Canine Cushing's disease
Canine Cushing’s disease, also known as hyperadrenocorticism, is a common endocrine disorder. Endocrine disorders are internal conditions caused by hormonal balances. Cushing’s disease is caused by abnormal levels of cortisol, usually a result of an adrenal tumor or pituitary tumor. A potbellied appearance is one giveaway of Cushing’s disease. Other signs include:
- Excessive thirst
- Increased urination
- Excessive appetite
- Recurrent skin infections
- Skin calcification (calcinosis cutis)
- Muscle wasting
- Elevated liver values, particularly alkaline phosphatase (ALP)
Type's of Cushing's disease
There are three common forms of Cushing’s disease. The most common is pituitary-dependent Cushing’s disease (80% of cases), in which a small, benign tumor of the pituitary gland produces excess ACTH hormone, which then stimulates the adrenal glands to produce excess cortisol. The second common form is adrenal-dependent Cushing’s disease, in which a tumor in the adrenal gland’s stimulates excessive cortisol production directly. The third form is Iatrogenic Cushing’s syndrome, which derives from the administration of cortisol as a medication.
Diagnosing Cushing's disease
To diagnose Cushing’s disease, we often recommend a blood test called a low dose dexamethasone suppression test (LDDST), which takes 8 hours to complete. Other diagnostic tests include an ACTH stimulation test (another blood test) and an abdominal ultrasound.
Treating Cushing's disease
If possible, surgical removal of the tumor can be considered. If surgery is not possible, the general treatment of choice for both pituitary- and adrenal-dependent Cushing’s disease is a medication called Vetoryl (trilostane). Vetoryl decreases the production of cortisol, which is the main contributor to Cushing’s disease. When using this medication, initial close monitoring is critical to the treatment to assure your pet is tolerating it well and that cortisol levels have been lowered to a specific target range. If cortisol levels are reduced too much, hypocortisolemia (Addison’s disease) can be caused, which can be associated with weakness and gastrointestinal side effects.
Many patients with Cushing’s disease suffer from skin and ear infections secondary to immunosuppression (excessive cortisol lowering the immune system). In these patients, oral antibiotics may be indicated. Additionally, topical therapy is essential to the recovery process as well. Appropriate and consistent topical therapy, such as using MiconhexTriz shampoo twice weekly, medicated spray, mousse, or wipes twice daily on non-bathing days, can effectively minimize any incidence of infection.
In patients with calcinosis cutis (calcium deposits in the skin), DMSO is a topical treatment that can chelate calcium from the skin. Since DMSO is a carcinogen (a substance that can potentially cause cancer), this treatment can be administered after calcinosis cutis becomes more localized, instead of smearing it all over the patients’ bodies. Oral doxycycline or minocycline are antibiotics that can be used to chelate calcium in the blood. If these antibiotics are tolerated, they are usually given to pets for 8 weeks. Lastly, Phovia therapy is a non-invasive fluorescent light biomodulation therapy that can help speed up the healing process of the skin and can help fight infection.
Prognosis
When Cushing’s disease is diagnosed and treated, it can usually be managed well. Most symptoms of Cushing’s disease will improve in a matter of weeks to months.
Unfortunately, calcinosis cutis is one of those conditions that can worse before it gets better. Even after Cushing’s disease is controlled, calcinosis cutis can take about 6 months to completely go away. If the calcium deposition has organized into bone, then certain areas of the skin may remain calcified. However, if the affected area remains focal, then the outlooks is still usually good.
Since Cushing’s disease is caused by a tumor, it has the potential to shorten pets’ life spans, but this is only a possibility that does not apply to every case. Fortunately, the earlier Cushing’s disease can be diagnosed, the earlier it can be treated, and the better the prognosis.
