Endocrinology - Hypoadrenocorticism Flashcards
What are the regions of the adrenal cortex?
Zona glomerulosa, zona fasciculata, and zona reticularis
What does the zona glomerulosa secrete?
mineralocorticoids - think salt
What does the zona fasiculata secrete?
glucocorticoids - think sugar
What does the adrenal medulla secrete?
catecholamines
What does a deficiency in aldosterone (mineralcorticoid) result in?
Hypoadrenocorticism (Addison’s disease)
What does an excess of cortisol (glucocorticoid) result in?
Hyperadrenocorticism (Cushing’s)
What does a deficiency in cortisol (glucocorticoid) result in?
Hypoadrenocorticism (Addison’s disease)
What stimulates the production and release of glucocorticoids from the adrenal cortex?
ACTH
What provides negative feedback on the pituitary gland to stop secreting ACTH?
Cortisol
What provides negative feedback on the hypothalamus to stop secretion of CRH?
ACTH and cortisol
What are the actions of glucocorticoids?
Antagonize the effects of insulin, stimulate appetite, maintain normal blood pressure/vascular tone, and maintain normal GI perfusion, motility, and mucosal integrity
If there is a deficiency in glucocorticoids, what is the consequence of the decreased antagonistic effect on insulin?
hypoglycemia
If there is a deficiency in glucocorticoids, what is the consequence of decreased appetite stimulation?
anorexia
If there is a deficiency in glucocorticoids, what is the consequence of decreased BP/vascular tone maintenance?
hypotension
If there is a deficiency in glucocorticoids, what are the consequences of altered maintenance in GI perfusion, motility, and mucosal integrity?
Vomiting, diarrhea, and weight loss
What is aldosterone secreted in response to?
Hyponatremia, hypotension, hypovolemia, hyperkalemia, and ACTH (minor role)
What chemical stimulates aldosterone secretion and from where is aldosterone secreted?
Angiotensin; aldosterone is secreted from the adrenal glands
How does aldosterone correct a drop in ECF/Na/BP?
It stimulates renal sodium conservation so that water is passively reabsorbed with sodium and the net result is an increase in ECF volume
How does aldosterone correct hyperkalemia?
It stimulates renal potassium excretion which results in blood K levels to decrease
What are the actions of aldosterone?
Renal excretion of potasisum, renal conservation of sodium, and renal excretion of hydrogen ions
If there is a deficiency in aldosterone, how is renal excretion of potassium effected?
hyperkalemia
If there is a deficiency in aldosterone, how is renal conservation of sodium effected?
Hyponatremia (+PU/PD)
If there is a deficiency in aldosterone, how is renal excretion of hydrogen ions effected?
Metabolic acidosis
What are the two forms of hypoadrenocorticism?
Primary and secondary
What is affected in primary hypoadrenocorticism?
the adrenal gland
What is affected in secondary hypoadrenocorticism?
the pituitary gland
Is primary or secondary hypoadrenocorticism more common?
primary
What physiologically causes primary hypoadrenocorticism?
There is a loss of functional adrenal cortical tissue - 85-90% loss before CS
What physiologically causes secondary hypoadrenocorticism?
Loss of ACTH stimulation to the adrenal gland
What are the two main etiologies of primary hypoadrenocorticism?
Immune-mediated disease and idiopathic atrophy and fibrosis
There are many other causes - basically anything that can injure the adrenal gland in any way can be a cause
Typically, are males or females more prone to getting primary hypoadrenocorticism?
Females
Typically, what breed of dogs are more prone to getting primary hypoadrenocorticism?
Mixed medium to larger breed dogs
Typically, at what age is primary hypoadrenocorticism diagnosed?
at a younger age
What breed of dogs possibly have a genetic predisposition to acquiring primary hypoadrenocorticism?
Standard poodle, portugese water dog, Nova Scotia duck tolling retriever, and Bearded collies
Hypoadrenocorticism has no pathognomonic signs which is why it is known as the ______ _______.
great imitator
What PE exam findings are consistent with hypoadrenocorticism?
Dehydration, bradycardia, poor peripheral pulse quality, melena/hematochezia, hypothermia, and abdominal pain (rare)
What CBC findings are consistent with hypoadrenocorticism?
Lack of a stress leukogram, eosinophilia, and lymphocytosis
What chemistry findings are consistent with hypoadrenocorticism?
Hypoglycemia, hyperkalemia, hyponatremia, metabolic acidosis, azotemia, hypocholesterolemia, hypoalbuminemia, and hypercalcemia
What does a stress leukogram look like?
Segs Monocytes Increased Lymphocytes Eosinophils Decreased
What is a classic finding (chemistry) in cases of hypoadrenocorticism?
Combined hyponatremia and hyperkalemia as the result of aldosterone deficiency
How is hypoadrenocorticism diagnosed?
ACTH stimulation test
What is the procedure for a ACTH stimulation test?
Collect baseline serum cortisol, then administer ACTH, and then collect a second serum cortisol sample an hour after cortisol administration
What will the result of ACTH stimulation test be in a healthy dog? An addisonian dog?
In a healthy dog, the post cortisol level should be elevated. In an addisonian dog, the cortisol level will remain the same.
What does the ACTH stimulation test test for?
adrenal reserve
What will an exaggerated cortisol increase after ACTH indicate?
Hyperadrenocorticism (Cushing’s)
What basal cortisol level helps rule out hypoadrenocorticism?
a level of >2.0 micrograms/dl
What can interfere with an ACTH stimulation test?
Exogenously administered steroids because they can suppress normal adrenal glands or cross-react and be measured as cortisol
How is hypoadrenocorticism treated?
Hormone replacement therapy - Glucocorticoids or mineralcorticoids
When using glucocorticoid replacement therapy for hypoadrenocorticism treatment, what should you inform the clients about?
Make sure they know the clinical signs associated with deficiency and excess glucocorticoids
What are the injectable forms of mineralcorticoid hormone replacement?
Percortin or Zycortal
What is the oral form of mineralcorticoid hormone replacement?
Florinef
When should you recheck a patient after starting treatment for hypoadrenocorticism?
10-14 days and 25-28 days
What should be done at the 10-14 day recheck in an Addisonian patient?
Weight, physical exam, renal panel, and electrolyte levels
What should be done at the 25-28 day recheck in an Addisonian patient?
Weight, physcial exam, renal panel, electrolyte levels - redose DOCP
When adjusting mineralcorticoids at recheck appointments, what dose should you adjust to?
The lowest dose or the longest interval that keeps electrolytes normal
When adjusting prednisone at recheck appointments, what dose should you adjust to?
you want to adjust it to as needed based on clinical response
What is an Addisonian crisis?
Severe, acute manifestation of hypoadrenocorticism
What clinical manifestations are associated with an Addisonian crisis?
Hypotension, hypovolemia, electrolyte imbalances, hypoglycemia, and severe GI signs
What is the most important treatment for patients in an Addisonian crisis?
IV fluids
What other treatments should be done in patients with Addisonian crisis?
Dextrose if the patient is hypoglycemic, emergency management of hyperkalemia, symptomatic supportive care, and address any complicaitons
In patients in Addisonian crisis, when is glucocorticoid replacement given?
Ideally once the ATCH stimulation test is complete
When is it indicated to use dexamethasone in patients in Addisonian crisis/
It should be used if glucocorticoids must be given prior to completion of ACTH stimulation test
What is the prognosis for patients with hypoadrenocorticism?
Excellent with committed owners but it can be expensive
What is ‘atypical’ Addison’s disease?
Glucocorticoid deficiency only with normal electrolytes and mineralcorticoid levels
What clinical signs are associated with atypical addisonian disease?
GI signs and decreased appetitie
How is atypical addisonian disease diagnosed?
ACTH stimulation test and normal electrolyte levels
What is the therapy of choice for atypical addisonian disease?
glucocorticoid replacement
