What Is Addison’s Disease?
Addison’s disease, scientifically known as hypoadrenocorticism, is a disease with serious consequences for dogs, although fortunately with proper treatment, dogs diagnosed with Addison's disease are expected to have normal lifespans. Addison’s disease occurs when the adrenal glands fail to produce the hormones that they are supposed to for the body. The most important hormones produced by the adrenal glands are steroids, particularly aldosterone and cortisol. These steroids play a large role in regulating your dog’s internal organs and body systems. Without them, your dog’s body deteriorates, leading to serious complications and death.
Causes of Addison’s Disease in Dogs
In most cases, the cause of Addison’s disease in dogs is unknown. Veterinarians suspect that most of these cases result from an autoimmune process. Addison’s disease can also be caused by destruction of the adrenal gland, either by a metastatic tumor, hemorrhage, infarction, granulomatous disease, adrenolytic agents like the drug mitotane, or a drug like trilostane that inhibits adrenal enzymes.
When something interferes with the adrenal gland, the body is no longer able to produce glucocorticoids and mineralocorticoids, specifically aldosterone and cortisol. This leads to a wide range of symptoms and in acute cases of Addison’s disease, death.
Scientists may not know what exactly causes Addison’s disease, but any dog can develop Addison’s disease, whether a purebred or mixed breed dog. There are, however, some breeds that appear to be predisposed to the disease:
· West Highland White Terriers
· Standard Poodles
· Bearded Collies
· Portuguese Water Dogs
· Nova Scotia Duck Tolling Retrievers
· Soft Coated Wheaten Terriers
Addison’s disease an affect any breed of dog, as well as mixed breeds, regardless of the age or gender, but it is most common in young, female and middle-aged dogs.
Symptoms of Addison’s disease
Progressive Addison’s disease is hard to diagnose, thanks in part to the wide range of symptoms associated with the disease. It has been called the great imitator. In general, dogs with Addison’s may experience recurrent bouts of gastroenteritis, poor appetite, slow loss of body condition, and an inability to respond appropriately to stress. It's important to note that the symptoms of Addison's disease may wax and wane.
Reduction in aldosterone production has a pronounced impact on the body. It leads to changes in serum levels of sodium, chloride, and potassium, which affects the kidneys. This in turn leads to problems with the heart and circulatory system.
Cortisol, the other major steroid hormone affected by Addison’s, plays a role in almost every important tissue in the dog’s body. It regulates the production of glucose, regulates metabolism, influences the breakdown of fat and proteins, regulates blood pressure, suppresses inflammation, stimulates the formation of red blood cells, and counteracts stress.
Reduction in the production of aldosterone and cortisol causes the symptoms that pet owners and veterinarians most commonly see with the disease.
Symptoms of Addison’s disease:
· Anorexia (lack of appetite)
· Weight loss
· Bloody stools
· Alopecia (hair loss)
· Increased urination
· Increased thirst
· Weak pulse
· Irregular heart rate
· Low temperature
· Painful abdomen
· Hyperpigmentation of the skin
Diagnosing Addison’s Disease in Dogs
Addison’s disease is usually diagnosed during an Addisonian crisis. In an Addisonian crisis, the disease reaches an acute stage, and dogs experience life-threatening symptoms such as shock and collapse.
Once the dog is stabilized from the crisis, we will perform a series of tests to determine what caused the collapse and to rule out other diagnoses. We’ll perform blood work to get a complete blood count and biochemistry and will also most likely run a urinalysis.
Anemia and abnormally high levels of potassium and urea in the blood, along with changes in the levels of sodium, chloride, and calcium in the blood, are symptomatic of Addison’s. The urinalysis may also reveal low concentrations of urine. An electrocardiogram (ECG) may be run to check for changes in your dog’s heart since the elevated potassium is toxic to heart muscle.
The definitive test for Addison’s is the adrenocorticotropic hormone (ACTH) stimulation test. This test monitors the function of the adrenal glands by introducing the synthetic hormone ACTH. We will be measuring the concentration of cortisol before and after ACTH is administered. This lets us know if the adrenal glands are functioning normally.
Treating Addison’s Disease in Dogs
The first thing we need to do is to resolve the crisis your dog may in. He may need to be hospitalized to undergo intensive therapy to manage the symptoms of the crisis. Once your dog is out of immediate danger, we’ll prescribe a replacement hormone medication to help your dog deal with the deficiency. There's usually more than one medication prescribed: a daily steroid (prednisone) and an injectable mineralocorticoid (Percorten or Zycortal) monthly. Also, we will want to run biannual blood work to ensure the medication is working properly.
Addison’s disease is not curable. Your dog will need to take these replacement hormones for the rest of his life, and the dosage may need to be adjusted as time goes by, especially during times of stress.
It takes time to find the right dosage for your dog’s Addison’s disease. Be prepared to visit us frequently for the first couple months after diagnosis, so that we can measure your dog’s hormones and his electrolyte levels. This helps us find the right dosage for your dog. After that, expect to bring your dog in once a month for a shot of replacement hormones, and make sure you follow any additional medication protocols that we may prescribe.
Preventing Addison’s Disease in Dogs
Addison’s disease is not usually preventable. The exception to this is a medication-induced Addisonian crisis. If your dog is on the Cushing's diseasemedications mitotane or trilostane, make sure that you are aware of the symptoms of Addison’s disease in dogs, as an accidental overdose could lead to a crisis. Always keep these medications out of reach of your dog and any children in the house and make sure you monitor your dog’s medications carefully.
Sometimes a rapid withdrawal of a drug like prednisonecan cause Addison’s. Following your veterinarian’s instructions about your dog’s medication is the best way to prevent serious complications like Addison’s disease.