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Endocrinology > Thyroid > Flashcards

Thyroid Flashcards

1
Q

Function of thyroid gland

A

basal metabolic rate
lipid, protein, and carb metabolism

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2
Q

Terms for decreased and increased secretion of thyroid hormone.

A

decreased: hypothyroidism
increased: hyperthyroidism

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3
Q

______ separates the lobes of the thyroid gland in the dog, cat, and horse.

A

isthmus

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4
Q

(T/F) The thyroid has a fibrous capsule than can be dissected from the organ.

A

True

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5
Q

What two vessels supply blood to the thyroid gland?

A

cranial thyroid artery
caudal thyroid artery

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6
Q

__________ cells line thyroid follicles and produce colloid.

A

follicular epithelial

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7
Q

What 2 things does colloid of thyroid follicles contain?

A
  1. thyroglobulin
  2. thyroid peroxidase
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8
Q

What is thyroglobulin? What does it contain?

A

glycoprotein
stores thyroid hormones + tyrosine

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9
Q

What does thyroid peroxidase do?

A

converts iodide –> intermediate form which binds to aromatic ring on tyrosine in thyroglobulin

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10
Q

What are the two possible intermediate forms produced when thyroid peroxidase converts iodide?

A

monoiodotyrosine OR diiodotyrosine

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11
Q

What is the full name for T3? T4?

A

T3 = triiodothyronine
T4 = tetraiodothyronine (thyroxine)

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12
Q

Monoiodotyrosine combines with diiodotyrosine to form _________ and ______.

A

T3 (triiodothyronine)
rT3 (reverse triiodothyronine)

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13
Q

When two diiodotyrosine come together, it forms ________.

A

T4

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14
Q

Parafollicular cells of the thyroid gland produce ________.

A

calcitonin

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15
Q

Calcitonin secretion increases as calcium (increases/decreases) which (stimulates/inhibits) osteoclasts.

A

increases
inhibits

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16
Q

All functions of the follicular epithelial cells of the thyroid gland dependent upon _______.

A

TSH (from pituitary)

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17
Q

Where is the protien portion of thyroglobulin synthesized in the follicular epithelial cell?

A

rough endoplasmic reticulum

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18
Q

_____ is added to the protein portion of thyroglobulin in the rough ER before it is transferred to _______.

A

mannose (carbohydrate)
golgi complex

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19
Q

An additional carbohydrate, _______, is added to thyroglobulin once in the golgi complex.

A

galactose

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20
Q

When entering the golgi complex, vesicles fuse with the (convex/concave) or (trans/cis) face of the golgi. When exiting, they bud from the (convex/concave) or (trans/cis) face.

A

convex
cis
concave
trans

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21
Q

Once secretory granules with thyroglobulin bud from the golgi, they fuse with apical membrane of __________.

A

follicular epithelial cell

22
Q

Thyroglobulin is released into the lumen of the thyroid follicle via what process?

A

exocytosis

23
Q

Circulating _______ is actively transported into the follicular epithelial cell.

A

iodide (I-)

24
Q

What transports circulating iodide into the follicular epithelial cell?

A

Na+/I- symporter

25
Q

Where is the Na+/I- symporter located?

A

basolateral membrane of follicular epithelial cell

26
Q

What stimulates the Na+/I- symporter?

A

TSH (thyroid stimulating hormone)

27
Q

_____ stimulates _____ which stimulates Na+/I- symporter to transport iodide into the follicular epithelial cell in the thyroid gland.

A

TRH (thyrotropin releasing hormone)
TSH (thyroptin)

28
Q

_____ stimulates _____ which stimulates Na+/I- symporter to transport iodide into the follicular epithelial cell in the thyroid gland.

A

TRH (thyrotropin releasing hormone)
TSH (thyrotropin)

29
Q

How is thyroid peroxidase synthesized?

A

by follicular epithelial cells
enters follicular lumen same as thyroglobulin

30
Q

Iodide is transported to the follicular lumen by a transmembrane protein called ________.

A

pendrin

31
Q

Pendrin is a transmembrane protein on the (apical/basolateral) membrane of follicular epithelial cells.

A

apical

32
Q

___ and ___ are biologically active while ___ is inactive.

A

T3 + T4
rT3

33
Q

____ stimulates follicular epithelial cells to ingest colloid by what process?

A

TSH
pinocytosis

34
Q

Pinocytotic vesicles fuse with _______ to form _______.

A

primary lysosomes –> secondary lysosomes

35
Q

What enzyme in secondary lysosomes digest thyroglobulin and liberate T3 & T4?

A

proteases (cathepsins)

36
Q

From the follicular epithelial cell, T3 and T4 diffuse into _______ surrounding the follicle once liberated from colloid.

A

capillaries

37
Q

What is meant by “free” T3 and T4?

A

not bound to plasma proteins

38
Q

(T/F) Free T4 readily enters cells while T3 does not.

A

False - both readily enter

39
Q

In the target cell, ___ is converted to ___, the active form.

A

T4
T3

40
Q

What process occurs to convert T4 to T3?

A

deiodinated

41
Q

What process occurs to convert T4 to T3?

A

deiodinated (remove iodide)

42
Q

T3 binds to ______ receptors to alter ______.

A

nuclear (chromatin)
transcription

43
Q

(T/F) TSH stimulates both the synthesis and release of T3 and T4.

A

True

44
Q

As blood levels of T3 and T4 rise, what occurs with TSH and TRH?

A

inhibited (negative feedback) to both hypothalamus and pituitary

45
Q

Distinguish between primary, secondary, and tertiary hypothyroidism.

A

Primary: problem with thyroid gland (no thyroid hormone production)

Secondary: problem with pituitary (no TSH to stimulate T3/T4 production)

Tertiary: problem with hypothalamus (no TRH –> down TSH –> down T3/T4)

46
Q

Which type of hypothyroidism is uncommon in dogs? Which is common? Which is not reported in animals?

A
  1. secondary
  2. primary
  3. tertiary
47
Q

(Cold/warmth) stimulate secretion of TRH, and therefore TSH, resulting in increased T3 and T4 release. (Cold/warmth) does the opposite.

A

cold
warmth

48
Q

What are follicular epithelial cells derived from?

A

pharyngeal endoderm

49
Q

What are parafollicular cells derived from?

A

neural crest ectoderm

50
Q

Name the effect T3 and T4 have on each system:

  1. metabolism
  2. GI tract
  3. heart
A
  1. increase BMR
  2. maintain smooth muscle function
  3. increase B receptor synthesis
51
Q

T3 and T4 maintain ______ synthesis and _____ gland function.

A

protein
sebaceous

52
Q

Match each extreme to the diseased state of either hypo or hyperthyroidism:

  1. V+ & D+ | constipation
  2. tachycardia | bradycardia
  3. dry/dull coat | patchy/oily coat
  4. heat intolerant | cold intolerant
  5. weight loss | weight gain
  6. lethargy | nervousness
A

Hypo: constipation, bradycardia, dry/dull coat, cold intolerant, weight gain, lethargy

Hyper: V+ & D+, tachycardia, patchy/oily coat, heat intolerant, weight loss, nervousness

Endocrinology (10 decks)

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