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Cushing’s disease, or hyperadrenocorticism, occurs when the two small adrenal glands located near the kidneys produce too much cortisol (or glucocorticoid hormones). This process usually stems originally from the pituitary gland, located near the base of the brain, which produces adrenocorticotrpic hormone, also known as ACTH. “This hormone is released into the bloodstream and stimulates the body’s two adrenal glands, located near the kidneys, to secrete glucocorticoid (cortisone-like or cortisol) hormones into the bloodstream,” reports the KateConnick website.
Overexposure to the hormone, however, has a negative effect on the body.
“Cortisol is stored in the adrenal gland and is released in times of stress where it helps our bodies prepare for a ‘fight or flight’ situation,” reports Mar VistaVet. “It adjusts the metabolism to expect physical exertion by mobilizing fat and sugar stores and retaining sodium and water. It puts us in a state of ‘break down’ so that our stored resources can be used quickly. If the body is exposed to this hormone most of the time, however, instead of during short stressful periods only, the state of break down becomes debilitating.”
Because of the effect it has on certain functions, Cushing’s disease’s symptoms often mirror the normal aging process dogs go through. And because Cushing’s strikes primarily middle-aged to older dogs, it can sometimes be difficult for pet parents to notice an initial problem.
Some signs that your dog may have Cushing’s disease include:
- Increased water intake
- Increased appetite
- Incontinence or urination accidents
- Muscle atrophy
- Weight gain and/or pot-bellied appearance
- Coat loses its shine/becomes dull
- Difficulty climbing stairs or jumping on furniture
- New susceptibility to infections, such as skin ailments
- Hair loss
- Hair that is extremely slow to grow back after a clipping
- Thin skin
- Excessive panting
What Causes Cushing’s Disease?
There is more than one cause for Cushing’s, though most cases (about 80-85 percent by most estimates) fall into the pituitary-dependent category. Essentially, that means a small tumor begins growing on the pituitary gland, causing the chain-reaction of over-producing ACTH and then the excessive stimulation of adrenal glands, which leads to the over-production of cortisol.
In a smaller percentage of dogs, the tumor appears on the adrenal glands, causing an oversecretion of the glucocorticoids. In these cases, “there is very little or no production of ACTH from the pituitary gland and as a result the opposite adrenal gland is usually atrophied/small,” according to Mar Vista Animal Hospital.
The third cause stems from the overuse or high doses of steroids that have been prescribed by a veterinarian. “The pituitary gland perceives the high steroid levels yielded by the medication and does not send stimulation to the adrenal glands,” writes the MarVistaVet website. “In time, the adrenal glands atrophy and are not able to release cortisone on their own should they be required to do so.”
In these cases, the problem should correct itself once the dog is weaned from the medication.
How is Cushing’s Disease Diagnosed?
If you suspect your dog may have Cushing’s Disease, your veterinarian will run a series of tests that includes blood work, such as a complete blood count and blood chemistry panel, and a urinalysis. Thorough testing can help determine if Cushing’s disease is present and, depending on the tests, the type of Cushing’s disease—pituitary, adrenal or steroids.
“Routine blood analysis often shows that the pet has higher than normal levels of Alkaline Phosphatase (ALP), Alanine aminotransferase (ALT), cholesterol and blood glucose as well as very dilute urine,” reports 2ndchance.info.
If these results point to the possibility of Cushing’s, other tests can be performed, such as a low-dose dexamethasome suppression test, which can show a significant decrease in blood cortisol levels in most dogs without Cushing’s when the dog is tested eight hours after being given low doses of dexamethasone.
In an ACTH Stimulation Test, “a dose of ACTH is given to the patient,” Mar VistaVet writes. “If a larger than expected rise in cortisol levels is measured in two hours we may diagnose Cushing’s syndrome.”
Your vet may also recommend an ultrasound to examine the adrenal gland or an MRI to examine the pituitary gland, according to Petside.com.
Treating Cushing’s Disease
There are a few options when it comes to treating Cushing’s disease in dogs. If your veterinarian knows which kind of Cushing’s disease your dog has, that may factor into the course taken. If it’s an adrenal tumor, for instance, surgical removal might be an option, reports Pet Education. “There are several different forms of tumors that can invade the adrenal gland and their treatment will be based on the particular tumor type,” says the site.
If the tumor is malignant and caught in a timely manner, the veterinarian may elect to remove it to avoid risk of the cancer spreading. The problem here is that by the time Cushing’s disease is diagnosed, if the tumor is cancerous it may likely have already spread to other parts of the body. If that’s the case, then there’s really no use in removing the tumor. If it’s benign, though, the vet may decide to treat the condition with medication only.
Unfortunately, it is not possible to surgically remove a tumor from a pituitary gland, so medication will manage the disease.
“Pituitary tumors are not removed surgically because removing them is too risky and they are very small and do not usually grow any larger,” reports Dog-health-guide.org. “Instead, treatment focuses on managing the symptoms of the condition. Radiation can be used to shrink the tumors further, but this is quite costly and most dog owners opt against it.”
Because surgery is not possible for pituitary tumors, which are the most common kind, and medication typically works for both types of tumors, cancer cases sometimes excepted, medication is typically a good option for both types of tumors.
The important word when treating Cushing’s is management. There is currently no cure for Cushing’s disease (or prevention) but ongoing treatment is possible.
“Although Cushing’s is typically a lifelong condition, the disease usually can be managed with medications,” reports the FDA.gov site.
In the beginning stages of treatment, the dog will likely need frequent blood tests and then every few months after that, depending on how the dog is responding to treatment, says the FDA.
After beginning treatment, the excessive drinking and eating will likely correct itself quickly; hair should start to grow back, although this process may take longer.
The prognosis for dogs after treatment depends on the dog’s health and age, the tumor size, and also the level of care. “The outlook for surgical treatment of adrenal gland tumors is fairly good, provided that the animal survives the surgery and the period immediately after,” reports Pets.ca. “As a rule, dogs with benign adrenal gland tumors live longer than dogs with malignant tumors. Metastasis, or spread of a malignant tumor, makes for a worse prognosis. Such animals can be treated successfully with medication to help keep symptoms under control after surgery.”
The most important thing is to ensure your dog receives the proper medical treatment tailored to age and health, and type of Cushing’s. If left untreated, the disease will progress. And because excess cortisol is immunosuppressive, it leaves dogs open to infections and predisposes them to hypothyroidism, pancreatitis, diabetes, seizures, hypertension, congestive heart failure, blood clots, and liver and kidney failure, according to KateConnick.com.
Treatment can improve a dog’s quality of life immeasurably and your dog can live comfortably with the disease under control for years.