Diagnosis No single laboratory test definitively identifies Cushing's syndrome, and the disorder should not be diagnosed solely on the basis of laboratory tests. Your veterinarian should also consider the medical history and physical examination findings when establishing a diagnosis and determining the appropriate laboratory tests to perform. Several of the following diagnostic tests may be required for the diagnosis of Cushing's syndrome:
Complete blood count (CBC)
Biochemical profile
Urinalysis and bacterial culture of the urine
Blood pressure measurement
Radiographs (X-rays) of the chest and abdomen
Urine cortisol-to-creatinine ratio
Abdominal ultrasound examination
ACTH stimulation test
Low dose dexamethasone suppression test
Measurement of blood ACTH concentration
High dose dexamethasone suppression test
CT (computed tomography) or MRI (magnetic resonance imaging) scans of the brain or abdomen
Treatment
Several approaches may be used to treat dogs with Cushing's syndrome. Treatment options depend primarily on whether the Cushing's syndrome is pituitary-dependent or adrenal-dependent.
Pituitary-dependent Hyperadrenocorticism
Medical therapy with o,p'-DDD (mitotane or Lysodren®) causes selective destruction of the cortisone-producing portions of the adrenal gland and limits the ability of the gland to produce cortisone.
Ketoconazole (Nizoral®) is an anti-fungal drug that also blocks the synthesis of cortisone in the adrenal gland. It is sometimes used to treat hyperadrenocorticism.
L-Deprenyl increases dopamine concentration in the brain. Increased dopamine concentration may decrease cortisone production in the adrenal glands. The use of L-deprenyl to treat Cushing's syndrome in the dog is very controversial. Some veterinarians believe it has a beneficial clinical effect whereas others have found no evidence of an effect despite extensive laboratory testing of treated dogs.
Adrenal-dependent Hyperadrenocorticism
Surgical removal of an adrenal tumor is a difficult, but potentially curative surgery. Surgery is not indicated if the adrenal tumor has invaded adjacent vessels and organs or spread distantly (metastasized).
Adrenal tumors also can be treated medically with mitotane or ketoconazole. Medical therapy may be the only choice if the tumor has invaded locally or spread distantly.
Home Care
Follow your veterinarian's instructions very closely when administrating medications, especially in the induction phase when using mitotane. Observe your dog for weakness, vomiting, diarrhea, loss of appetite or change in attitude. You should also observe your dog for improvement or worsening of clinical signs.
Follow-up with your veterinarian for routine re-evaluation of blood tests so as to maximize the chance for successful treatment.
Preventative Care
There is no known way to prevent Cushing's syndrome. However, some preventative measures may lead to earlier diagnosis and potentially more effective treatment:
As your dog gets older, more frequent routine visits to the veterinarian may identify early symptoms of the disease.
Routine performance of blood tests (complete blood count, biochemical profile, urinalysis) in older dogs may identify laboratory abnormalities associated with hyperadrenocorticism.
Monitor your dog for any changes in behavior or attitude, especially increased water consumption, increased urinations, and increased appetite.
