Dog News

Addison’s Disease

by Shawn Finch, DVM

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Addison’s disease is the common name for hypoadrenocortisism.  The most simple (and sort of accurate) definition of Addison’s disease is “the opposite of Cushing’s disease.” Cushing’s disease (hyperadrenocortisism) is characterized by an excess of cortisol, and Addison’s disease is characterized by a deficiency of cortisol and aldosterone.

Last week we discussed what happens when adrenal glands, for a myriad of different reasons, become overactive.  What happens when the adrenal glands are underactive?  And why would they slack off when they are known for being so hard-working?  Would cortisol and aldosterone be missed if they were no longer being produced by the adrenal glands? Would you ever ask these questions if I were not making you wonder?  I am sure you have if you have a dog with Addison’s disease!

Big Stupid Medical Words

(Note:  I LOVE big stupid medical words.  I am hoping that if you do not yet, you will soon.  No other languages lend themselves better to highly specific and obnoxiously compounded words than Greek and Latin.  Awesome.)

Adrenal glands – These are two little triangle shaped organs, one near each kidney.  The adrenal glands produce stress hormones, help balance electrolyes, oversee the production of sex hormones and manage the body’s “fight or flight” response.

ACTH – adrenocorticotropic hormone – This is a hormone produced and secreted by the pituitary gland that signals the adrenal glands to produce cortisol.

Cortisol – This is the body’s main steroid hormone.  It is produced and secreted by the cortex (outer layer) or the adrenal gland.  It supports life and helps manage the body’s stresses.

Aldosterone – This is another steroid hormone (more specifically a mineralocorticoid, mineral = salt,  See?  Aren’t medical words awesome??)  It is also produced and secreted by the cortex of the adrenal gland.  It signals the kidneys to retain appropriate amounts of sodium and chloride and water and release excess potassium as waste.

Electrolytes – “salts,” or, more specifically, ions that are electrically charged (positive or negative) in solution.

Today’s Electrolytes of Interest – sodium (Na+), chloride (Cl-) and potassium (K+).

Which Dogs?

Addison’s disease is uncommon in dogs and rare in cats.  Addison’s disease seems a bit more “random” in which dogs are affected than Cushing’s disease.  It affects dogs of all ages.  It affects all breeds and mixes, but has been reported more often in Great Danes, Rottweilers, Portuguese Water Dogs, Standard Poodles, West Highland White Terriers and Wheatens (1), and also Bearded Collies and Leonbergers, though the more rare a disease (and a breed!) is, the more difficult it can be to determine patterns.

(1)  Kinzter PP. Hypoadrenocorticism. In: Tilly LP, Smith FW, eds. The 5 Minute Veterinary Consult. Ames: Blackwell, 2007:656.

Peanut is an eighteen (18!) year old mixed breed dog belonging to my friend Tammy Hall.  Peanut was diagnosed with Addison’s disease ten years ago, and is doing wonderfully on medication and periodic wellness exams and blood work.  She is otherwise healthy.  (As Dave Barry so often says, “I am not making this up!”)  Every time I see Peanut, I am encouraged.


Living well with Addison’s disease is possible.

Causes of Addison’s Disease

Most cases of Addison’s disease are thought to be caused by dysfunctions of the immune system that destroy part of the adrenal cortices, causing insufficient cortisol and aldosterone production.

Less commonly, something malfunctions in the pituitary gland causing decreased ACTH production and thus decreased cortisol production by the adrenal glands (secondary Addison’s disease).  Other causes, such as certain cancers, are rare.

A dog can develop iatrogenic Addison’s disease (iatrogenic – “i” caused it!) if long term steroid use is abruptly discontinued or if medication for Cushing’s disease is given at a high enough dose to destroy more of the adrenal glands than what was intended.

A Lack of Cortisol

Cortisol is needed for many of the body’s day to day functions and to manage both normal and excessive stress.  A lack of cortisol may be characterized by vomiting and diarrhea and decreased appetite.

A Lack of Aldosterone – You Never Appreciate Electrolytes Until They Are Unbalanced

Aldosterone signals the kidneys to retain appropriate amounts of sodium and chloride and water and release excess potassium as waste.  Without it, too much salt (sodium and chloride) will be lost, too much water will be lost and too much potassium will be retained.  All of these need to be intricately balanced on a cellular level.  When they are not, bad things happen to every body system, though some are hit harder than others.

High potassium can cause heart rhythm disturbances.  Loss of salt can cause vomiting and diarrhea.  Dehydration causes lethargy.  Dehydration, salt loss and excess potassium together will cause low blood pressure, weakness and PU/PD (polyuria – excess urination, polydipsia – excess thirst) as the dog’s body tries to bring everything back into balance.

Diagnosing Addison’s Disease

It used to be that nonspecific ailments in the veterinary world were often treated with steroids and supportive care.  As frustrating as that can be for veterinarians today (I would never yell at my hero James Herriot, but sometimes I have yelled at his cure-all treatments while reading his books…) many a life has been saved by this “fix all” including many pre-diagnosis Addison’s disease sufferers.

Today, we try to diagnose the specific cause of clinical signs as often as possible, and have better tools with which to accomplish that than in days past.  So, often we will suspect Addison’s disease if a pet is showing signs, non-specific as they are, and do bloodwork.

If liver and kidney values are elevated, and especially if electrolytes are unbalanced – high potassium and low sodium and low chloride – we really become suspicious.

A diagnosis is made by checking cortisol levels before and after giving ACTH by injection.  If cortisol starts and remains low despite the ACTH injection, we have a diagnosis of Addison’s disease.

Even though we can “pin down” Addison’s disease much more effectively than we used to be able to, it still can be a nebulous diagnosis, refusing to read the text books and refusing to present with classic signs and lab work.  With atypical and secondary Addison’s disease, electrolytes (one of the big markers we look for) may not even be out of whack.

Treating Addison’s Disease

An “Addisonian crisis” – an event in which a pet with Addison’s disease becomes critically ill –  is treated with intensive care, steroids and intravenous fluids plus specific treatment as needed for clinical signs, such as low blood pressure, vomiting and diarrhea.  An Addisonian crisis often precedes the diagnosis of Addison’s disease.

Addison’s disease is treatable, but if unchecked can be fatal.  Once the patient is stabilized, diagnosed and on the correct dose of medication, crises are much less common, though they can still happen.  Medication doses may need to be adjusted periodically for a dog with Addison’s disease, more often at the beginning of the course of the disease than later.

Stable Addison’s disease is treated by artificially replacing the aldosterone and cortisol the body’s adrenal glands are not making. This is done with oral fludrocortisone acetate (Florinef) or injectable desoxycorticosterone pivalate (DOCP, Percorten-V) and, if needed, “physiologic” doses (low doses to match what the body should be producing) of prednisone.

Higher doses of prednisone are given to an addisonian pet when he or she is expected to be under more stress than normal, such as when boarding or undergoing anesthesia or when ill.  Pet parents also become skilled at knowing when pets are already stressed and may need “boosts” of prednisone.  Two of the biggest “tells” are decreased appetite and lethargy.  Wellness examinations and blood work are repeated routinely once the pet is stable.  Addison’s disease, though a high maintenance and lifelong condition, generally has a good prognosis.

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Have you had or known a dog or other pet with Addison’s disease?  What have been your experiences with diagnosis, treatment, and prognosis?  Have your pets with Addison’s disease done well?  I sure hope so.

I will repeat what I said last week when we talked about Cushing’s disease, because though they are on opposite ends of the adrenal disease spectrum, I believe the “blessing” is appropriate for Addison’s disease as well…

I hope that your only experience with this complex and intriguing disease is  this post, and that all of your pets (even, and perhaps especially, your Addisonian friends) have a long and healthy life filled with intricately and perfectly balanced levels of stress hormones and electrolytes!


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