Hypoadrenocorticism, also referred to as Addison’s Disease, is a disease that occurs when there is damage to the adrenal glands. The most common cause is an autoimmune condition in which the body’s immune system attacks healthy cells (in this case cells in the adrenal glands). Other less common causes include cancers (such as lymphoma with spread to the adrenal glands or tumors in the pituitary gland that produces a hormone called Adrenocorticotropic Hormone or ACTH that stimulates the adrenal glands to produce their hormones), severe infections such as septicemia or certain fungal infections, or a condition called iatrogenic hypoadrenocorticism (caused by a rapid discontinuation of corticosteroid treatments temporarily causing the adrenal glands to stop producing corticosteroids – the term iatrogenic referring to something we caused with treatment). Auto immune causes have been confirmed to occur in Portuguese Water Dogs, show a high incidence in with suspected genetic cause in some other breeds (Standard Poodles, Bearded Collies, Nova and Scotia Duck Tolling Retriever, Great Danes, Rottweilers, Leonbergers and West Highland White Terriers) and moderately higher incidence with genetic cause suspected in other breeds (Labrador and Golden Retrievers, Saint Bernards, Cocker Spaniels and Pomeranians). A higher occurrence in female dogs has been shown. Hypoadrenocorticism can occur in any other dog breeds and again autoimmune disease is suspected to be the most common causes (biopsy samples of the adrenal gland after death has shown a lymphoplasmacytic infiltration at the adrenal cortex – an inflammatory response seen with autoimmune disease).
The adrenal gland actually has 3 layers including the outer layer – the adrenal cortex (produces mineralocorticoids or aldosterone), the middle layer or medullary region (produces cortisol, epinephrine and norepinephrine) and an inner layer (produces androgens or sex hormones such as estrogen, progesterone and testosterone). These small little glands (smaller than a peanut) are essential in maintaining homeostasis (maintaining a normal physiological state) through action on many systems in the body. The aldosterone produced in the renal cortex regulates the balance of sodium and potassium ions (regulated in the kidneys) and water balance as well as acid-base balance. The glucocorticoids, epinephrine and norepinephrine produced in the medullary region maintain balance of glucose, fatty acids and proteins needed for energy or cellular metabolism, as well as maintaining blood pressure and increasing heart rate and decreasing the inflammatory response with infection or injury. The sex hormones produced in the inner layer is less focused on in the treatment of hypoadrenocorticism due to its less generalized effect however does contribute to dermatologic signs seen such as changes in the coat, hyperpigmentation of the skin as well as some other effects (these hormones are still produced after spay or neuter in dogs). An acronym called SSS has been used to simplify the function of these different layers (Salt, Sugar and Sex).
All of these hormones act together to maintain homeostasis and account for the wide range of signs or symptoms seen with this disease. Addisons Disease has been called “the great pretended” because of how many things it can look like. Early signs or symptoms include lethargy, vomiting, diarrhea, decreased appetite, weakness, excessive drinking and urinating, changes in the coat, dandruff, skin infections and other dermatologic conditions. In more severe presentation or what is called and Addisonian Crisis, signs seen include severe dehydration, hypotension and low heart rate (all contributing to shock), severe electrolyte changes, hypoglycemia (low blood glucose), potential seizures and collapse. The lack of production of cortisol, epinephrine and norepinephrine interrupts the body’s normal “fight-or-flight” response (changes made by the sympathetic nervous system). Dogs presenting in an Addisonian Crisis are critical and need to be admitted to hospital for treatment. The conditions are sometimes mistaken for other conditions such as acute kidney failure or insulin producing tumors in the pancreas. Screening for hypoadrenocorticism is simple and always recommended first when suspected and presenting in a critical state. An ACTH stimulation test (a test in which a cortisol level is first checked and a synthetic version of Adrenocorticotropic Hormone is administered to check response).
This all sounds very frightening and although it should sound frightening, with appropriate monitoring and initial treatments, most dogs recover and are able to be discharged from hospital. Although the condition cannot be cured, lifelong treatments can be simple and with proper education, consistent care, and follow up with a veterinarian, most dogs will go on to live a full life and recover to normal activity. Ongoing treatments require treatment with both mineralocorticoids and glucocorticoids. Supplementation with an injectable form called Desoxycorticosterone or DOCP (trade names Zycortal and Percorten-V) or an oral form mixed with a glucocorticoid (Fludrocortisone Acetate or Florinef). Most veterinarians find treatment with the injectable DOCP administered every 3-4 weeks with adjustment of the frequent based on monitoring and response to treatment and an oral glucocorticoid (typically Prednisone or Prednisolone) administered at a physiologic dose. Follow ups with recheck of electrolytes, cortisol levels and sometimes other screening tests are recommended on a regular basis and consistency of treatments is essential. Some dogs present with only glucocorticoid dependent states and do not initially need treatment with mineralocorticoids (this has been termed atypical Addisons disease). These are typically dogs with an earlier diagnosis. Many or most of these cases will still progress to mineralocorticoid deficiency. They should be monitored closely with recheck laboratory monitoring for elevation of kidney values or electrolyte abnormalities (recheck every 2-3 months would be recommended). Although these cases can be managed, it would be best to keep them out of the ER or ICU. Dogs with well managed mineralocorticoid and glucocorticoid dependent Addisons disease may still need higher dosing of prednisone or prednisolone with stress (either normal day to day stress or physiologic stress associated with other disease states). If you are ever concerned, you should have them evaluated by a veterinarian.
Seeing dogs recover well and go on to live a healthy lifestyle is one of the most rewarding emergencies to see. We love to see things we can fix or at least treat with a good outcome. So, great pretender, you are not fooling us and we would be happy to knock you down again.
