hypoadrenocorticism

Question 1

Classic findings of Addison’s disease:

Answer 1

• Absent stress leukogram
• Hyperkalemia
• Hyponatremia
• Na+/K+ ratio < 27
• Azotemia
• Mild to moderate metabolic acidosis
• +/- hypercalcemia (30% of cases)

Question 2

what is addisons disease? common? signalment?

Answer 2

HYPOADRENOCORTICISM
* Dysfunction of the adrenal cortex
* Uncommon endocrinopathy
* Most prevalent in:
> Young to middle aged
> Female dogs

Question 3

Addison’s disease means deficient secretion in:

Answer 3

Mineralocorticoids
* Aldosterone
> Na+, K+ & water regulation
<><><>
Glucocorticoids
* Cortisol
> Stress response

Question 4

adrenal cortex zones, and what they do?

Answer 4

1. Zona glomerulosa:
   * Synthesizes & secretes mineralocorticoids
   > Aldosterone
   <><>
2. Zona fasciculata:
   * Synthesizes & secretes the glucocorticoids
   > Cortisone & cortisol
   <><>
3. Zona reticularis:
   * Synthesizes & secretes sex hormones
   > Androgens & estrogens
   * Secretes the same glucocorticoids as the zona fasciculata

Question 5

categories of hypoadrenocorticism - primary vs secondary

Answer 5

Primary hypoadrenocorticism
* Adrenal atrophy or destruction
<><>
Secondary hypoadrenocorticism
* Deficiency in pituitary ACTH production
* Lack of stimulation of the adrenal glands

Question 6

types of primary hypoadrenocorticism

Answer 6

• typical
• atypical
• iatrogenic

Question 7

types of secondary hypoadrenocorticism

Answer 7

• uncommon
• iatrogenic

Question 8

primary hypoadrenocorticism - how common? what happens?

Answer 8

• Typical, most common presentation
• Bilateral atrophy or destruction of all 3 layers of the
  adrenal cortices
  > Glucocorticoid & mineralocorticoid secretion affected

Question 9

primary hypoadrenocorticism causes

Answer 9

• Immune-mediated destruction
• Infiltrative disease
  > Fungal infections, neoplasia
  > Amyloidosis
  > Hemorrhagic disorders / coagulopathies
  <><>
• Iatrogenic
  > secondary to mitotane / trilostane therapy

Question 10

atypical addisons - what is it? difference from classic / typical?

Answer 10

• Atypical Addison’s disease
  > Subgroup of 1° hypoadrenocorticism
  <><><>
• Bilateral destruction of zona fasciculata & zona reticularis only
  > Glucocorticoids affected; Mineralocorticoids spared
  > Electrolyte disturbances not appreciated
• Gradually progressive disorder

Question 11

what is secondary hypoadrenocorticism? how does it often come about? what is affected?

Answer 11

Deficiency in ACTH production from the pituitary
* Other pituitary dependent hormones frequently
also affected
* Rare ie. head trauma
<><><>
At the level of the adrenals
* Glucocorticoid production affected
* Mineralocorticoid production usually preserved
> No electrolyte abnormalities

Question 12

Drug induced hypoadrenocorticism - causes

Answer 12

Administration of drugs that:
* Directly inhibit glucocorticoid production
> Secondary
OR
* Adrenocorticol lysis
> Primary

Question 13

Primary iatrogenic hypoadrenocorticism - how it arises? what is affected?

Answer 13

• Mitotane / trilostane therapy for Cushing’s disease
• Administration of drugs that produce adrenocorticol lysis
• Both Glucocorticoid & Mineralocorticoid deficiency

Question 14

Secondary iatrogenic hypoadrenocorticism - how it arises? what do we see?

Answer 14

• Administration of drugs that directly inhibit glucocorticoid production
• Ie. Corticosteroid administration
  <><><>
• Corticosteroids, via a negative feedback system, depress ACTH production
• Lack of ACTH causes bilateral adrenal atrophy
• On rapid discontinuation of corticosteroids, adrenals unable to respond adequately
  > Glucocorticoid deficiency only
  > Electrolyte disturbances not appreciated

Question 15

hypothalamic pituitary adrenal axis - how it works?
- relationship to prednisone, exogenous corticosteroids?

Answer 15

stressors cause hypothalamus to release CRH
> CRH causes release of ACTH from anterior pituitary
> ACTH causes release of cortisol from adrenal gland
> metabolic effects…..
> cortisol acts on AP and hypothalamus to stop them from secreting ACTH and CRH respectively (negative feedback)
<><><><>
- PREDNISONE = Exogenous ’cortisol’
- always wean corticosteroids!
- On rapid discontinuation of corticosteroids, adrenals unable to respond adequately

Question 16

Addison’s Predisposed breeds:

Answer 16

Great Dane
Poodle (all sizes)
West Highland White Terrier

Question 17

Familial predispositions to addison’s in what breeds?

Answer 17

• Portuguese Water Dog
• Leonberger
• Nova Scotia Duck Tolling Retriever
• Bearded Collie

Question 18

Acute Addisonian Crisis
- significance?
- clinical findings?

Answer 18

Life threatening emergency
<><><>
Clinical findings:
* Shock / Hypovolemia
* Collapse
* Bradycardia
* Hypotension
* Hypothermia
* Pale or injected mucous membranes
* GI hemorrhage
> Hematochezia / Melena

Question 19

types of signs we can see from addison’s, in broad categories

Answer 19

1. Acute Collapse Shock
2. Waxing & Waning Non-Specific Signs

Question 20

signs we would see in an acute case of addisons

Answer 20

Acute Collapse Shock
* Hypothermia
* Slow CRT
* Injected vs pale mucous membranes
* Weak Pulse / Hypotension
* Bradycardia
* GI hemorrhage
* Painful Abdomen

Question 21

waxing and waning, non-specific signs we might see from addison’s

Answer 21

• Lethargy / depression
• Anorexia / weight loss
• Vomiting
• Diarrhea
• Weakness
• PU/PD
• Hair loss
• Previous response to therapy

Question 22

how do we diagnose addisons?

Answer 22

Given that the historical & clinical findings are vague, non-specific, often intermittent & found with many other disease processes
* High Index of Suspicion

Question 22

why is addison’s known as ‘the great pretender’? what can Addison’s look like?

Answer 22

• No pathognomonic signs
  > Waxing & Waning illness
• Signs are common to a wide variety of more
  prevalent diseases
• Duration
  > Chronic progressive signs (up to 1 year)
• May culminate in fulminant acute adrenal crisis

Question 23

clinical abnormalities seen in addisons?
- electrolytes
- CBC
- urinalysis

Answer 23

• increased K+
• decreased Na+
• Na+/K+ ratio <27
• decreased Cl-
• increased Ca2+
• increased Phos
• Azotemia
• Hypoglycemia
  <><>
  CBC:
• Anemia
• Eosinophilia
• Lymphocytosis
• Lack of stress leukogram
  <><>
  Urinalysis
• USG < 1.030