Hypoadrenocorticism Flashcards
What is the other name use for hypoadrenocorticism?
Addisons disease
What is the cause of hypoadrenocorticism?
Lack of mineralocorticoid and/or glucocorticoid secretion by the adrenal cortex
Describe primary hypoadrenocorticism
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
Describe secondary hypoadrenocorticism
Deficiency in ACTH secretion by the pituitary gland leading to atrophy of the adrenal cortices and decreased/absent glucocorticoid secretion. Mineralocorticoid secretion remains sufficient.
Describe the predispositions for hypoadrenocorticism
- 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
List the clinical signs of acute hypoadrenocorticism
- Severe depression/collapse
- Hypovolaemic
- Weak pulses
- Pale mm
- Bradycardic
- Dehydration
- Hypothermic
List the clinical signs of chronic hypoadrenocorticism
- Intermittent malaise
- Vomiting
- Diarrhoea
- Lethargy
- Weight loss
- Intermittent collapse
- Vague and intermittent
What is the cause of bradycardia in hypoadrenocorticism?
High potassium levels.
- Dehydration would normally cause tachycardia so the bradycardia suggests potassium levels have increased
Describe the haematology changes seen in hypoadrenocorticism
- 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
Describe the sodium and potassium changes seen in hypoadrenocorticism
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
Describe the main features of atypical Addisons
Cortisol deficiency
Normal Mineralocorticoids
Usually progress to mineralocorticoid deficiency
May have abnormal aldosterone stimulation
List the DDx for high potassium and low sodium levels
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
Describe the changes seen on the ECG of patients with Addisons
Bradycardia
Tall, narrow T waves
Prolonged QRS interval
Decreased P wave amplitude
Prolonged P-R interval
Absent P wave
Complete heart block
Ventricular arrhythmias
How can Addisons be detected on radiography?
Hypovolaemia signs: microcardia, reduced vascular pattern and a small vena cava
Which test can be used to rule out Addisons
Basal cortisol using a single ACTH stimulation test
Describe the results of the ACTH stimulation test in Addisons
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.
Describe fluid therapy for dogs with Addisons
- 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
Describe steroid treatment for acute Addisons patients
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
Describe steroid therapy for stabilised Addisons patients
Oral prednisolone
Fludrocortisone
What are the side effects of Addisons treatment?
Acute renal disease
Myelinosis
- Depression, weakness, ataxia, tetraparesis, and decreased sensory perception
- Signs occur days later and are often irreversible
Describe the prognosis of Addisons
Lifelong therapy
Add glucocorticoid when stressed
Normal life expectancy when treated and monitored correctly
What is the cause of hyperaldosteronism?
Adrenal tumour producing aldosterone
Not reported in dogs
What are the clinical signs of hyperaldosteronism?
PUPD
Weakness
Neck ventroflexion (hypokalaemia)
Hypertension (sodium retention)
How is hyperaldosteronism treated?
Restrict sodium and supplement potassium
Surgical excision
Spironolactone (aldosterone antagonist)
Name the tumour of the adrenal medulla secreting catecholamines
Pheochromocytoma
List the clinical signs of a Pheochromocytoma
Anxiety
Tachycardia
Tachypnoea
Vomiting
Diarrhoea
Weight loss
Hypertension (retinal detachment)
How is a Pheochromocytoma diagnosed?
Radiography or ultrasound
How is a Pheochromocytoma treated?
Radical excision (high risk), antihypertensive medication
Frequently metastasise
