Canine hypoadrenocorticism (Proceedings)


Canine hypoadrenocorticism (Proceedings)

Aug 01, 2008

Canine Hypoadrenocorticism

1. Introduction

A. Etiology

1. Primary adrenocortical failure (Addison's disease)

A. Auto-immune disorder (Most common type)

B. Destructive lesions

1. Histoplasmosis

2. Blastomycosis

3. Metastatic neoplasia

C. Infarction of adrenals

D. Amyloidosis

E. Secondary to o,p'-DDD

2. Secondary (lack of ACTH secretion)

A. Destructive lesions of pituitary/hypothalamus.

B. Chronic, excessive steroid use.

C. Hypopituitarism

D. Idiopathic

2. Signalment

A. Young to middle age.

B. Females > Males (80% Female).

C. May be a breed predilection in Standard Poodles.

3. Pathophysiology

A. Requires 90% loss of adrenal cortex.

B. Destruction is usually gradual and symptoms first appear during times of stress (trauma, surgery, infection). Ultimately, hormone secretion is inadequate even under normal conditions.

C. Lack of glucocorticoids

1. Gastrointestinal effects

A. Anorexia

B. Vomiting

C. Abdominal Pain

D. Weight loss

2. Mental changes

A. Lethargy

3. Metabolic effects

A. Decreased gluconeogenesis.

B. Decreased fat metabolism and utilization.

C. Hepatic glycogen depletion leading to fasting hypoglycemia.

D. Lack of aldosterone

1. Inability to conserve sodium

A. Hypovolemia

B. Weight loss

C. Decreased blood pressure

D. Decreased cardiac output

E. Decreased renal blood flow; pre- renal azotemia

F. Weakness

2. Inability to excrete potassium

A. Due to reduced GFR

B. Decreased excitability of heart

C. Slows conduction (EKG abnormalities)

E. o,p'-DDD therapy can produce similar signs

1. Sodium and potassium should be monitored during therapy.

F. Secondary adrenal insufficiency

1. Aldosterone normal so no electrolyte abnormalities.

2. Signs due to glucocorticoid insufficiency.

4. Clinical Signs

A. Waxing - waning course

B. Lethargy/depression

C. Weakness

D. Anorexia/weight loss

E. Vomiting/diarrhea/melena

F. Abdominal pain