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RUSVM Clinical Pathology > Endocrine > Flashcards

Endocrine Flashcards

1
Q

T/F: no single test definitively diagnoses hypothyroidism

A

True

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2
Q

Ectopic thyroid tissue often localized in what areas?

A

Cervical

Mediastinum

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3
Q

Secretion and regulation of thyroid hormone is regulated by ?

A

TSH

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4
Q

What is the biologically active form of thyroid hormone?

A

Unbound

Enters cells -> bind receptors -> initiates changes

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5
Q

What are the effects of thyroid hormone?

A

CATABOLIC!

Increase metabolic rate 
Increase O2 consumption 
Stimulate erythropoiesis 
positive inotrope and chronotrope 
Catabolizes muscle and adipose tissue 
Alters lipoprotein metabolism
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6
Q

What are the 3 main thyroid function tests?

A 
Total thyroxine (TT4)
Free thyroxine (FT4) 
Thyroid stimulating hormone (TSH)
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7
Q

What thyroid panel is usually run in dogs?

A 
Total thyroxine (TT4) 
Free thyroxine (FT4) 
Thyroid stimulating hormone (TSH)
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8
Q

What thyroid panel is usually run in cats?

A

Total thyroxine (TT4) only required*

Can run free thyroxine (FT4)

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9
Q

What is the gold standard for TT4?

A

Radioimmunoassay (RIA)

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10
Q

How does a radioimmunoassay function?

A

Known amountof T4 Ab is mixed with T4*(radiolabelled)

Serum is mixed with the Ab-T4*

T4 in serum will displace the Ab from T4*
T4-Ab complexes are measured for radioactivity

High radioactivity -> less serum T4
Low radioactivity -> more serum T4

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11
Q

What two assays measure unbound T4

A 
Equilibrium dialysis (ED)- gold standard 
Radioimmunoassya (RIA)
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12
Q

What three assays are used to measure TSH?

A

Immunoradiometric
Chemiluminescent
ELISA

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13
Q

T/F: Assays measuring TSH are efficient at detecting both high a low concentrations of TSH

A

FALSE

Cannot detect low [TSH]
-> in hyperthyroid cats, dont bother running this because values of TSH will be too low to be detected

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14
Q

What are the two major disease syndromes of canine hypothyroidism ?

A

Primary - autoimmune disease

Secondary - pituitary gland neoplasia/congenital malformation/ trauma/surgery

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15
Q

Primary hypothyroidism results form???

A

Lymphocytic thyroiditis -> idiopathic thyroid atrophy

Thyroglobulin auto-antibodies (TGAA)
Lymphocytes and macrophages
Fibrous tissue

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16
Q

Clinical signs associated with hypothyroidism?

A

Fat, sleepy, lethargic, metal dullness
Weight gain

Cold intolerant

Bradycardia

Skin lesions: alopecia, increased shedding, poor hair coat

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17
Q

What may you see on a CBC in a dog that has hypothyroidism ?

A

Mild to moderate non-regenerative anemia

-decreased metabolic rate -> decrease O2 demand -> decreased EPO

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18
Q

What is the most common chemistry abnormality associated with canine hypothyroidism ?

A

Hypercholesterolemia

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19
Q

TT4 decreased
FT4 decreased
TSH incresed

A

Primary hypothyroidism

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20
Q

TT4 decreased
FT4 decreased
TSH decreased

A

Secondary hypothyroidism

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21
Q

What is the DDx for a decreased TT4?

A

Hypothyroid
Euthyroid sick syndrome
Spurious

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22
Q

What is euthyroid sick syndrome

A

Adaptive response to illness.

Absent clinical signs for hypothyroidism

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23
Q

TT4 decreased
FT4 normal
TSH normal

A

Euthyroid sick syndrome

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24
Q

What is the most common endocrine disorder of cats?

A

Hyperthyroidism

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25
Q

What is the pathogenesis of feline hyperthyroidism?

A

Functional adenoma (hyperplasia)

Over production of thyroid hormone

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26
Q

Clinical signs associated with hyperthyroidism

A 
Palpable thyroid slip 
Tachycardia 
Polyphagia 
Hyperactivity 
Diarrhea
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27
Q

What may you expect to see on a CBC of a hyperthyroid patient?

A

Polycythemia

  • increased metabolic rate -> increase O2 demand -> increased EPO
  • T4 directly stimulates BM erythropoiesis

Heinz body formation

Stress leukogram

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28
Q

T/F: increases with ALT can be associated with hyperthyroidism

A

True

-severity correlates with TT4 levels

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29
Q

How does hyperthyroidism mask azotemia

A

Increased GFR due to increased cardiac output
Less muscle mass -> lower basal CREA

Will be unmasked with hyperthyroidism is treated!

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30
Q

What is the single, reliable test for diagnosing feline hyperthyroidism ?

A

Total T4

Will be increased (duh)

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31
Q

What is the most common chemistry abnormality associated with feline hyperthyroidism ?

A

Hypocholesterolemia

32
Q

Parathyroid hormone is produced by the _________cells

A

Chief

33
Q

Primary hyperparathyroidism will cause what to the Ca and Phos?

A

Increase Ca

Decrease Phos

34
Q

What does hypoparathyroidsim cause to the Ca and Phos?

A

Decreased Ca

Increased Phos

35
Q

Is primary hyperparathyroidism usually a adenoma or carcinoma ?

A

Adenoma

36
Q

What are your top DDx for hypercalciemia?

A

Lymphoma
Perianal gland adenocarcinoma
Mammary carcinoma
HyperPTH

Hypoadrenocorticism 
Renal secondary hyperparathyroidism 
Vit D toxicosis 
Granulomatous inflammation 
Osteolytic disease 
Thiazide diuretic/toxin
37
Q

Ca increased
Phos decreased
PTH increased
PTHrp zero

A

Primary hyperPTH

38
Q

Ca High
Phos Low
PTH in reference range
PTHrp zero

A

Primary hyperPTH

39
Q

Ca low
Phos high
PTH low
PTHrp zero

A

Primary hypoPTH

40
Q

What are the two types of diabetes insipidus ?

A 
Central DI (CDI) - deficiency of ADH
Nephrogenic DI (NDI)- no response to ADH
41
Q

In health, how does ADH regulate water balance?

A

ADH binds to receptor
Upregulate cAMP
AQP transported to cell membrane
H20 resorption

42
Q

What will the USG be in a patient with DI?

A

Isosthenuric or hyposenuric

43
Q

What is the other DDx you may have along with DI?

A

Psychogenic polydipsia

44
Q

How are CDI and NDI differentiated?

A

ADH response test

Water deprivation test -DANGER DONT DO THIS
Modified water deprivation test

45
Q

What is the ADH response test?

A

Administer desmopressin

  • > if USG increase -> central DI
  • > if USG is still low -> nephrogenic DI
46
Q

What is the theory behind the water deprivation test?

A

Dehydrate animal
Does the animal release ADH and concentrate urine?
Yes-> psychogenic PD
No-> DI

47
Q

What are the three forms of canine hyperadrenocorticism (HAC)

A

Pituitary-dependent hyperadrenocorticism (PDH)
Functional adrenal tumor (AT)
Iatrogenic

48
Q

What is the most common form of canine hyperadrenocorticism

A

Pituitary tumor -> produce high levels of ACTH -> bilateral adrenal hypertrophy -> negative feedback ineffective

49
Q

What is the pathogenesis of adrenocortical tumor leading to hyperadrenocortism

A

adrenal tumor constantly produce cortisol -> feedback to pituitary -> no ACTH production -> atrophy of other gland

50
Q

What is the pathogenesis of iatrogenic hyperadrenocortisim?

A

Steroids animinstered -> constant negative feedback to pituitary -> no ATCH produced -> atrophy of both adrenal glands

** this is why we taper off of glucocorticoids **

51
Q

Clinical signs associated with hyperadrenocorticism

A 
PU/PD/PP
Pot-bellied appearance 
Panting 
Muscle and ligament weakness 
Alopecia 
Calcinosis cutis 
Cutaneous hyerpigmentation
52
Q

What CBC and Biochemical changes would you see with hyperadrenocortism?

A

Stress leukogram

Increase ALP
Increase ALT
Increase Cholesterol

53
Q

What will the USG be in a cushings dog ?

A

Low (1.004-1.020)

54
Q

T/F: UTIs can commonly be associated with HAC

A

True

Steroids increase insulin resistance -> glucosuria -> bacterial infection

55
Q

Why do we need to differentiate between pituitary-dependent and primary adrenal tumors?

A

Different therapies!

Pituitary -> medically managed

Adrenal -> surgery possible

56
Q

What are the screening tests for HAC?

A

ALP activity
Urine cortisol: creatinine ratio (UCCR)

Not specific for HAC

57
Q

What test do you use to confirm HAC

A

Low dose desamethasone suppression test (LDDST)

58
Q

LDDST

Serum cortisol decreases. What does this mean?

A

Healthy dog

Steroid -> neg feedback on pituitary -> pituitary secretes LESS ACTH -> lower cortisol

59
Q

T/F: with a LDDST test in a dog with a pituitary tumor, will result in suppression of cortisol

A

False

Cortisol will remain high

60
Q

LDDST test

At 8hrs, cortisol is increased

At 4hrs, cortisol is increased

What this this

A

HAC - could be pituitary or adrenal

61
Q

LDDST test

At 8hrs, Increased cortisol

At 4hrs, decreased cortisol

A

Pituitary dependent HAC

an adrenal tumor will NEVER have suppression with steroid admin, can sometimes occur with LDDST

62
Q

What is the ACTH stimulation test? When do we use it?

A

Administer ACTH -> in healthy dog should result in cortisol increase

Used in patient with concurrent non-adrenal disease
Only test that will identify iatrogenic HAC

63
Q

ACTH stimulation test

No increase in serum cortisol

A

Iatrogenic HAC

64
Q

ATCH test

Serum cortisol is significantly increased. (>20ug/dL)

A

HAC

Hypersecreted cortiosl when given ACTH

65
Q

About 30% of dogs with pituitary tumors do not suppress with either LDDST or HDDST. In these cases, what test to we use to differentiate adrenal tumors from pituitary tumors?

A

Measure ACTH

66
Q

In a ACTH concentration test, if [ACTH] is increased/normal it is _______ HAC, but if the [ACTH] is decreased it is a _______ HAC

A

Pituitary-dependent (intermittently secrete ATCH)

adrenal tumor (negative feedback of cortisol from tumor lowers ACTH)

67
Q

Hypoadrenocorticism usually affects what dogs?

A

Females
Young and middle aged
Mixed breed most prevalent

68
Q

What is a primary vs secondary hypoadrenocorticism ?

A

Primary- immune mediated destruction of adrenal cortices

Secondary- destructive lesions in hypothalamus or pituitary resulting in less CRH or less ACTH

69
Q

Hypoadrenocorticism causes what hormonal imbalances

A

Low Aldoserone -> loss of Na and water and retention of K+

Low cortisol

70
Q

Clinical signs associated with hypoadrenocorticism

A 
Poor appetite 
Lethargy 
Thin 
Vomiting
Weakness
71
Q

Clinical signs associated with hypovolemic crisis (aka addisonian crisis) ?

A

Dehydration
Shock
Bradycardia (due to hyperkalemia)
Weak femoral pulse

Melena

72
Q

What may you see on a CBC that can indicate Addison’s disease ?

A

Lack of a stress leukogram in a very sick patient (due to lack of cortisol)

73
Q

What chemistry changes are associated with hypoadrenocorticism ?

A

Pre-renal azotemia

Increased [BUN]

  • dehydration
  • gastrointestinal hemorrhage (melena)

Hypoglycemia

74
Q

What is the test of choice for hypoadrenocorticism ?

A

ACTH stimulation test

Primary hypoadrenocorticism has atrophied adrenals –> administration of ACTH will not cause a response

75
Q

What electrolyte abnormality will be present in an addisons patient?

A

Hyponatremia

Hyperkalemia

RUSVM Clinical Pathology (18 decks)

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