Hyperadrenocorticism Due To Pituitary Gland Dysfunction In Dogs

The pituitary gland is located near the base of the brain in the center. This gland is responsible for the production of a variety of critical hormones that control and influence many areas of the body, even including other endocrine glands. For this reason it is often called a master gland. A variety of conditions can be caused by pituitary tumors or diseases because of the vast amount of hormones produced by that gland. Symptoms of illness depend on the area of the gland that is affected and the cause.

Cushing’s Disease In Dogs ( Hyperadrenocorticism)

Cushing’s disease, or hyperadrenocorticism, is a condition that is created by an excess of cortisol in the body. It is very common in dogs, but not usually seen in other species. Some breeds are more likely than others to be affected, such as Beagles, Miniature Poodles, Dachshunds, Boston Terriers, and Boxers. In 85 to 90 percent of cases the cause is a small, benign pituitary tumor. However, in 10 to 15 percent of cases a tumor of the actual adrenal gland is the cause of Cushing’s.

Cushing’s disease is most common in middle-aged and older dogs. Lethargy, a swollen belly, heat intolerance, lethargy, increased appetite, panting, weakness, bruising, hair loss, thin skin, and increased thirst and urination are common symptoms of the disease. In rare cases mineral deposits on the skin called calcinosis cutis can develop. These appear as small, thick dots on the abdomen.

It can often be difficult to diagnose Cushing’s disease due to frequent inconclusive and false-positive laboratory results, especially in dogs that already have other conditions. If this kind of reading occurs it may be necessary to retest the dog three to six months later. When Cushing’s is confirmed it is generally necessary to run further tests to determine the cause (whether it is a tumor of the pituitary gland or adrenal gland). X-rays, ultrasounds, and sometimes even more sophisticated diagnostic tools can be used to evaluate these glands, such as computed tomography (CT), or MRIs.

Mitotane, a medication that “forces” the adrenal glands to decrease coritsol production, is often used to treat Cushing’s disease. When this treatment is used it is important to monitor dogs for signs of insufficient cortisol levels. These symptoms can include diarrhea, reduced appetite, and vomiting. Tests are done to determine whether coritsol levels are low enough about seven to 10 days after treatment has been administered. In many cases treatment with mitotane is continued and blood tests are done every so often to make sure cortisol levels are consistent and within the proper range. It is not uncommon for consistently increasing doses of mitotane to be administered in order to keep the disease under control. Side effects of mitotane include lack of coordination, seizures, low blood sugar, weakness, loss of appetite, and vomiting. In some cases side effects can be minimized by splitting the daily dose of mitotane into two equal doses, usually given eight to 12 hours apart.

Mitotane, however, is not the only drug capable of treating Cushing’s in canines. Trilostane is also effective at treating the disease, particularly pituitary-dependent Cushing’s, and studies indicate that it may have fewer harmful effects. Unfortunately, trilostane is not currently available in the United States unless express special permission is granted by the Food and Drug Administration (FDA).

Surgical removal is sometimes an option if adrenal gland tumors exist. Sometimes radiation of the pituitary gland is possible, but it can often take months to see signs of disease resolution.

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