Cushing disease|hyperadrenocorticism|Whitney Veterinary Hospital

Hyperadrenocorticism is a disorder caused by the excessive production of cortisol by the adrenal cortex. The common term for hyperadrenocorticism is Cushing disease.

Cushings disease can be caused by a pituitary problem, an adrenal problem, or an overdose or chronic usage of steroids.

Approximately 85 to 90% of hyperadrenocorticism cases are due to an over-production of ACTH (a hormone) by the pituitary gland. The pituitary gland is located in the brain, behind the eyes. This gland tells the adrenal glands how much cortisol to make. It also tells them when to stop. Over-stimulation of the pituitary gland results in hyperplasia of the adrenal glands. Hyperplasia means enlargement.

The remaining ten to 15% of cases are caused by a tumor of the adrenal gland, with more than 50% of these being malignant. In cases of overdose or chronic use of the glucocorticoids (in other words steroids, iatrogenic), the disease can occur. Iatrogenic means human induced.

Cushing disease is a multi-systemic disorder. That means that many different organs are affected by the overproduction of cortisol. Most notably, symptoms will occur in the skin and in the urinary tract.:

A thinning of the skin
A pot bellied appearance
A generalized pinkness can be seen
Increased drinking and urinating is also noticed
It is not uncommon for people to report that their dog also has a ravenous appetite

poodles
dachshund
Boston terriers
boxers
beagles

This disease is generally seen in older animals, but can be seen in animals as young as a year of age.

Because this disease affects many organs, the numbers of symptoms that can be seen vary widely. They can include :

excessive drinking and urination
increased hunger
pendulous abdomen (pot belly)
enlarged liver
hair loss
lethargy
muscular weakness
muscle atrophy
increased panting and other symptoms

It's important to differentiate this disease from other causes of the above symptoms. Diseases to rule out include:

hypothyroidism
diabetes mellitus
liver disease
other causes of increased drinking and urination such as infection

Your veterinarian will perform tests including a full blood panel, urinalysis, and perhaps some special tests. Special tests include:

an ACTH response test
a low dose dexamethasone suppression test
a urine cortisol:creatinine ratio
other hormonal tests

Sometimes abdominal radiographic (x-rays) and ultrasound may be used to help us determine if we have a tumor in the abdomen involving the adrenal gland. Ultrasound is often more utilized than x-ray.

The treatment of this disease depends entirely on the severity of clinical signs, the patients overall health, and any other complicating factors that may be involved.

For example, Cushing disease severely complicates diabetes mellitus, or sugar diabetes.

If your pet has diabetes, treatment of Cushing disease becomes imperative. In some cases, the symptoms are very mild and your pet is only mildly affected. In these cases, no treatment may be needed.

The treatment for this disease involves medication in most cases. The primary medication used is mitotane, (o,p'-DDD)™. This medication selectively destroys part of the adrenal gland. Severe side effects can be found, and include complete destruction of the adrenal gland. If this occurs, Addison's disease will result. (For more information on Addison's disease please see our handout.) In the case of adrenal tumor, surgery may be needed, although this is rare.

There has been some discussion of the use of a drug called l'Deprenyl or Anipryl™ for the treatment of Cushing disease. Controversy exists as to whether or not this is helpful. It has been reported that anywhere from zero to 75% of dogs may have a good response. If your pet has a very mild case of Cushing disease, this may be an option. This drug has minimal side effects, but may not help your pet. In rare cases other drugs may be chosen. If any other drugs are chosen, your veterinarian will explain in detail the reason in the usage of that drug.

Mitotane, or o,p'-DDD, is the most commonly used drug. The side effects of this drug, which are not uncommon, include:

lethargy
weakness
loss of appetite
vomiting and diarrhea
and sometimes a loss of the adrenal gland

The higher the dosage is, the more likely that side effects will be seen. Your veterinarian will advise you on the proper use of mitotane. Please use it exactly as directed. If your pet is experiencing any side effect from this drug, please discontinue the medication and contact your veterinarian immediately.

Treatment must be monitored closely. Seven to ten days after the beginning of your medication, a repeat a low dose dexamethasone test may be performed. This is to help ensure the exact dosage of your pet's medication and treatment of this disease. Lack of monitoring can result in serious and life threatening side effects. Once regulated most pets do exceedingly well, but do require semi-annual rechecks.

Without treatment, hyperadrenocorticism or Cushing disease is generally a progressive disorder with a guarded to poor outlook. The treatment generally results in a good prognosis.

If your pet has an adrenal carcinoma, the outlook is very poor. Adrenal carcinomas,(tumors of the adrenal glands), tend to invade other organs making them difficult if not impossible to remove. If your pet is been diagnosed with an adrenal carcinoma, your veterinarian will advise you on the appropriate treatment.

Because Cushings disease affects so many organs, the disease may be contributing to the difficulty in treating other diseases being regulated. An example of this is that of diabetes mellitus, or sugar diabetes. Pets with diabetes and Cushing's disease have incredibly high blood sugar values and are difficult to regulate. In this case, treatment of the Cushing disease is imperative in order to assure the diabetes can be treated.

If you have any questions regarding Cushing disease, or any other diseases, Please do not hesitate to contact us at 309-685-4707 We will be happy to answer any questions that you may have and ensure that your pet has the best of health.

Cushing disease - hyperadrenocorticism - in Dogs!

by Dr. N.J.Hayes, DVM