Addison's Disease

The following article was composed by Rachel Peeples, DVM

The adrenal gland in the canine body is responsible for making several hormones, two of which are glucocorticoids and mineralocorticoids.

Glucocorticoids (better known as hydrocortisone, prednisone, etc) act as antiinflammatories and as catabolic agents, that is they promote the break down of protein, fat, etc for energy.  They also have a variety of less well described functions.  Mineralocorticioids are responsible for maintaining proper level of Potassium and Sodium primarily but other electrolytes as well.  Addison's Disease is also known as adrenal insufficiency or hypoadrenalcorticism and is characterized by a lack or insufficient production of both glucocorticoids and mineralocorticoids.

Thus, the signs seen are related to the lack of these two hormones in particular mineralocorticoids.  In Addison's disease, the potassium levels become elevated with subsequent nausea, vomiting, lethargy, and slow heart rate.  The heart rate can become so slow as to compromise life.  This is the primary way that Addisonian dogs present -- either as intermittent vomiting, diarrhea, depression that is corrected with fluid therapy (ie correcting the electrolyte imbalance) or in life-threatening shock from compromised cardiovascular output.  Treatment is to correct the immediate threat -- ie the electrolyte imbalance and then to address the underlying problem of lack of these two hormones.  Hydrocortisone is the natural glucocorticoid, and, thus, is used.   Maintenance doses are given daily with higher stress doses given as needed.  Mineralocorticoids are provided in a number of ways the most popular currently being a depot injection that lasts around 4 weeks.

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