What is Canine Addison’s Disease?Posted: July 21, 2009
In 1849, Thomas Addison wrote about a then-untreatable adrenal gland dysfunction in humans that had no name. A century later, in 1953, the first case of canine Addison’s disease in dogs was recorded. Also known as hypoadrenocorticism, adrenal insufficiency, or hypocortisolism. Addison’s disease isÂ fatal if left untreated.
Addisonâ€™s disease occurs when the adrenal glands, located above the kidneys, fail to produce enough hormones to keep the body functioning normally.
Cortisol production is controlled by the pituitary gland at the base of the brain. The pituitary gland produces adrenocorticotropic hormone (ACTH) which signals the adrenal glands to produce cortisol. A second hormone produced by the adrenal cortex is aldosterone, which together with cortisol assists in regulating dozens of bodily functions, including:
- blood pressure
- cardiovascular function
- immune system inflammatory response
- insulin balance
- metabolism of proteins, carbohydrates, and fats
There are two types of canine Addison’s disease:
Primary Addison’s disease is a problem with the adrenal gland. All dogs with primary Addison’s will develop electrolyte imbalances (although it may show up months or even years after the initial diagnosis). Just because a dog has normal electrolytes doesn’t mean that it doesn’t have Addison’s!
- Typical Addison’s means that the adrenal glands are not working and not producing both cortisol and aldosterone. This could be because of disease, hereditary factors, or many other reasons (See the post on causes of Addison’s Disease in Dogs for full details on causes).
- Atypical Addison’s is where only a part of the adrenal cortex isn’t working; the part that makes cortisol. Dogs with Atypical Addison’s will appear to have normal sodium and potassium levels, making a diagnosis even more difficult. To some veterinarians, typical doesn’t necessarily mean that the dog is deficient in cortisol; it could mean that they don’t have the classic electrolyte changes (low sodium and high potassium) seen in primary Addison’s.
Secondary Addison’s means that the pituitary gland has stopped working properly. Secondary Addison’s disease does not cause electrolyte imbalances, because aldosterone is still being produced by the adrenal cortex.
Your veterinarian will be able to differentiate primary from secondary Addisonâ€™s disease by looking at ACTH or aldosterone levels in the body. With primary Addison’s disease, concentrations of ACTH will be high because the pituitary glands are working normally: with secondary Addison’s disease, levels will be very low. Secondary Addison’s disease is less expensive to treat, but is much rarer than primary Addison’s.
Canine Addison’s disease occurs much more frequently in dogs than in humans; it’s thought to occur one hundred times more often in the canine population. It mainly affects young to middle-age female dogs with the average age at diagnosis being four years old (although it has been found in puppies and dogs up to 12 years old). The majority (about 2/3) are female. Certain breeds are more susceptible:
- Great Danes
- Portuguese water dogs
- standard poodles
- West Highland white terriers
- bearded collies
- Springer spaniels,
- German Shorthaired Pointers
- Soft-Coated Wheaten Terrier
- and Nova Scotia Duck Tolling Retrievers.
Several breeds are particularly not susceptible: American Pit Bull Terrier, American Staffordshire Terrier, Chihuahua, Cocker Spaniel, Golden Retriever, Lhasa Apso, Schnauzer, Yorkshire Terrier.
Whatever breed of dog you own, you should be aware of the symptoms of Addison’s disease; it could strike any dog, at any time. Seek immediate veterinary attention if your dog shows any symptoms of Addison’s disease.
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Novartis Animal Health. Addison’s Disease: Uncommon or Underdiagnosed? Thomson Veterinary Healthcare Communications, Lenexa, Kan, 2003.