Hypoadrenocorticism

Question 1

What is the other name use for hypoadrenocorticism?

Answer 1

Addisons disease

Question 2

What is the cause of hypoadrenocorticism?

Answer 2

Lack of mineralocorticoid and/or glucocorticoid secretion by the adrenal cortex

Question 3

Describe primary hypoadrenocorticism

Answer 3

Caused by destruction of more than 95% of the adrenal cortex leading to a deficiency of mineralocorticoid and glucocorticoid secretion.
It is termed Addisons disease

Question 4

Describe secondary hypoadrenocorticism

Answer 4

Deficiency in ACTH secretion by the pituitary gland leading to atrophy of the adrenal cortices and decreased/absent glucocorticoid secretion. Mineralocorticoid secretion remains sufficient.

Question 5

Describe the predispositions for hypoadrenocorticism

Answer 5

• Uncommon - best not to miss
• Middle aged female
• Standard Poodle, Beardies, Gt Dane, Portugese Water Dog, WHWT, St B, Wheaten T, Rottie Leonberger
• Nova Scotia Duck-Tolling Retriever 10x more common, affects siblings

Question 6

List the clinical signs of acute hypoadrenocorticism

Answer 6

• Severe depression/collapse
• Hypovolaemic
• Weak pulses
• Pale mm
• Bradycardic
• Dehydration
• Hypothermic

Question 7

List the clinical signs of chronic hypoadrenocorticism

Answer 7

• Intermittent malaise
• Vomiting
• Diarrhoea
• Lethargy
• Weight loss
• Intermittent collapse
• Vague and intermittent

Question 8

What is the cause of bradycardia in hypoadrenocorticism?

Answer 8

High potassium levels.
- Dehydration would normally cause tachycardia so the bradycardia suggests potassium levels have increased

Question 9

Describe the haematology changes seen in hypoadrenocorticism

Answer 9

• Mild non- regenerative anaemia: due to chronic disease or recent haemorrhage
• Mild hypercalcaemia: due to shift in electrolyte balances and reduced excretion by the kidneys
• Pre-renal azotaemia: chronic dehydration -> decreased GFR -> raised urea and creatinine
• Lymphocytosis +/- eosinophilia = Inverse stress leukogram due to lack of glucocorticoids

Question 10

Describe the sodium and potassium changes seen in hypoadrenocorticism

Answer 10

Animals with Addisons are deficient in mineralocorticoids (aldosterone) and therefore have
increased loss of sodium and chloride in the urine and reduced excretion of potassium

Question 11

Describe the main features of atypical Addisons

Answer 11

Cortisol deficiency
Normal Mineralocorticoids
Usually progress to mineralocorticoid deficiency
May have abnormal aldosterone stimulation

Question 12

List the DDx for high potassium and low sodium levels

Answer 12

Gastrointestinal disease
Renal failure (acute or chronic)
Parasitic infection (whipworms)
Urinary obstruction
Chronic effusion with repeated drainage
Pregnancy
Congestive heart failure
Diabetes mellitus
Chronic blood loss

Question 13

Describe the changes seen on the ECG of patients with Addisons

Answer 13

Bradycardia
Tall, narrow T waves
Prolonged QRS interval
Decreased P wave amplitude
Prolonged P-R interval
Absent P wave
Complete heart block
Ventricular arrhythmias

Question 14

How can Addisons be detected on radiography?

Answer 14

Hypovolaemia signs: microcardia, reduced vascular pattern and a small vena cava

Question 15

Which test can be used to rule out Addisons

Answer 15

Basal cortisol using a single ACTH stimulation test

Question 16

Describe the results of the ACTH stimulation test in Addisons

Answer 16

Dogs with Addisons have a low resting cortisol level and have a subnormal or negligible response to ACTH (few dogs with a basal cortisol > 50nmol/l turn out to have Addison’s).
The same result will be obtained in an animal that has been on steroids, so make sure that you rule this out before making a diagnosis.

Question 17

Describe fluid therapy for dogs with Addisons

Answer 17

• IV fluids at 3-4 times maintenace.
  Use fluids that are low in potassium and preferably 0.9% NaCl.
• Glucose can be added to the drip if necessary to make a 5% solution, as this will cause insulin release and reduce hyperkalaemia

Question 18

Describe steroid treatment for acute Addisons patients

Answer 18

An ACTH stimulation test should be performed before starting glucocorticoid therapy.
If the animal is extremely sick and treatment has to be initiated straight away, dexamethasone is the glucocorticoid that least interferes with the test.
As soon as the ACTH stimulation test has been performed, the animal should be treated with dexamethasone

Question 19

Describe steroid therapy for stabilised Addisons patients

Answer 19

Oral prednisolone
Fludrocortisone

Question 20

What are the side effects of Addisons treatment?

Answer 20

Acute renal disease
Myelinosis
- Depression, weakness, ataxia, tetraparesis, and decreased sensory perception
- Signs occur days later and are often irreversible

Question 21

Describe the prognosis of Addisons

Answer 21

Lifelong therapy
Add glucocorticoid when stressed
Normal life expectancy when treated and monitored correctly

Question 22

What is the cause of hyperaldosteronism?

Answer 22

Adrenal tumour producing aldosterone
Not reported in dogs

Question 23

What are the clinical signs of hyperaldosteronism?

Answer 23

PUPD
Weakness
Neck ventroflexion (hypokalaemia)
Hypertension (sodium retention)

Question 24

How is hyperaldosteronism treated?

Answer 24

Restrict sodium and supplement potassium
Surgical excision
Spironolactone (aldosterone antagonist)

Question 25

Name the tumour of the adrenal medulla secreting catecholamines

Answer 25

Pheochromocytoma

Question 26

List the clinical signs of a Pheochromocytoma

Answer 26

Anxiety
Tachycardia
Tachypnoea
Vomiting
Diarrhoea
Weight loss
Hypertension (retinal detachment)

Question 27

How is a Pheochromocytoma diagnosed?

Answer 27

Radiography or ultrasound

Question 28

How is a Pheochromocytoma treated?

Answer 28

Radical excision (high risk), antihypertensive medication
Frequently metastasise