Cushing's Disease In Dogs
What Are the Common Signs of Cushing’s Disease in Dogs?
Like humans and many other animals, dogs produce the hormone cortisol in response to stress. When in balance, cortisol helps dogs fight infections, maintain blood sugar levels, and control weight. But too much cortisol in their systems, called hyperadrenocorticism, can cause damage and lead to a host of maladies, like lack of energy, increased thirst, increased urination, or a “potbelly” abdomen.
Read on to learn more about the causes of the hyperadrenocorticism – commonly referred to as Cushing’s disease or Cushing’s syndrome – how to diagnose it, and what treatments are available.
Common Causes of Cushing’s Disease
A disorder of the endocrine system, Cushing’s disease tends to arise in middle-aged and older dogs. It is nearly always caused by tumors affecting either the pituitary gland or the adrenal glands, though a third factor is sometimes responsible.
Pituitary-dependent hyperadrenocorticism (PDH) is the most common cause of Cushing’s disease in dogs, representing about 80 to 85 percent of cases. PDH is caused by a tumor in the pea-sized gland at the base of the brain called the pituitary gland. Most times these tumors are benign, but occasionally they will be malignant. Their presence leads to an overproduction of adrenocorticotropic hormone (ACTH) that, in turn, stimulates the adrenal glands to produce an abundance of cortisol.
Adrenal-dependent hyperadrenocorticism (ADH) occurs as the result of a benign or malignant tumor of one of the adrenal glands that sit on top of the kidneys. These tumors also lead to an overproduction of cortisol. Approximately 15 to 20 percent of dogs will be diagnosed with this type of hyperadrenocorticism. Adrenal tumors have about an equal chance of being benign or malignant.
Iatrogenic Cushing's disease, though much less common, creates an over-production of cortisol stemming from excessive high-dose or long-term use of (medically-prescribed) oral or injectable steroids like prednisone. Corticosteroid medications used to treat allergies, reduce inflammation, or address autoimmune disorders tend to serve as the culprits.
Symptoms
Regardless of the underlying cause, the clinical signs of hyperadrenocorticism are fairly consistent. Thirst, urination, and an increase in appetite are the most common symptoms.
Many dogs with the disease will develop a “potbellied” or bloated appearance. This is due to an increase of fat around their abdominal organs and skin laxity of the abdomen as organs get heavier. Panting, lethargy, recurring skin infections, and hyperpigmentation (dark spots) are also signs.
Not every dog will present with every symptom, and some of these symptoms are associated with other ailments, so a proper diagnosis is important. Here are some things to look for:
Diagnosis
For a proper diagnosis, your veterinarian will take a comprehensive health history and do a direct physical examination of your pet. Often, basic blood tests will be recommended, to assess your pet’s overall health. If Cushing’s disease is still suspected as the cause of your dog’s symptoms, the vet will likely order one or more of the following tests:
Urinalysis
The urine can be tested to measure the cortisol to creatinine ratio to determine if it falls within normal ranges. If the ratio is high, further tests will be conducted as several conditions can lead to this result.
Testing will also detect diluted urine or the presence of a urinary tract infection, both of which are commonly found in dogs with Cushing’s disease.
Blood Tests
The Low-dose Dexamethasone Suppression Test (LDDST) is a common method for assessing your dog’s cortisol levels. Your dog’s blood is drawn to assess his or her baseline cortisol level, and then a small amount of dexamethasone is administered by injection. Blood cortisol levels are then measured four and eight hours afterward. Normally, dexamethasone has the net effect of suppressing cortisol secretions. If your dog has Cushing’s disease, the cortisol will not have been suppressed.
Similar to the LDDST, your vet may do an ACTH Stimulation Test to evaluate how well his or her adrenal glands work in response to an injection of the ACTH hormone. Blood samples are taken before and after the ACTH is administered to determine the glands’ impact on cortisol production.
Blood may also be tested for alkaline phosphatase enzymes, which can be elevated if adrenal-dependent hyperadrenocorticism is to blame.
Imaging
Abdominal ultrasound imaging may be used to help your veterinarian determine if there is a tumor on your dog’s adrenal glands. In some cases, x-rays can be useful to determine if a tumor has spread or is malignant.
No single diagnostic test is definitive for Cushing’s syndrome, but the tests above will help narrow down whether PDH or ADH is at play.
Treatment & Prognosis
Treatment will depend on the type of hyperadrenocorticism that is present in your pet.
Pituitary Tumors. PDH is by far the most common form of Cushing’s disease and is usually treated with medications. If your pet’s symptoms are not severe, treatment may be postponed, though you’ll need to continue to monitor your pet closely. Treatment generally starts when symptoms become more severe and usually comes in the form of medication.
If the tumor is not impacting brain function and the adrenal gland can be controlled through medication, many dogs can live normal lives, though they will require ongoing supervision. If the tumor is large or begins to grow, your dog may show signs of neurological distress, and the prognosis is less optimistic.
Adrenal Tumors. When a dog is diagnosed with an adrenal tumor, further imaging (e.g., MRI or CT scan) may be used to assess whether the tumor has spread. These tumors can be removed in some cases, or they can be treated with medication to alleviate the symptoms of Cushing’s disease. If the entire tumor is successfully removed (and is not malignant), your dog has a good chance of recovering fully. If the tumor is malignant, surgery may slow the progression, but the tumor could return. If surgery is not an option, dogs with adrenal tumors can often have a good quality of life when treated with medication.
Steroid Medication Overuse. Treatment for Cushing’s syndrome that develops from extended or overuse of steroids can be treated fairly easily, however other complications may arise. Dogs should be weaned off of these medications slowly while under the care of a veterinarian. Discontinuing them too quickly can lead to an adrenal crisis, called Addisonian crisis, which is a life-threatening condition.
Unfortunately, discontinuing the use of corticosteroids will likely result in the return of the condition that was being treated by them in the first place.
Not Sure What’s Going On with Your Dog?
Behaviors like panting, appetite changes and skin irritations have dozens of causes. If you’re not sure what’s going on with your pet, please make an appointment with us at Evergreen Animal Clinic, and we’ll get to the bottom of it!
Like humans and many other animals, dogs produce the hormone cortisol in response to stress. When in balance, cortisol helps dogs fight infections, maintain blood sugar levels, and control weight. But too much cortisol in their systems, called hyperadrenocorticism, can cause damage and lead to a host of maladies, like lack of energy, increased thirst, increased urination, or a “potbelly” abdomen.
Read on to learn more about the causes of the hyperadrenocorticism – commonly referred to as Cushing’s disease or Cushing’s syndrome – how to diagnose it, and what treatments are available.
Common Causes of Cushing’s Disease
A disorder of the endocrine system, Cushing’s disease tends to arise in middle-aged and older dogs. It is nearly always caused by tumors affecting either the pituitary gland or the adrenal glands, though a third factor is sometimes responsible.
Pituitary-dependent hyperadrenocorticism (PDH) is the most common cause of Cushing’s disease in dogs, representing about 80 to 85 percent of cases. PDH is caused by a tumor in the pea-sized gland at the base of the brain called the pituitary gland. Most times these tumors are benign, but occasionally they will be malignant. Their presence leads to an overproduction of adrenocorticotropic hormone (ACTH) that, in turn, stimulates the adrenal glands to produce an abundance of cortisol.
Adrenal-dependent hyperadrenocorticism (ADH) occurs as the result of a benign or malignant tumor of one of the adrenal glands that sit on top of the kidneys. These tumors also lead to an overproduction of cortisol. Approximately 15 to 20 percent of dogs will be diagnosed with this type of hyperadrenocorticism. Adrenal tumors have about an equal chance of being benign or malignant.
Iatrogenic Cushing's disease, though much less common, creates an over-production of cortisol stemming from excessive high-dose or long-term use of (medically-prescribed) oral or injectable steroids like prednisone. Corticosteroid medications used to treat allergies, reduce inflammation, or address autoimmune disorders tend to serve as the culprits.
Symptoms
Regardless of the underlying cause, the clinical signs of hyperadrenocorticism are fairly consistent. Thirst, urination, and an increase in appetite are the most common symptoms.
Many dogs with the disease will develop a “potbellied” or bloated appearance. This is due to an increase of fat around their abdominal organs and skin laxity of the abdomen as organs get heavier. Panting, lethargy, recurring skin infections, and hyperpigmentation (dark spots) are also signs.
Not every dog will present with every symptom, and some of these symptoms are associated with other ailments, so a proper diagnosis is important. Here are some things to look for:
- Increased thirst and urination
- Urinating at night or having indoor accidents
- Repeated bladder infections
- Increased hunger
- Increased panting
- Bloated or potbellied abdomen
- Persistent skin infections or poor skin healing
- Thin, hyperpigmented and/or scaly skin
- Obesity
- Fat pads on the neck and shoulders
- Loss of hair or slow-growing hair
- Lack of energy or muscle weakness
Diagnosis
For a proper diagnosis, your veterinarian will take a comprehensive health history and do a direct physical examination of your pet. Often, basic blood tests will be recommended, to assess your pet’s overall health. If Cushing’s disease is still suspected as the cause of your dog’s symptoms, the vet will likely order one or more of the following tests:
Urinalysis
The urine can be tested to measure the cortisol to creatinine ratio to determine if it falls within normal ranges. If the ratio is high, further tests will be conducted as several conditions can lead to this result.
Testing will also detect diluted urine or the presence of a urinary tract infection, both of which are commonly found in dogs with Cushing’s disease.
Blood Tests
The Low-dose Dexamethasone Suppression Test (LDDST) is a common method for assessing your dog’s cortisol levels. Your dog’s blood is drawn to assess his or her baseline cortisol level, and then a small amount of dexamethasone is administered by injection. Blood cortisol levels are then measured four and eight hours afterward. Normally, dexamethasone has the net effect of suppressing cortisol secretions. If your dog has Cushing’s disease, the cortisol will not have been suppressed.
Similar to the LDDST, your vet may do an ACTH Stimulation Test to evaluate how well his or her adrenal glands work in response to an injection of the ACTH hormone. Blood samples are taken before and after the ACTH is administered to determine the glands’ impact on cortisol production.
Blood may also be tested for alkaline phosphatase enzymes, which can be elevated if adrenal-dependent hyperadrenocorticism is to blame.
Imaging
Abdominal ultrasound imaging may be used to help your veterinarian determine if there is a tumor on your dog’s adrenal glands. In some cases, x-rays can be useful to determine if a tumor has spread or is malignant.
No single diagnostic test is definitive for Cushing’s syndrome, but the tests above will help narrow down whether PDH or ADH is at play.
Treatment & Prognosis
Treatment will depend on the type of hyperadrenocorticism that is present in your pet.
Pituitary Tumors. PDH is by far the most common form of Cushing’s disease and is usually treated with medications. If your pet’s symptoms are not severe, treatment may be postponed, though you’ll need to continue to monitor your pet closely. Treatment generally starts when symptoms become more severe and usually comes in the form of medication.
If the tumor is not impacting brain function and the adrenal gland can be controlled through medication, many dogs can live normal lives, though they will require ongoing supervision. If the tumor is large or begins to grow, your dog may show signs of neurological distress, and the prognosis is less optimistic.
Adrenal Tumors. When a dog is diagnosed with an adrenal tumor, further imaging (e.g., MRI or CT scan) may be used to assess whether the tumor has spread. These tumors can be removed in some cases, or they can be treated with medication to alleviate the symptoms of Cushing’s disease. If the entire tumor is successfully removed (and is not malignant), your dog has a good chance of recovering fully. If the tumor is malignant, surgery may slow the progression, but the tumor could return. If surgery is not an option, dogs with adrenal tumors can often have a good quality of life when treated with medication.
Steroid Medication Overuse. Treatment for Cushing’s syndrome that develops from extended or overuse of steroids can be treated fairly easily, however other complications may arise. Dogs should be weaned off of these medications slowly while under the care of a veterinarian. Discontinuing them too quickly can lead to an adrenal crisis, called Addisonian crisis, which is a life-threatening condition.
Unfortunately, discontinuing the use of corticosteroids will likely result in the return of the condition that was being treated by them in the first place.
Not Sure What’s Going On with Your Dog?
Behaviors like panting, appetite changes and skin irritations have dozens of causes. If you’re not sure what’s going on with your pet, please make an appointment with us at Evergreen Animal Clinic, and we’ll get to the bottom of it!
