Addison’s Disease or Hypoadrenocorticism

Has your West Highland white terrier suddenly collapsed? Does your standard poodle have chronic vomiting and diarrhea? Your pet may be dealing with a condition called Hypoadrenocorticism.

Hypoadrenocorticism, or Addison’s disease, is caused by a lack of corticosteroids and mineralocorticoid secretions from the adrenal glands. In a normally-functioning adrenal gland corticosteroids are released during periods of stress, and mineralocorticoids are released on a regular basis for the maintance of normal electrolyte levels involving sodium (Na), potassium (K), and chloride (Cl-).

Two types of hypoadrenocorticism exist: primary hypoadrenocorticism, which results from a failure of the adrenal glands to secrete glucocorticoids (primarily cortisol) and mineralocorticoids (primarily aldosterone) from the adrenal cortex; secondary hypoadrenocorticism, which is much less common, results from a failure of the pituitary gland to produce ACTH, a hormone that is responsible for stimulating glucocorticoid production from the adrenal glands. With secondary hypoadrenocorticism, mineralocorticoid secretion (aldosterone secretion) is normal.

The most commonly affected breeds of dogs are young to middle-aged (typically 4 to 5 years of age) and include: Great Danes, standard poodles, Portuguese Water Dogs, Nova Scotia duck tolling retrievers, Leonbergers, Rottweilers, Bearded collies, Wheaten terriers, and West Highland white terriers. Each of these breeds has been suggested to have a genetic predilection for hypoadrenocorticism. Several other breeds appear to be predisposed for this disease including Airedale terriers, basset hounds, German shepherds, German shorthaired pointers, Saint Bernards, and Springer spaniels, although as yet a genetic relationship has not been established for these breeds. Seventy percent of affected dogs are female. Castrated male dogs are more commonly affected than are intact male dogs.

Common clinical signs may include sudden acute collapse, weakness, depression, inappetance, vomiting, weight loss, and diarrhea. Additionally, the patient may have bradycardia (slow heart rate), hypothermia (low body temperature), appear to be shaking or shivering, and exhibit abdominal pain. Hematemesis (bloody vomit), melena (blood in the stool), and hematochezia (bloody stool) may occur infrequently. Most dogs will have a waxing and waning of the clinical signs that will typically resolve with fluid and/or corticosteroid administration.

The classical diagnostic laboratory findings involve the electrolyte alteration of hyponatremia (low Na levels) with Hyperkalemia (high K levels). For primary hypoadrenocorticism a decrease in the sodium-potassium ratio from a normal 33:1 to a ratio that is 25:1 or below is typically diagnostic for acute hypoadrenocorticism. Other common laboratory abnormalities include hypoglycemia (low glucose levels), hypochloremia (low blood-chlorine levels), hypocholesterolemia (low cholesterol levels), hypoalbuminemia (low levels of albumin in the blood), and azotemia (high blood-ammonia levels).

On hematology reports these patients may exhibit anemia, eosinophilia (high levels of eosinophils, a certain white blood cell commonly seen in increased levels with allergies and parasitic infections), lymphocytosis (increase in the number of lymphocytes), or a lack of a stress leukogram in an ill patient.

Secondary, or “atypical hypoadrenocorticism”, may not exhibit the characteristic electrolyte alterations seen with primary hypoadrenocorticism.

Most addisonian patients will present with a urine specific gravity of less than 1.030 with concurrent isosthenuria (low levels of urine production), which in the face of azotemia may be incorrectly attributed to primary renal (kidney) failure.

A definitive diagnosis with atypical hypoadrenocortism is based on an ACTH stimulation test. A post-ACTH plasma cortisol concentration of less than 2 µg/dl is consistent with hypoadrenocorticism.   

Treatment consists of prednisone administration at initial doses of 0.5 to 1.0 mg/kg per day. The dose of prednisone should be adjusted up to double the dosage rate the day before an anticipated stressful situation. Patients in acute crises should be placed on IV fluids, preferably NaCL (sodium chloride) and given intravenous corticosteroids.

Mineralocorticoid supplementation with desoxycorticosterone pivalate (DOCP) should be administered as an intramuscular or subcutaneous injection every 25 days. DOCP is available from Novartis Animal Health under the trade name Percorten-V®.    Alternatively, oral fludrocortisone acetate is available from Squibb under the trade name Florinef®, and may be given at a starting dosage of 0.02 mg/kg per day.

Primary adrenal failure is suspected to be immune-mediated (a situation where the body attacks itself) in most cases. Immune-mediated destruction of the adrenal gland may occur concurrently with other immune-mediated endocrine disorders including hypothyroidism, diabetes mellitus, and hypoparathyroidism.

Additional causes of primary adrenal failure include granulomatous destruction or hemorrhagic infarction of the adrenal gland, adrenalitis, neoplasia, amyloidosis, and adrenal necrosis. The use of several drugs may also result in primary hypoadrenocortism: mitotane, trilostane, and ketoconazole. The adrenal suppression caused by ketoconazole and trilostane may be reversible, but adrenal failure resulting from mitotane is permanent.

Secondary hypoadrenocorticism may result from destructive lesions in the hypothalamus or pituitary gland secondary to neoplasia, inflammations, or trauma. An idiopathic (reason unknown) ACTH deficiency may also occur. Chronic administration of glucocorticoids may also cause secondary adrenal failure through the suppression of ACTH production.

Life-long treatment is necessary. With adequate treatment a dog may lead a long and happy life.

References:

Bonagura, John and David Twedt, Ed. Kirk’s Current Veterinary Therapy XIV. W.B. Saunders. 2009. Pp. 231-235.

Ettinger, Stephen and Edward Feldman Ed. Veterinary Internal Medicine. 5th Edition. Vol. 2. W.B. Saunders. 2000. Pp. 1488-1499.

Hoskins, Johnny. “Testing for Addison’s Disease.” DVM Newsmagazine. January 2009. Pp. 8S-12S.

Kirk, Robert and Stephen Bistner. Handbook of Veterinary Procedures and Emergency Treatment. W.B. Saunders and Co. 1981. P. 116-117.

Lathan, Patty and Catharine Scott-Moncrieff. “Hypoadrenocorticism in Dogs. NAVC Clinician’s Brief. February,. 2007. Pp. 21-22.

Topics: great danes, poodles, portuguese water dogs, west highland white terriers

Symptoms: collapse, diarrhea, vomiting

Similar entries

  • Is your ferret losing hair and has skin that appears to be normal? Your pet may be suffering from ferret adrenal gland disease.

  • Recently chosen to be the First Dog of the United States, the once-obscure Portuguese Water Dog has gained new notoriety. President Obama and his family have chosen a Portuguese Water Dog to become the newest resident of 1600 Pennsylvania Ave in Washington, D.C.

  • Obesity is defined as an increase in body weight beyond optimal skeletal and physical requirement, as the result of an excessive accumulation of fat in the body. Obesity may be due to metabolic or internal (endocrine) abnormalities known as endogenous causes or exogenous obesity due to overeating. Exogenous obesity is the end result from an imbalance between calorie intake and the expenditure of energy used in day to day activities.

  • Has your dog been losing weight lately, exhibiting chronic vomiting, had diarrhea, or hematochezia (blood in the feces)? Alternatively, does your dog have an ulcerated, draining skin lesion that just won’t heal? Is your dog a sports breed like a Labrador retriever, or does he love the water? Do you live in an area with a warmer climate? Then your dog could be suffering from an infection called Pythiosis.

  • Is your dog having trouble getting around? Do you think your dog may be running an elevated temperature? Think you might help him out by giving him an aspirin? Don’t! Aspirin may be toxic to your pet, especially in high doses.