Dog who have been given steroids due to some medical conditions can develop Cushing’s disease. Due to this reason vet will slowly withdraw steroids medical treatment but unfortunately, the underlying medical condition for which steroids were given will rise again.
The most common drug given for the treatment of Cushing’s disease is trilostane (Vetoryl). Mitotane (Lysodren) is an older drug that vets don’t prescribe much anymore.
For a pet parent, they will have to keep a close check on dog’s medical requirements like frequently the dog will need to get a blood test done and will often need to visit vets. Its a life long treatment but successful treatment for many.