Disorders of the Adrenal Gland Flashcards
Dr. Swan
What is the role of aldosterone in the adrenal cortex?
maintains extracellular fluid volume through its action on the DCT
conserves Na+ and wastes K+
What is the role of cortisol and corticosterone in the adrenal cortex?
- catabolism of proteins and amino acids
- antagonizes insulin and reduced glucose uptake
- gluconeogenesis
- glycogen storage in the liver
What are catecholamines produced from? Where in the adrenal gland?
tyrosine
adrenal medulla
Explain the RAAS system
What is the goal of the RAAS system regarding aldosterone?
preserve Na+
waste K+
What is the physiology of cortisol? Should be review lowkey
What is hyperadrenocorticism?
excessive circulating cortisol
Cushing’s
What are the forms of hyperadrenocorticism?
- iatrogenic
- spontaneous - primary and secondary
What is primary hyperadrenocorticism? How common?
functional adrenal neoplasia
15% canine
20% feline
What is secondary hyperadrenocorticism? How common?
pituitary dependent - microadenoma
85% canine
80% feline
What happens with hyperadrenocorticism - iatrogenic?
bilateral atrophy of both adrenal glands due to lack of ACTH stimulation
What does a functional adrenal neoplasia (primary) regarding hyperadrenocorticism look like?
unilateral mass
contralateral adrenal gland will be atrophied
What does a pituitary-dependent (secondary) regarding hyperadrenocorticism look like?
overproduction of ACTH due to lack of neoplastic cell response to serum cortisol
bilateral hypertrophy of adrenal cortex
MICROadenoma more common
What are some clinical signs of Cushing’s?
- polyuria
- polydipsia
- polyphagia
- pot-bellied appearance
- dermatopathy: (calcinosis cutis, ventral abdominal alopecia, hyperpigmentation)
- muscle weakness or wasting
- persistent or recurring infections
What are additional frequent physical exam findings regarding Cushing’s?
- hypertension - excess production of cortisol > increases blood pressure by enhancing sodium retention
- hepatomegaly - high cortisol levels lead to fat deposition in the liver (steatosis), promotes gluconeogenesis which can increase workload
What are CBC findings for hyperadrenocortisism?
- stress leukogram - leukoPENIA
- dehydrated (erythrocytosis, thrombocytosis)
What are chemistry findings regarding Cushing’s syndrome?
- increased ALP - dogs have an additional isoform, c-ALP [corticosteroid]
- mild hyperglycemia
- others in picture
Explain the characteristics of hyperadrenocorticism in cats
rare - pituitary-dependent most common (secondary)
cats are less sensitive to exogenous glucocorticoid administration, so iatrogenic is less frequent
What are clinical signs of hyperadrenocorticism in cats?
SKIN FRAGILITY!
- weakness
- abdominal distention
- lethargy
- weight loss
- GI signs
What is feline Cushing’s most commonly diagnosed with?
controlled or regulated diabetes mellitus
What are CBC findings in cats for hyperadrenocorticism?
What are chemistry findings in cats for hyperadrenocorticism?
T/F: There is no one diagnostic assay that diagnosis canine or feline Cushing’s disease
TRUE
What tests are used for Cushing’s test?
- dexamethasone suppression test (DDS) - low or high dose
- endogenous ACTH
- urine/serum cortisol
What tests for dogs do you do for Cushing’s?
low dose + endogenous ACTH (differentiate primary and secondary)
What tests for cats do you do for Cushing’s?
high dose + endogenous ACTH (differentiate primary and secondary)
How is urine/serum cortisol useful with Cushing’s syndrome?
urine cortisol to creatine ratio (UC:CR) or serum cortisol
- morning free catch urine sample
useful in ruling out possibility of Cushing’s disease only
What is the dexamethasone suppression test?
- pre-dexamethasone sample collected for basal cortisol
- 4 and 8 hours samples
What does this graph show with hyperadrenocorticism?
hyperadrenocorticism
- PDH or FAN
What does this graph show with hyperadrenocorticism?
hyperadrenocorticism
- iatrogenic or spontaneous
What does this graph show with hyperadrenocorticism?
uncommon escape pattern
adrenal hyperplasia due to PDH or a hyperresponsive adrenal gland because of a non-adrenal disorder
consider measurement of ACTH and ACTH stim test
What does this graph show with hyperadrenocorticism?
response of healthy dog or dog with non-adrenal disorder
What does endogenous ACTH test with hyperadrenocorticism?
does not diagnose but differentiates between pituitary-dependent & functional adrenal neoplasia
How do you prepare an endogenous ACTH sample?
frozen EDTA plasma sample sent to lab - ACTH not stable
In an endogenous ACTH test, what do you expect to see with pituitary-dependent hyperadrenocorticism?
ACTH within reference interval or increased
In an endogenous ACTH test, what do you expect to see with functional adrenal neoplasia hyperadrenocorticism?
ACTH decreased
T/F: Addison’s is easy to diagnose but difficult to determine when to screen
TRUE - resembles a lot of other diseases
What is primary hypoadrenocorticism?
autoimmune, immune-mediated destruction of the adrenal cortex
- typical
- atypical
iatrogenic - from over treatment of Cushing’s
What is typical primary hypoadrenocorticism?
commonly a deficiency in both glucocorticoids (cortisol) and mineralocorticoids (aldosterone)
What is atypical primary hypoadrenocorticism?
deficiency in glucocorticoids without deficiency in mineralocorticoids
detected earlier, not enough time to have destroyed zona glomerulosa
Primary or secondary hypoadrenocorticism more common?
primary
What signs can trigger hypoadrenocorticism?
stressful events
What are glucocorticoid signs of Addison’s?
anorexia
vomiting
lethargy/depression
What are mineralocorticoid signs of Addison’s?
shock-like state
- polyuria
- polydipsia
- collapse
- dehydration
- hypovolemic shock
Upon physical examination of a patient with Addison’s, what can you find?
BRADYcardia
hypovolemic shock - GI issues
**dogs with only a glucocorticoid deficiency may be unremarkable on PE
What on CBC do you see with a glucocorticoid Addison’s?
absence of a stress leukogram!!
- mild normocytic normochromic non-regenerative anemia
What on chemistry do you see with a glucocorticoid Addison’s?
- azotemia
- increased ALT
- hypocholesterolemia
What on CBC do you see with a mineralcorticoid Addison’s?
severe normocytic, normochromic anemia (blood loss anemia)
What on chemistry do you see with a mineralcorticoid Addison’s?
- hyperkalemia
- hyponatremia
- Na/K ratio <27: suspicious, <19 bad
What are diagnostic tests for Addison’s?
urine/serum cortisol
ACTH stimulation test
How does serum cortisol help with testing for Addison’s disease?
Addison’s patients will have a baseline or “resting” serum cortisol of <2 mcg/dL
a resting serum cortisol of >2 mcg/dL rules out Addison’s with nearly 100% confidence
A dog had a serum cortisol come back at <2 mcg/dL. Can we definitively say it is Addison’s?
NO - some dogs physiologically can have serum cortisol of <2 mcg/dL
How is a ACTH stim test for Addison’s performed?
at any time of day
basal cortisol sample taken before administration of ACTH
- ACTH administered
measured 1 hour later
An exaggerated response by ACTH stim test for Addison’s is considered at ______ ug/dL
18-22
Patient A was tested by ACTH stim test for Addison’s disease. Does this dog have it? If not, what else could it be?
does NOT
could be pituitary-dependent hyperadrenocorticism, functional adrenal neoplasia (hyperadrenocorticism), or a non-adrenal disorder
Patient B was tested by ACTH stim test for Addison’s disease. Does this dog have it? If not, what else could it be?
does NOT
healthy dog response
Patient C was tested by ACTH stim test for Addison’s disease. Does this dog have it? If not, what else could it be?
yes! - hypoadrenocorticism or iatrogenic hypoadrenocorticism
immune-mediated destruction or iatrogenic administration
- no adrenal cells there to release cortisol
Does the ACTH stim test rule out Cushing’s? Explain why
NO - because 16% of PDH and 49% of functional adrenal neoplasia cases have a response of a healthy dog!
What is hyperaldosteronism?
overproduction of aldosterone only
What is primary hyperaldosteronism?
conn’s syndrome - adrenal neoplasia is most common
What is secondary hyperaldosteronism?
excessive aldosterone due to activation of RAAS system generally due to congestive heart failure or chronic kidney disease
What is the characteristic sign of hyperaldosteronism?
cervical ventroflexion (total body depletion of potassium - hypokalemia)
What are other clinical signs of hyperaldosteronism?
weakness, difficulty jumping, hypertension, polyuria, polydipsia
What do you see on chemistry that indicates hyperaldosteronism?
marked hypokalemia (a lot of aldosterone will absorb Na+ but waste potassium)
- mild hypernatremia
- inadequate USG
Why should we not call it Equine Cushing’s?
hypercortisolemia is not typically a component of this disease
- adrenal glands are normal
What is Equine Pituitary Pars Intermedia Dysfunction characterized by?
pituitary adenomas of the pars intermedia
melanotrophs overproduce and secrete - POMC, etc
What is pathognomonic to Equine Pituitary Pars Intermedia Dysfunction?
hirusitism (hypertrichosis)
What are the clinicopathologic findings to Equine Pituitary Pars Intermedia Dysfunction?
- hyperglycemia
- hyperinsulinemia
- hypertriglyceridemia
- high fecal egg count
In horses ______ secretion is seasonal
ACTH (why hypertrichosis being present in the winter is a prominent sign)
What is hyperadrenocorticism in ferrets?
overproduction of androgens - can lead to aplastic anemia
What is a very common sign of ferret hyperadrenocorticism?
bilateral alopecia
