"BG" Persky is a very cute, playful and rowdy eleven year old Boston Terrier. After being perfectly house-trained for eleven years, she began having urinary "accidents" in the house and drinking excessive amounts of water. Diseases like diabetes mellitus (sugar diabetes), diabetes insipidus (water diabetes), renal disease, and Cushings disease came to mind. A complete blood panel ruled out some of the possible diseases but it was highly suspicious for Cushings disease.
Cushings disease is an excessive secretion of cortisol (the body's internal cortisone) into the blood stream by the outer layers of the adrenal gland. The adrenal glands are two small glands near the kidneys. This disease, or syndrome, is caused by a tumor located either on the adrenal gland or in the pituitary gland at the base of the brain. If a dog was given too much cortisone for a prolonged period of time, either by injection or in pill form, the above signs can be produced. Symptoms of Cushings other than excessive drinking and urination are; hair loss, potbellied appearance, sores that do not heal, calcified areas of the skin, blackheads in the skin, and a ravenous appetite. "BG" exhibited all of these symptoms to a certain extent.
Normal blood levels of cortisol are maintained in the dog by a negative feedback mechanism. For example, if cortisol levels are too high, a message via pre-hormones is sent from the hypothalamus in the brainstem to the pituitary gland at the base of the brain to stop a message sent by a hormone to the adrenal gland to produce any more cortisol. Tumors on the pituitary gland or the adrenal gland interfere with the negative feedback mechanism allowing the adrenal to pour excess cortisol into the blood.
It takes one or more two- or three-step blood tests to screen for Cushings disease. Once the disease is diagnosed, more testing is required to locate the cause (a tumor on the adrenal gland or the pituitary gland). If the adrenal glands can be imaged by ultrasound, this is an accurate way of locating the tumor. If the tumor is on the adrenal gland, the gland must be removed surgically by an experienced surgeon. If the tumor is on the pituitary, the disease can be controlled medically by an experienced clinician.
Thankfully, "BG’s" tumor was on her pituitary gland. We started her on a medicine called Lysodren, or OPDDD, daily until her excessive drinking and her ravenous appetite were greatly diminished. At that point we put her on the daily dose of medicine only once a week creating a lifetime maintenance schedule for the medicine. Lysodren temporarily destroys the outer surface of the adrenal gland and stops it from pouring excessive cortisol into the bloodstream. This creates a situation where the pituitary tumor has no target organ (adrenal cortex) to work upon, and it may be reduced in size. However, if Lysodren is withdrawn completely, the adrenal’s outer layers will again produce an excess of cortisol. To test to see if the Cushings is under control, the beginning two-step blood test that actually screens for the disease can be utilized.
Little "BG" is doing very well on her medicine. We are very hopeful that it will extend her life at least a few more years.