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Addison’s Disease

Hypoadrenocorticism or Addison’s Disease
(Inadequate Production of Hormones by the Adrenal Glands)

OVERVIEW

  • A hormonal disorder resulting from decreased production of hormones (glucocorticoids and/or mineralocorticoids) by the adrenal glands
  • “Glucocorticoids” are a class of hormones produced by the adrenal glands; they typically are called “steroids”; glucocorticoids are involved in metabolism and the stress response and they have anti-inflammatory properties
  • “Mineralocorticoids” are another class of hormones produced by the adrenal glands; they are involved in regulation of salt (sodium and potassium) in the body; “aldosterone” is a mineralocorticoid that regulates sodium and potassium in the body
  • Addison’s disease refers to decreased production of both glucocorticoids and mineralocorticoids
  • Glucocorticoid (cortisol) deficiency contributes to lack of appetite (known as “anorexia”); vomiting; black, tarry stools (due to the presence of digested blood; condition known as “melena”); sluggishness (lethargy); and weight loss
  • Inadequate glucocorticoid levels increase likelihood of the pet developing low blood glucose or sugar (known as “hypoglycemia”)
  • Mineralocorticoid (aldosterone) deficiency results in an inability to retain sodium in the body and to excrete potassium from the body; decreased sodium levels lead to diminished circulating blood volume that in turn contributes to low blood pressure (known as “hypotension”), dehydration, weakness, and depression; increased levels of potassium in the blood (known as “hyperkalemia”) may result in heart-muscle toxicity

Genetics

  • A genetic basis has been determined in standard poodles, bearded collies, and Leonbergers

Signalment/Description of Pet

Species

  • Dogs
  • Cats

Breed Predilections

  • Great Danes, rottweilers, Portuguese water dogs, standard poodles, bearded collies, Leonbergers, West Highland white terriers, and soft-coated wheaten terriers have increased risk as compared to other dog breeds
  • No breed predilection in cats

Mean Age and Range

  • Dogs—range, less than 1 year to greater than 12 years of age; median, 4 years of age
  • Cats—range, 1–9 years of age; most are middle-aged

Predominant Sex

  • Female dogs are more likely to have hypoadrenocorticism than male dogs
  • No predominant sex in cats

Signs/Observed Changes in the Pet

  • Signs vary from mild and few in some pets with long-term (chronic) low levels of steroids produced by the adrenal glands (hypoadrenocorticism) to severe and life-threatening disease in a sudden (acute) Addisonian crisis (condition in which the pet is in shock and collapse, usually with low body temperature [known as “hypothermia”], weak pulse, and an unexpectedly slow heart rate)
  • Dogs—sluggishness (lethargy); lack of appetite (anorexia); vomiting; weight loss; signs vary in intensity—they may increase and decrease over time (known as a “waxing and waning” course); diarrhea; shaking; increased urination (known as “polyuria”) and increased thirst (known as “polydipsia”)
  • Dogs—depression; weakness; dehydration; collapse; low body temperature (known as “hypothermia”); black, tarry stools (melena); weak pulse; slow heart rate (known as “bradycardia”); painful abdomen; hair loss
  • Cats—sluggishness (lethargy); lack of appetite (anorexia); vomiting; increased urination (polyuria) and increased thirst (polydipsia); weight loss
  • Cats—dehydration; weakness; weak pulse; slow heart rate (bradycardia)

Causes

  • Primary hypoadrenocorticism—unknown cause (so-called “idiopathic disease”); immune-mediated disease; side effect of medication (mitotane or trilostane) used to treat excessive production of steroids by the adrenal glands (condition known as “hyperadrenocorticism” or “Cushing’s syndrome”); cancer; fungal disease; blood clotting disorder (known as “coagulopathy”)
  • Secondary hypoadrenocorticism—side effect of medical treatment with steroids, when long-term steroid administration is discontinued; abnormalities in the pituitary gland; the “pituitary gland” is the master gland of the body—it is located at the base of the brain; it controls many other glands in the body

Risk Factors

  • Treatment for excessive production of steroids by the adrenal glands (hyperadrenocorticism or Cushing’s disease)
  • Long-term use of steroids in medical treatment

Treatment

Health Care

  • A sudden (acute) Addisonian crisis (condition in which the pet is in shock and collapse, usually with low body temperature [hypothermia], weak pulse, and an unexpectedly slow heart rate) is a medical emergency requiring intensive therapy
  • Treat sudden (acute) Addisonian crisis with rapid correction of low blood volume (known as “hypovolemia”) using isotonic fluids (preferably 0.9% NaCl)
  • Monitor blood pressure, urine output, and heart rate and rhythm
  • Treatment of long-term (chronic) hypoadrenocorticism depends on severity of clinical signs; usually initial stabilization and therapy are conducted on an inpatient basis

Activity

  • Avoid unnecessary stress and exertion during an Addisonian crisis

 Diet

  • No alteration necessary

Follow-Up Care

Patient Monitoring

  • After the first two injections of DOCP, ideally do bloodwork and measure serum electrolyte (especially sodium and potassium) levels at 2, 3, and 4 weeks to determine duration of effect; thereafter, check electrolyte levels at the time of injection for the next 3–6 months (and adjust the dosage of DOCP, if necessary) and then every 6 months
  • Adjust the daily dose of fludrocortisone, based on serial bloodwork (serum electrolyte determinations); following initiation of therapy, check serum electrolyte levels weekly until they stabilize in the normal range; thereafter, check serum electrolyte concentrations and blood urea nitrogen or creatinine monthly for the first 3–6 months and then every 3–12 months

Preventions and Avoidance

  • Continue adrenal hormone replacement therapy for the lifetime of the pet
  • Increase the dosage of replacement glucocorticoids or steroids during periods of stress (such as travel, hospitalization, and surgery), as directed by your pet’s veterinarian

Possible Complications

  • Increased urination (polyuria) and increased thirst (polydipsia) may occur from prednisone administration, necessitating decreasing or discontinuing the drug
  • Increased urination (polyuria) and increased thirst (polydipsia) may occur from fludrocortisone administration, necessitating a change to DOCP therapy

Expected Course and Prognosis

  • Most affected pets carry a good to excellent prognosis following proper stabilization and treatment
  • Pets with underlying tumors or cancer have less favorable prognoses

Key Points

  • Lifelong glucocorticoid and/or mineralocorticoid replacement therapy is required
  • Increased dosages of glucocorticoids or steroids are required during periods of stress (such as travel, hospitalization, and surgery), as directed by your pet’s veterinarian

 

Blackwell’s Five-Minute Veterinary Consult: Canine and Feline, Fifth Edit