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425 - sys path > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

What do thyroid C (parafollicular) cells do?

A

secrete calcitonin in response to increased blood Ca (hypercalcemia)

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2
Q

What do thyroid follicular cells do?

A

Thyroglobulin –> monoiodotyrosine (MIT) and diiodotyrosine (DIT) –> biologically active hormones T3 and T4

under the influence of TSH and TRH

negative feedback on hypothalamus and adenohypophysis

regulate growth rate of metabolism and growth

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3
Q

what disorder of the C cells do we have to know?

A

C-cell (parafollicular cell) tumors

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4
Q

what disorders involving hypo function of the thyroid gland do we have to know?

A

hypothyroidism
congenital hypothyroidism (goitre, CHDS of foals)

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5
Q

what disorders involving hyper function of the thyroid gland do we have to know?

A

hyperthyroidism
nodular hyperplasia, follicular tumors

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6
Q

Hypothyroidism results in what pathophys thing?

A

decreased concentrations of thyroid hormones T3 and T4

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7
Q

what is one of the most common endocrinopathies of dogs? which breeds most affected?

A

hypothyroidism
beagles, daschunds

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8
Q

what are the causes of hypothyroidism

A

primary thyroid disease (idiopathic follicular collapse, lymphocytes thyroiditis)

rarely pituitary or hypothalamic lesion resulting in lowered TSH or TRH

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9
Q

what’s the lesion?

A

thyroid gland atrophy

thyroid atrophy makes the parathyroid glands more prominent (arrow)

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10
Q

what are the extra-thyroidal lesions of hypothyroidism?

A

reduction in BMR –> weight gain)
cutaneous
reproductive
hypercholesterolemia –> atherosclerosis

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11
Q

what are some examples of cutaneous lesions present in hypothyroidism?

A

bilaterally symmetrical alopecia
hyperkeratosis
hyperpigmentation
myxedema

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12
Q

what is goiter?

A

clinical term used to describe a non-neoplastic enlargement of the thyroid glands

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13
Q

what are some causes of goiter?

A

multiple cases, but have a shared pathogenesis
ex. iodine deficient diest, goitrogenic compounds, excess dietary iodine, genetic enzyme defects (Dyshormonogenetic goiter)

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14
Q

what is the pathogenesis of goiter, no matter the cause?

A
  1. inciting cause
  2. inadequate thyroid hormone synthesis
  3. decreased blood levels of T3 and T4
  4. increased TRH
  5. increased TSH
  6. hypertrophy/hyperplasia of follicular cells
  7. goiter
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15
Q

what’s the lesion?

A

goiter

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16
Q

thyroid gland. what’s the lesion?

A

goiter

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17
Q

what are the gross lesions of a thyroid gland with goiter?

A

bilaterally enlarged, dark purple thyroid glands

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18
Q

What does CHDS stand for?

A

Congenital Hypothyroidism-Dysmaturity Syndrome (in foals)

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19
Q

True or false: CHDS is common in western Canada

A

true

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20
Q

CHDS is characterized by ____ ____ and _____ _____.

A

Perinatal death, MSK malformations

21
Q

with CHDS, there’s _____ gestation but foals appear _____.

A

prolonged
dysmature

22
Q

what are the MSK abnormalities that come with CHDS?

A

contracted or ruptured tendons
mandibular prognathia
immature carpal and tarsal bones on radiographs

23
Q

This goat has this lesion, plus contracted tendons and immature carpal and tarsal bones. what might this foal have?

A

congenital hypothyroidism-dysmaturity syndrome

24
Q

with CHDS cases, why must you ALWAYS take the thyroid for histo?

A

grossly, the thyroid may look normal, but microscopic lesions are present

25
Q

true or false: the etiology of CHDS is unknown

A

true

26
Q

hyperthyroidism results in what pathophys thing?

A

elevated circulating levels of thyroid hormones (T3 or T4)

27
Q

dogs commonly get ____ and cats commonly get _____

A

hypothyroidism
hyperthyroidism

28
Q

true or false: hyperthyroidism is common in dogs

A

false! rare in dogs

29
Q

what is one of the most common endocrine diseases of cats?

A

hyperthyroidism

30
Q

what is the typical signalment for a cat with hyperthyroidism?

A

geriatric

31
Q

why is hyperthyroidism rare in dogs?

A

they have more efficient enterohepatic excretion of thyroid hormones

32
Q

if dogs get hyperthyroidism, how do they get it?

A

thyroid follicular tumors (Carcinoma > adenoma)

33
Q

Hyperthyroidism results in what 2 important things clinically?

A

increased BMR
cardiac manifestations

34
Q

hyperthyroidism causes increased BMR. what are the results of this?

A

weight loss despite ravenous appetite!!

PU/PD, nervous or hyper excitability, heat intolerance

35
Q

hyperthyroidism causes cardiac manifestations. What are two clinical signs of this? what gross lesion can you see?

A

tachycardia, dysrhythmias
concentric hypertrophy of the heart (DON’T MISTAKE THIS FOR PRIMARY HYPERTROPHIC CARDIOMYOPATHY!)

36
Q

Tell me which lesions are most common with hyperthyroidism

A

multifocal nodular hyperplasia and thyroid follicular adenomas > thyroid follicular carcinoma

37
Q

Hyperthyroidism:
Cats most commonly get what lesions?
Dogs most commonly get what lesions?

A

Cats: multifocal nodular hyperplasia, thyroid follicular cell adenoma

Dogs: thyroid follicular carcinoma

38
Q

What species/signalments do multifocal nodular hyperplasias occur in most commonly?

A

old horses, cats, dogs

39
Q

what do multifocal nodular hyperplasias that cause hyperthyroidism look like grossly?

A

multiple, tan to brown, nonencapsulated nodules

40
Q

this is from a cat with hyperthyroidism. what’s the lesion/cause?

A

multifocal nodular hyperplasia

41
Q

what species do thyroid follicular cell adenomas occur in most commonly ?

A

cats

42
Q

malignant thyroid tumors are more common in _____, benign thyroid tumors are more common in ____.

A

dogs, cats

43
Q

what do thyroid follicular cell adenomas that cause hyperthyroidism look like grossly?

A

single, white to tan, well-defined and encapsulated mass

44
Q

tell me the differences between multifocal nodular hyperplasia and thyroid follicular cell adenomas in terms of gross appearance?

A

Adenoma: single, encapsulated, white to tan
Hyperplasia: multiple, tan to brown, non encapsulated

45
Q

thyroid follicular carcinomas:
1) can develop where?
2) invasive/non-invasive?
3) metastasize ____(early/late) to where?

A

1) ectopic thyroid tissue
2) non-invasive
3) early, lungs

46
Q

what is the typical signalment of an animal with a thyroid c-cell tumor?

A

old bull

47
Q

what is the cause of thyroid c-cell tumors?

A

unknown, but might be linked to high calcium diets

48
Q

a bull with a thyroid c-cell tumor will have concurrent… what?

A

pheochromocytoma and pituitary tumors

49
Q

true or false: thyroid c-cell tumors are only adenomas

A

false! both adenomas and carcinomas

425 - sys path (38 decks)

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