Cushing’s Disease (Hyperadrenocorticism) in Dogs
Hyperadrenocorticism, commonly known as Cushing’s disease, is an endocrine (hormonal) disorder that is most common in middle- to older-aged dogs. Cushing’s disease is a serious medical condition. It is caused by excess cortisol levels, which can affect multiple organ systems and lead to potentially dangerous complications.
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Hyperadrenocorticism can be an insidious disease. If your dog is predisposed to developing Cushing’s disease, understanding the symptoms, risks, and long-term management responsibilities associated with the condition will help you prepare for a possible diagnosis.
Symptoms of Cushing’s disease in dogs may vary from dog to dog. Like other endocrine disorders, Cushing’s disease can be challenging to detect until the condition is well underway, and many of the symptoms may initially seem unrelated.
Hyperadrenocorticism affects multiple organ systems, which creates widespread symptoms, including changes in behavior, appearance, and disease resistance. You may notice that your dog appears more hungry and thirsty than usual or has difficulty handling heat. Dogs with Cushing’s disease are also more likely to contract infections like urinary tract infections and bacterial skin infections, as the virus suppresses their immune systems.
One of the more distinctive signs of Cushing’s disease in dogs as the condition progresses is a pot-bellied appearance, which results from enlargement of the liver and a redistribution of body fat. Hair loss is also common, especially on the abdomen.
Common symptoms of Cushing’s disease:
Muscle weakness due to muscle atrophy
Increased thirst and increased urination
Increased incidence of urinary tract infections
Alopecia (hair loss)
Increased risk of bacterial skin infections
Calcinosis cutis (hardening of the nose and pads)
Cushing’s disease is caused by dysfunction in either the pituitary or adrenal glands; that dysfunction, in turn, is caused by tumors. The affected glands produce excessive levels of cortisol steroids, which disrupt normal function and can affect multiple organ systems.
Pituitary gland tumor
Adrenal gland tumor
Pituitary-dependent hyperadrenocorticism (PDH) is the most common type of Cushing’s disease in dogs. Tumors on the pituitary gland cause 85% of canine hyperadrenocorticism cases. The pituitary gland is located in the brain, and is responsible for secreting hormones that regulate body function. Tumors on the adrenal gland, which is located in the abdomen and is also responsible for secreting essential hormones like adrenaline, are less common but occur in approximately 15% of cases.
Certain breeds of dogs are predisposed to developing Cushing’s disease. Hyperadrenocorticism is especially common in Dachshunds, Miniature Poodles, Cocker Spaniels, and Beagles, and females of these breeds are at an even higher risk.
Diagnosing Cushing’s disease in dogs requires patience, as no one test can definitively diagnose the condition.
In most cases, veterinarians who suspect Cushing’s disease begin with initial blood work tests like CBC, chemistry panels, or a urinalysis. Once they receive the results, they will look for evidence of Cushing’s disease, like elevated liver enzymes, decreased BUN levels, and high cholesterol.
Next, your veterinarian may recommend an abdominal ultrasound to assess organs like the liver, kidney, and adrenal glands; in some cases, your veterinarian may even be able to see an adrenal gland tumor. Measuring the urine’s cortisol-to-creatinine ratios can also point toward Cushing’s disease, but there are other causes of elevated cortisol-to-creatinine ratios besides Cushing’s disease which will need to be ruled out.
The diagnostic tests of choice for diagnosing Cushing’s disease are a low-dose dexamethasone suppression test (LDDST) and an ACTH stimulation test. Sometimes only one of these tests is needed, while at other times it is necessary to perform both tests to obtain a definitive diagnosis.
In some cases, an additional diagnostic called a high-dose dexamethasone suppression test (HDDST) is necessary. This test is particularly helpful in differentiating between pituitary-dependent and adrenal-dependent disease. This distinction is vital for treatment. However, this test requires patients to spend at least eight hours in the hospital and can be expensive, which is one of the reasons it is not usually taken as a first step in the diagnostic process.
Your veterinarian may also recommend additional diagnostic tests to rule out other conditions and to diagnose any underlying conditions or infections.
Pituitary-dependent hyperadrenocorticism (PDH), which is the most common form, is usually treated with medications like mitotane or trilostane. These medications help lower cortisol levels and reduce the symptoms of Cushing’s disease. Radiation therapy of pituitary tumors is also sometimes an option but is considered less often, and the location of the pituitary gland in the brain makes surgical approaches too risky.
Adrenal tumors, on the other hand, are located in the abdomen and are therefore easier to target. Adrenal tumors also have a higher rate of malignancy. This, combined with their location, makes surgical removal a more attractive option. However, mitotane or trilostane is also effective at treating adrenal-dependent hyperadrenocorticism.
Treating the symptoms of hyperadrenocorticism may require additional treatment steps. For example, bacterial skin infections and urinary tract infections may require antibiotics, and your veterinarian may recommend additional medications or protocols for other symptoms or complications, like high blood pressure.
Is There a Cure for Cushing’s Disease?
There is no cure for Cushing’s disease. Instead, the goal of treatment for this disease is managing the clinical signs and decreasing the side effects of elevated cortisol in the bloodstream.
Is Cushing’s Disease Contagious for Humans or Other Pets?
No, Cushing’s disease is not contagious for other animals or humans.
What Is the Cost of Treating Cushing’s Disease?
The cost of the initial diagnosis and treatment for Cushing’s disease may range from several hundred dollars to over a thousand dollars, depending on the case. If you have financial concerns, be sure to talk with your veterinarian about the cost of treating Cushing’s disease before beginning treatment.
Continuing to treat Cushing’s disease is a long-term commitment. Dogs with Cushing’s disease will require daily medications as well as routine blood work and diagnostic testing. The medications range in price, but over time can add up to a significant amount. Dogs with Cushing’s disease are also more likely to develop other conditions, like infections and diabetes. Treatment costs for these conditions also vary.
Treating your dog for Cushing’s disease requires intensive management, and you should expect frequent veterinary visits to monitor your dog’s condition, especially in the first few months after diagnosis. If you have opted to treat your dog’s Cushing’s disease with a medication like trilostane, your veterinarian will most likely recommend regular ACTH stimulation tests to determine the efficacy of your dog’s medication and may adjust the dosage accordingly. Regular blood work to ensure your dog’s kidney and liver are functioning normally is also recommended, as well as running a urinalysis to check for urinary tract infections.
The initial treatment requires the most intensive management. Veterinarians recommend ACTH stimulation tests every few weeks until dogs are stabilized, then follow-up tests every six months to a year following the initial treatment phase. Dogs with adrenal tumors that undergo adrenalectomies to remove the tumor may need supplemental medication and additional monitoring.
Cushing’s disease progresses slowly. Without treatment, dogs develop higher risks of high blood pressure; pulmonary thromboembolism, which can result in sudden death; congestive heart failure; neurological symptoms; blindness; and myopathy. Dogs with Cushing’s disease are also more likely to develop other conditions, like diabetes.
Cushing’s disease cannot be prevented. However, understanding the treatment options, costs, and necessary management steps can prepare you for the road ahead.
Is There a Vaccine for Cushing’s Disease?
There is no vaccine for Cushing’s disease, as hyperadrenocorticism is an autoimmune condition, not an infectious one.
Hyperadrenocorticism, or Cushing’s disease, is a hormonal disorder where the body produces excess levels of cortisol. It’s most often caused by a tumor on the pituitary gland or the adrenal gland. It results in a variety of symptoms that may seem unconnected at first. One of the more distinctive signs is a pot-bellied appearance. While it’s not preventable, catching the disease early can improve your dog’s prognosis.