This column was written by Sarah McElroy, DVM
Cushing's disease, or hyperadrenocorticism, is a syndrome resulting from excessive production of glucorticoid, the body's natural steroid hormone. This can result from a hormonally active tumor of the pituitary gland in the brain, or less commonly, a hormone producing tumor of one of the adrenal glands. The adrenal glands sit next to the kidneys and produce both glucocorticoids to help the body manage stress and regulate blood sugar, as well as mineralcorticoids to help regulate water and sodium balance.
Overproduction of glucocorticoids typically results in increased thirst and urination, increased appetite, excess fat, decreased muscle tone, and decreased immune response to infection. Affected dogs often develop an enlarged liver and "pot bellied" appearance. They have a thin hair coat and be more prone to skin infections. Because blood sugar metabolism is affected, they may be at increased risk of developing diabetes. This syndrome can also result in high blood pressure and increased risks of "clotting or "stroke". Rarely, blindness can result from the effects of this disease.
Initial diagnosis of hyperadrenocorticism involves a thorough history and physical exam, as well as basic bloodwork. Affected dogs often show an increased liver value called alkaline phosphatase, from excessive storage of fat and glycogen in the liver cells.The disease can be confirmed by an ACTH stimulation test (a baseline blood cortisol reading, followed by an injection of adrenal stimulating hormone, and a second blood cortisol level two hours later.) An abdominal ultrasound can be used to evaluate whether there is an adrenal gland mass present or if both adrenal glands are enlarged due to influence of the pituitary tumor.
Treatment most often involves suppressing cortisol production to lessen symptoms and improve quality of life. The most commonly used medication is trilostane, an oral medication that is usually well tolerated. Surgical removal of the adrenal tumor is an alternative for those cases that do not respond to meds.