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Endocrine Pathophysiology > Pathophysiology of the Adrenal Glands: Diagnostics and Cases > Flashcards

Pathophysiology of the Adrenal Glands: Diagnostics and Cases Flashcards

1
Q

what are some tests to screen for adrenocortical diseases?

A

baselines cortisol level
urine cortisol:creatinine ratio
function tests

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2
Q

what are some function tests for screening for adrenocortical diseases?

A

ACTH stimulation test
low-dose dexamethasone suppression test
TRH stimulation test: equines only

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3
Q

what are some tests to test for the etiology of adrenocortical diseases?

A

high-dose dexamethasone suppression test
endogenous ACTH level
advanced imaging

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4
Q

what is the secretion of ACTH and cortisol like?

A

pulsatile

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5
Q

is basal cortisol useful for diagnosis of hyperadrenocorticism?

A

no: while cushing’s causes excess levels of cortisol, single baseline cortisol often falls in the normal range

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6
Q

what can high-normal basal cortisol rule out?

A

hypoadrenocorticism

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7
Q

what is urine cortisol:creatinine ratio used to rule out?

A

hyperadrenocorticism

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8
Q

what is the test of choice for diagnosing hypoadrenocorticism?

A

ACTH stimulation test

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9
Q

what should cause an exaggerated response to ACTH stimulation?

A

cushing’s
no longer recommended to diagnose cushing’s

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10
Q

what is the ACTH stimulation test like?

A

relatively specific: 15% false positives
not very sensitive
positive test does not indicate etiology

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11
Q

how do you perform a low-dose dexamethasone suppression test?

A

give dexamethasone and measure cortisol

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12
Q

what does a low-dose dexamethasone suppression test evaluate?

A

responsiveness of pituitary to physiologic levels of negative feedback

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13
Q

is a low-dose dexamethasone suppression test used to diagnose addison’s?

A

no

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14
Q

how sensitive is a low-dose dexamethasone suppression test?

A

very sensitive: 98% in dogs
90% in cats
not used in horses due to fear of developing laminitis

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15
Q

what cortisol concentrations do healthy dogs have at 8 hours with a low-dose dexamethasone suppression test?

A

<1.4 micrograms/dL

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16
Q

a high-dose dexamethasone suppression test should not be performed on animals in which _______________________________

A

the clinical diagnosis is uncertain

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17
Q

how many canine pituitary tumors do not suppress with high-dose dexamethasone suppression test?

A

25-30%

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18
Q

what can an endogenous ACTH level be used to help determine?

A

cause of hyperadrenocorticism
cause of hypoadrenocorticism

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19
Q

what can resting ACTH be a good screening test for in horses?

A

equine pituitary pars intermedia dysfunction
horses with PPID have higher ACTH values than normal horses

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20
Q

what can thyrotropin releasing hormone stimulation test be used to diagnose in horses?

A

early equine pituitary pars intermedia dysfunction

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21
Q

who produces POMC?

A

corticotrophs in pars distalis and melanotrophs in pars intermedia

22
Q

what is the procedure of a TRH stimulation test?

A

measure basal ACTH level
measure ACTH 10 minutes after administration of thyrotropin releasing hormone

23
Q

what are some causes of hypercholesterolemia?

A

hyperadrenocorticism
hypothyroidism
liver disease with cholestasis
nephrotic syndrome
diabetes mellitus
pancreatitis

24
Q

in hyperadrenocorticism, who is increased ALP activity seen in?

A

dogs

25
Q

is urine cortisol:creatinine ratio a screening or diagnostic test?

A

screening: if consistent with hyperadrenocorticism, need to further work up

26
Q

true/false: a “normal” ACTH stimulation test does not rule out hyperadrenocorticism

A

true

27
Q

what pattern with the LDDS test indicates a pituitary-dependent hyperadrenocorticism?

A

cortisol <1.4 micrograms/dL at 4 hours
>1.4 at 8 hours

28
Q

in a high dose dexamethasone suppression test, does failure to suppress rule out a pituitary tumor?

A

no: not diagnostic for hyperadrenocorticism due to adrenal tumor

29
Q

if a test is highly sensitive, a negative test is _______________________

A

extremely useful

30
Q

if a test is highly specific, a positive test is _________________________

A

extremely useful

31
Q

is basal cortisol a useful test for diagnosis of hyperadrenocorticism?

A

no
single baselines cortisol often falls in the normal range

32
Q

what can high-normal basal cortisol rule out?

A

hypoadrenocorticism

33
Q

why are false positives of urine cortisol:creatinine ratio common?

A

chronic stress/disease

34
Q

why is an ACTH stimulation test no longer indicated for diagnosing Cushing’s?

A

may miss the diagnosis of early pituitary dependent hyperadrenocorticism if adrenal hyperplasia has not yet occurred
changes happen over time

35
Q

does a low-dose dexamethasone suppression test provide etiology?

A

maybe

36
Q

in a low-dose dexamethason suppression test, healthy dogs have cortisol concentrations of ______________ at 8 hours

A

<1.4 micrograms/dL

37
Q

animals with PDH would have cortisol levels _________________ at 4 or 8 hours with a high-dose dexamethasone suppression test

A

<1.4 micrograms/dL
adrenal tumor stays high

38
Q

which canine pituitary tumors do not suppress with high-dose dexamethasone suppression test?

A

pars intermedia tumors lack portal blood supply
large, poorly differentiated pars distalis tumors

39
Q

do you need to determine etiology for horses with cushing’s?

A

no

40
Q

what would you expect the endogenous ACTH level to be in an animal with an adrenal tumor causing hyperadrenocorticism?

A

<20 pg/mL
low

41
Q

what would you expect the endogenous ACTH level to be in an animal with PDH?

A

normal to elevated
<20, 20-45, >45 pg/mL

42
Q

what is endogenous ACTH level a good screening test for?

A

equine pituitary pars intermedia dysfunction

43
Q

what levels of endogenous ACTH do horses with pituitary pars intermedia dysfunction have?

A

higher

44
Q

what is the seasonal variation of endogenous ACTH in horses?

A

Nov-July: <15 pg/mL
Aug-Oct: <30 pg/mL

45
Q

what does the endogenous ACTH level test use for a tube?

A

EDTA plasma
plastic
cold or frozen

46
Q

what are the differentials for a Na/K ratio < 25 or 22?

A

hypoadrenocorticism
renal disease
ruptured bladder
diabetes with ketoacidosis
severe diarrhea

47
Q

what are some causes of hypoglycemia?

A

hypoadrenocorticism
artifact: metabolized by red blood cells
hyperinsulinism
sepsis/endotoxemia
underproduction of glucose

48
Q

what are some causes of increased alkaline phosphatase activity?

A

cholestasis
bone isoenzyme
drug induction
cortisol induced production of isoenzyme: dogs

49
Q

what are some causes of hypercholesterolemia?

A

hyperadrenocorticism
hypothyroidism
liver disease with cholestasis
nephrotic syndrome
diabetes mellitus
pancreatitis

50
Q

does failure to suppress during a high-dose dexamethasone suppression test rule out a pituitary tumor?

A

no

Endocrine Pathophysiology (6 decks)

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