Cushing̵7;s disease in dogs is a condition marked by an increased level of glucocorticoid hormones over weeks or months. The glucocorticoid hormone, including cortisol, affects the metabolism of carbohydrates. Middle-aged and older dogs may suffer from this serious muscular disorder that can lead to discomfort and even death if untreated. Cushing̵7;s disease affects the beagle, Boston terrier, boxer, dachshund, German shepherd, golden retriever, Labrador retriever, poodle and Yorkshire terrier.
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Causes
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The pituitary gland and adrenal glands need to function properly to maintain the correct level of glucocorticoid hormones. Tumors on the pituitary gland or adrenal gland cause spontaneous Cushing̵7;s disease. Tumors of the pituitary glands cause 85 percent of spontaneous Cushing̵7;s disease and is more prevalent in smaller dog breeds under 45 lbs. Tumors of adrenal glands cause 15 percent of spontaneous Cushing̵7;s disease, and accounts for 50 percent cases in dogs under 45 lbs.
The pituitary gland at the base of the brain controls the cortex layer that produces and releases corticosteroids. Two types of corticosteroids regulate electrolyte concentrations and suppress the immune system and reduce inflammation.
The adrenal glands above each kidney produce cortisol. Tumor cells from the pituitary gland cause overproduction of the secreted hormone adrenocorticotropic (ACTH) that stimulates the adrenal cortex to overproduce cortisol. The imbalance of cortisol poisons the dog̵7;s body.
Medications that contain corticosteroids to reduce inflammation may also cause Cushing̵7;s disease.
Cushing's disease may cause other health problems such as diabetes mellitus, congestive heart failure, seizures and infections.
Symptoms
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A dog may indicate symptoms up to six years prior to a diagnosis. Symptoms may include bloating, loss of bladder control, increased urination, calcified skin lumps, delayed wound healing, diabetes, dull coat, hair loss, increased water drinking, excessive panting, seizures, muscle weakness, excessive appetite and hanging abdomen. Advanced cases show rigidness of extremities that causes the dog to walk stiffly.
Diagnosis
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Diagnosis procedures that indicate abnormalities, but fail to provide a definitive diagnosis, may include complete blood count, blood chemistry panel, urinalysis and abdominal ultrasound. A low dose dexamethasone test indicates the dog̵7;s blood cortisol levels.
Treatment
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Treatment includes surgical removal of these tumors that affect the production level of hormones. Drugs include Anipryl (L-deprenyl hydrochloride) to alleviate symptoms caused by pituitary problems and mitotane (brand name: Lysodren) to destroy cells of the adrenal cortex and to suppress corticosteroid production.
Morphine
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A veterinarian can prescribe morphine to alleviate pain. As an extra-label drug, morphine is used in a different way from what the label describes. Please note that morphine will not cure Cushing's disease. Derived from the opium plant, morphine is available as an injection, oral solution, oral tablet and rectal suppository. Dogs may vomit or defecate following an injection. Owners should be aware that this narcotic requires frequent doses.
Morphine may interact with antihistamines, anesthetics, monoamine oxidase inhibitors and tranquillizers. Dogs should not receive morphine if they have kidney disease, liver disease, hyperactivity, underactive thyroid gland, toxin-induced diarrhea or scorpion bites of Addison̵7;s disease.
Adverse effects include nausea, slowed intestinal movement, constipation, low blood pressure, seizure, slowed heart rate, slowed breathing, restlessness, behavioral changes and vomiting. Owners should be aware that the most profound adverse effects include suppression of breathing and sedation.
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