Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

VETM 442 > Thyroid and Pituitary > Flashcards

Thyroid and Pituitary Flashcards

1
Q

which is the major product f the thyroid, T4 or T3?

A

T4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

true or false: T3 and T4 are not protein bound and there is lots of free active hormone in the blood

A

false! almost 99% of T3 and T4 are protein bound and there is very little free active hormone in the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

only _____ can enter the cells and carry out the role of increasing metabolism

A

free T4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

hypothyroidism is most common in _____, and most cases are due to _______ hypothyroidism

A

dogs, primary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

in dogs, primary hypothyroidism can be what two things?

A
  • idiopathic atrophy of the thyroid gland
  • immune mediated destruction–>autoantibodies
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

secondary hypothyroidism means that

A

the pitutary is injured or not working and is not releasing TSH, this is rare

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the common CBC findings for a hypothyroid dog?

A
  • mild normocytic normochromic non regenerative anemia–>decreased metaboli rate means decreased oxygen demand in tissues, leads to decreased EPO production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are common biochemistry findings fo a dog with hypothyroidism?

A
  • moderate to marked hypercholesterolemia–>especially in a fasted sample!!!
  • mildly increased ALP and ALT, possible mild cholestasis, uncertain why this happens
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

hyperthyroidism is most common in _____, and most of the time it is caused by

A

cats
benign multinodular adenomatous hyperplasia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are some common CBC findings in a cat with hyperthyroidism?

A
  • mild to moderate erythrocytosis–>possible stimulation of EPO due to increased oxygen demeand of tissues from increased metabolic rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are some common biochem findings for a cat with hyperthyroidism?

A
  • mild to moderate increase in ALP–>due to increased bone and liver ALP isoenzymes and increased bone metabolism
  • moderate to marked increase in ALT–>uusally WITH the high ALP, this will hapen in 90% of cases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

a cat comes to you super skinny, poor hair coat, and it has a thyroid slip. On biochem you see the ALT and ALP are higher than 500. What does this mean?

A

hyperthyroid cats can have a high ALT and ALP, but not that high. I would investigate for other causes or other concurrent diseases if they are this high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the most common way to test for hypothyroidism? what are some things to think about with this test?

A
  • a serum total T4 test, which is a sum of protein bound and free hormone
  • this test can be affected by presence of T4 autoantibodies, aka it can be affected by concurrent non-thyroid illness
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why is a free T4 test better than a serum total T4 test?

A
  • it tests the unbound, biologically active form of T4
  • it is the most accurate test for dogs
  • it is NOT affected by autoantibodies
  • it is NOT affected by concurrent illness as total T4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

the TSH test is only done in ____, and it is used to confirm….

A

dogs
used to confirm hypothyroidism in conjunction with serum or free T4, but dogs with hypothyroidism won’t alaways have a high TSH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

the biggest confounding factor in diagnosis of hypothyroidism is

A

differentiating hypothyroidism from euthyroid sick syndrome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is euthyroid sick syndrome?

A

suppression of the thyroid hormone in dogs in response to concurrent illness happening elsewhere in the body, to decrease metabolism in times of illness. this can cause the T4 to be low and it can look like hypothyroidism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what are the typical “textbook” thyroid pannel results from a dog with hypothyroid?

A
  • decreased serum T4, decreased free T4, increased TSH, WITH CLINICAL SIGNS!!!
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

true or false: if a dog’s serum T4, free T4, and TSH are all normal, you can rule out hypothyroidism

A

true

20
Q

when testing for hypothyroidism…
- the closer the T4 is to the normal range, the more likely…..
- the lower the total T4,, the more likely…

A

the dog is euthyroid and not hypothyroid
the dog is hypothyroid and not euthyroid–>assuming clinical signs and no other euthyroid illness signs are present

21
Q

if you get a low T4 result but you don’t suspect hypothyroid, wha are three things you should consider?

A
  • euthyroid sick syndrome: look for underlying illness
  • drugs may cause it, like steroids or phenobarb, etc
  • certain breeds can have this: sighthounds like greyhounds
22
Q

what test reliably confirms diagnosis of hyperthyroidism in cats?

A

increased total T4

23
Q

what could you do if you had a cat that really looks like it has hyperthyroid but the T4 isn’t increased…?

A

re test in 1-2 weeks, or do a free T4 test

24
Q

true or false: i can use a free T4 test alone to diagnose hyperthyroidism in cats

A

false! 20-30% cats sick with euthyroid have flase positive free T4 tests. The free T4 test for cats is better used in concert with the total T4 test in conjunction with clinical signs

25
Q

say you had a skiny cat with a palpable thyroid and you have the following test result for total T4: 70mmol/L. conclusion?

A

it’s more than 65 so YEP YOU GONNA SEE IT ITS HYPERTHYROID

26
Q

say you had a skiny cat with a palpable thyroid and you have the following test result for total T4: 55mmol/L. conslusion??

A

hmmmm it’s not higher than 65, I would retest in a few weeks or do a free T4 test

27
Q

since hyperthyroidism is not common in dogs, if a dog has a high T4, what could cause this?

A
  • thyrozine treatment/hypothyroid treatment
  • anti T4 antibodies
  • thyroid mass
  • dietary influences like with raw feeds containing thyroid
  • very rarely, primary hyperthyroidism
28
Q

hyperadrenocorticism is a disease common in ____, most often caused by

A

dogs
- pitutary dependent hyperadrenocorticism (80% of cases), excess ACTH
- functional adrenal neoplasia (10-15% cases), excess cortisol
- iatrogenic from steroids

29
Q

common clinical signs of cushings in dogs include

A
  • PU/PD, polyphagia, abdominal enlargement, bilateral alopecia, calcinosis cutis/crusties, muscle weakness, panting
30
Q

why are cushings dogs PUPD? why do they have muscle weakness? why do they have big bellies? why do they have skin changes?

A
  • a decrease in ADH from hypothlamus and decreased renal tubular sensitivity to ADH
  • increased protein catabolism and muscle wasting
  • fat in abdomen, hepatomegaly
  • hair follicle atrophy
31
Q

what are some classic CBC findings of a cushings dog?

A
  • stress leukogram: neutrophilia, monocytosis, lymphopenia, eosinopenia
  • thrombocytocic: not sure why this happens?
32
Q

what are some classic biochem findings in. dog with cushins?

A
  • really high ALP*** 90-95% of cases
  • mild increase in ALT–>secondary to swollen hepatocytes/glycogen accumulation?
  • high cholesterol, triglycerides, lipemia
  • hyperglycemia: from an increase in gluconeogenesis in liver
  • **normal BUN and creatinine even with isosthenuria or hyposthenuria
33
Q

classic findings on a urinalysis of a dog with cushings?

A
  • USG low, less than 1020, can be lowerthan 1007 due to ADH interference from cortisol
  • mild proteinuria: mild protein losing
  • inactive urine sediment –>but remember UTIs concurrently are common
34
Q

true or false: sometimes cushings dogs can have a low T4

A

true, need to treat the cushings first and then re test thyroid after

35
Q

true or false: you can tell between pituitary and functional adrenal dependent cushings based on clinical signs

A

NO FALSE! you need testing

36
Q

why should you find out if the dog has PDH or FAN?

A

it affects treatment and prognosis

37
Q

which tests can you use for SCREENING for cushings (not for finding out if it’s PDH or FAN, just if they have it in general)

A
  • BCB, biochem, UA
  • LDDST
  • ACTH stim
  • urine cortisol:creatinine ratio
38
Q

what are the descriminating tests to use for cushings, aka, which tests can you use to determine if its PDH or FAN?

A
  • LDDST
  • HDDST
  • endogenous ACTH
  • US
  • CT/MRI
39
Q

briefly describe how a LDDST works?

A
  • blood serum collected for initial oncentration
  • give a low dose of dexamethasone, 0.01mg/kg IV
  • measure cortisol 4 hours and 8 hours later

in healthy dogs, the dex will inhibit pituitary secretion of ACTH which should decrease cortisol secretion for up to 48 hours, usually less than 40mmol/L

40
Q

in a case of suspected cushings, how should you approach a LDDST?

A
  • first, look at the 8 hour concentration, and if it is more than 40, it is consistent with cushings and there is no evidence of suppression
  • second, see if you can differentiate between PDH and FAN. With FAN, there will be NO suppression AT ALL. If it’s PDH, you might see: less than 40 or less than half the baseline at 4 hours, or less than half of baseline but greater than 40 at 8 hours
41
Q

what is the primary use of a HDDST? How does it normally work?

A
  • to differentiate between PDH and FAN if results from LDDST don’t give you much
  • only change from LDDST is the dose, goes up to 0.1mg/kg IV
  • in normal dogs: ACTH release is inhibitied for 24-48 hours, cortisol usually less than 40 at 4 and 8 hours
42
Q

in a dog with PDH, how will the HDDST test appear?

A

in 60-75% of PDH cases, there will be suppression at 4 and/or 8 hours

43
Q

what is an endogenous ACTH test used for and how does it normally work?

A
  • used as descriminating test
  • with PDH, it will be normal to high ACTH
  • with FAN, it will be low ACTH

***BUT remember ACTH secretion is episodic, so if it’s high it means you have PDH but if ACTH is low, could be either PDH or FAN….

44
Q

what is an ACTH stim test used for and how does it normally work?

A
  • get a serum sample beforehand, then give synthetic ACTH, then take a sample 1 hour afterwads and measure cortisol
  • this is a screening test, doesn’t help you tell between PDH or FAN
  • in cases of both PDH and FAN: post ACTH cortisol should be more than 550–>super sensitive to ACTH
  • normal dogs should be below 470-500
45
Q

what is the best test to use to identify iatrogenic cushings? what result would you see?

A

ACTH stim test
chronic steroids cause adrenocortical atrophy and a blunted response to ACTH, so it will be very low, no response at all basically

46
Q

which is sensitive and which is specific: LDDST and HDDST

A

sensitive: LDDST
specific: HDDST

47
Q

why is ALP increased in a dog with cushings?

A

too much cortisol causes increased lipolysis and induction of ALP (mostly the C-ALP isoform in dogs)

VETM 442 (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions