Thyroid

Question 1

Function of thyroid gland

Answer 1

basal metabolic rate
lipid, protein, and carb metabolism

Question 2

Terms for decreased and increased secretion of thyroid hormone.

Answer 2

decreased: hypothyroidism
increased: hyperthyroidism

Question 3

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

Answer 3

isthmus

Question 4

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

Answer 4

True

Question 5

What two vessels supply blood to the thyroid gland?

Answer 5

cranial thyroid artery
caudal thyroid artery

Question 6

__________ cells line thyroid follicles and produce colloid.

Answer 6

follicular epithelial

Question 7

What 2 things does colloid of thyroid follicles contain?

Answer 7

1. thyroglobulin
2. thyroid peroxidase

Question 8

What is thyroglobulin? What does it contain?

Answer 8

glycoprotein
stores thyroid hormones + tyrosine

Question 9

What does thyroid peroxidase do?

Answer 9

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

Question 10

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

Answer 10

monoiodotyrosine OR diiodotyrosine

Question 11

What is the full name for T3? T4?

Answer 11

T3 = triiodothyronine
T4 = tetraiodothyronine (thyroxine)

Question 12

Monoiodotyrosine combines with diiodotyrosine to form _________ and ______.

Answer 12

T3 (triiodothyronine)
rT3 (reverse triiodothyronine)

Question 13

When two diiodotyrosine come together, it forms ________.

Answer 13

T4

Question 14

Parafollicular cells of the thyroid gland produce ________.

Answer 14

calcitonin

Question 15

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

Answer 15

increases
inhibits

Question 16

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

Answer 16

TSH (from pituitary)

Question 17

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

Answer 17

rough endoplasmic reticulum

Question 18

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

Answer 18

mannose (carbohydrate)
golgi complex

Question 19

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

Answer 19

galactose

Question 20

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.

Answer 20

convex
cis
concave
trans

Question 21

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

Answer 21

follicular epithelial cell

Question 22

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

Answer 22

exocytosis

Question 23

Circulating _______ is actively transported into the follicular epithelial cell.

Answer 23

iodide (I-)

Question 24

What transports circulating iodide into the follicular epithelial cell?

Answer 24

Na+/I- symporter

Question 25

Where is the Na+/I- symporter located?

Answer 25

basolateral membrane of follicular epithelial cell

Question 26

What stimulates the Na+/I- symporter?

Answer 26

TSH (thyroid stimulating hormone)

Question 27

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

Answer 27

TRH (thyrotropin releasing hormone) TSH (thyroptin)

Question 28

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

Answer 28

TRH (thyrotropin releasing hormone) TSH (thyrotropin)

Question 29

How is thyroid peroxidase synthesized?

Answer 29

by follicular epithelial cells enters follicular lumen same as thyroglobulin

Question 30

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

Answer 30

pendrin

Question 31

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

Answer 31

apical

Question 32

___ and ___ are biologically active while ___ is inactive.

Answer 32

T3 + T4 rT3

Question 33

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

Answer 33

TSH pinocytosis

Question 34

Pinocytotic vesicles fuse with _______ to form _______.

Answer 34

primary lysosomes --> secondary lysosomes

Question 35

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

Answer 35

proteases (cathepsins)

Question 36

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

Answer 36

capillaries

Question 37

What is meant by "free" T3 and T4?

Answer 37

not bound to plasma proteins

Question 38

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

Answer 38

False - both readily enter

Question 39

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

Answer 39

T4 T3

Question 40

What process occurs to convert T4 to T3?

Answer 40

deiodinated

Question 41

What process occurs to convert T4 to T3?

Answer 41

deiodinated (remove iodide)

Question 42

T3 binds to ______ receptors to alter ______.

Answer 42

nuclear (chromatin) transcription

Question 43

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

Answer 43

True

Question 44

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

Answer 44

inhibited (negative feedback) to both hypothalamus and pituitary

Question 45

Distinguish between primary, secondary, and tertiary hypothyroidism.

Answer 45

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)

Question 46

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

Answer 46

1. secondary 2. primary 3. tertiary

Question 47

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

Answer 47

cold warmth

Question 48

What are follicular epithelial cells derived from?

Answer 48

pharyngeal endoderm

Question 49

What are parafollicular cells derived from?

Answer 49

neural crest ectoderm

Question 50

Name the effect T3 and T4 have on each system: 1. metabolism 2. GI tract 3. heart

Answer 50

1. increase BMR 2. maintain smooth muscle function 3. increase B receptor synthesis

Question 51

T3 and T4 maintain ______ synthesis and _____ gland function.

Answer 51

protein sebaceous

Question 52

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

Answer 52

Hypo: constipation, bradycardia, dry/dull coat, cold intolerant, weight gain, lethargy Hyper: V+ & D+, tachycardia, patchy/oily coat, heat intolerant, weight loss, nervousness