By Matthew Kearns, DVM
When a client brings their pet into my office and states that they are drinking more and urinating in the house a few common diseases come to mind. One prominently on the list is Cushing’s disease. Cushing’s disease is caused by hyperadrenocorticism, or an overactive adrenal gland. The adrenal glands are two small glands that sit in front of the kidneys and are responsible for homeostasis. Homeostasis, as described to me back in veterinary school, is “keeping our bodies even in an uneven world.”
The adrenal glands produce hormones that regulate blood pressure, control electrolyte balance, produce precursors to the sex hormones (estrogen, testosterone), and control metabolism and immune function. The portion of the adrenal gland that causes Cushing’s disease is called the zona fasciculata. This portion of the gland is responsible for producing cortisol, or the body’s natural cortisone.
Normal concentration of cortisol is imperative in the metabolism of carbohydrates, proteins and fats. Cortisol also plays a crucial role in the immune system by acting as a natural anti-inflammatory. The overproduction of cortisol leads to the symptoms associated with Cushing’s disease. These symptoms include increased thirst and urination, increased appetite, hair loss along the back, abdominal distension, muscle weakness, increased risk of common infections associated with suppression of the immune system such as skin, or urinary tract infections.
Cushing’s disease is much more common in dogs than cats. Any dog can develop Cushing’s disease but breeds more at risk are Poodles, Boston Terriers, Pomeranians, Maltese, Beagles, Dachshunds, and Cocker Spaniels to name a few.
Diagnosis of Cushing’s disease is made with bloodwork. Screening tests will usually reveal an increase in certain liver enzymes. There may be other changes but the hallmark is an elevation in liver enzymes. The definitive diagnosis is made with what is termed an “adrenal stress test.” Basically, a baseline sample of blood is taken, followed by medication to stress the adrenal glands. Additional samples are taken to measure how the adrenal glands respond. Additional testing such as ultrasound or MRI are recommended but not required for diagnosis.
Once a diagnosis of Cushing’s disease is made medication is dispensed. Older medications such as mitotane or ketoconazole are still used but have more side effects. A newer medication called trilostane is much safer. Follow up bloodwork is used to monitor treatment and either adjust dosages, or consider other medications.
If your pet (especially your dog) is drinking more and urinating more bring them to your veterinarian right away. Cushing’s may be the cause and early diagnosis and intervention is always most successful.
Dr. Kearns practices veterinary medicine from his Port Jefferson office and is pictured with his son Matthew and his dog Jasmine. Have a question for the vet? Email it to [email protected] and see his answer in an upcoming column.