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2 Endocrine > Physiology of the Thyroid Gland > Flashcards

Physiology of the Thyroid Gland Flashcards

1
Q

which endocrine grand secretes TRH?

A

hypothalamus

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2
Q

where does TRH go after it is secreted?

A

to the pituitary gland

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3
Q

what is TSH secreted by?

A

pituitary gland

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4
Q

what thyroid hormone does the thyroid primarily secrete?

A

T4

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5
Q

what does elevated T3/T4 in the blood plasma cause?

A

TSH to be inhibited

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6
Q

how is T3 made?

A

T4 is converted into it by deiodination

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7
Q

name all the thyroid hormones secreted by the thyroid gland?

A

T4
T3
calcitonin

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8
Q

what do the parathyroid glands produce?

A

parathyroid hormone

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9
Q

what vertebral levels is the thyroid gland located at?

A

C5-T1

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10
Q

what weight is the thyroid gland?

A

25-30g

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11
Q

when does the thyroid gland increase in size physiologically?

A

pregnancy

menstruation

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12
Q

parasympathetic innervation of the thyroid gland?

A

vagus nerve

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13
Q

sympathetic innervation of the thyroid gland?

A

superior, middle and inferior ganglia of the sympathetic trunk

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14
Q

arterial blood supply to the thyroid gland?

A

superior and inferior thyroid arteries

thyroid ima artery (embryological)

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15
Q

venous blood supply to the thyroid gland?

A

superior, middle and inferior thyroid vein

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16
Q

what vein(s) from the thyroid gland drain into the internal jugular vein?

A

superior and middle

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17
Q

what vein(s) from the thyroid gland drain into the brachiocephalic vein?

A

inferior

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18
Q

what is the berry ligament?

A

suspensory ligament located posteromedially to the thyroid gland

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19
Q

what should the thyroid look like on a technetium thyroid scan?

A

symmetrical darker areas over the lobes of the thyroid

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20
Q

what does the thyroid look like on a technetium thyroid scan of someone with graves disease?

A

darker, enlarged symmetrical lobes of the thyroid

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21
Q

what does the thyroid look like in hyperthyroidism?

A

1 lobe looks darker than the other

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22
Q

what cells in the thyroid make T3 and 4

A

follicular cells

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23
Q

where is colloid located?

A

in follicles of the thyroid

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24
Q

what is colloid?

A

tyrosine containing thyroglobulin filled with spheres enclosed by follicular cells

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25
what cells secrete calcitonin?
parafollicular C cells
26
important role of calcitonin in cancer?
is a tumour marker for MEDULLARY thyroid cancer
27
how can free T3 and 4 produced by the colloid get back into the bloodstream?
colloid undergoes pinocytosis some hormones go back into follicular cells hormones are released into bloodstream
28
what do follicular cells do?
make T3 and 4 control uptake of iodine into thyroid regulates hormones moving in/out of bloodstream
29
what does the colloid do?
contains a reservoir of thyroid hormone
30
how is T3 made?
iodine taken up by follicular cells, iodine attaches to tyrosine residues on thyroglobulin to make monoiodotyrosine and di-iodotyrosine units, 1 MIT + 1 DIT = T3
31
how is T4 made?
iodine taken up by follicular cells, iodine attaches to tyrosine residues on thyroglobulin to make monoiodotyrosine and di-iodotyrosine units, 1 MIT + 3DIT = T4
32
how do carbimazole and propylthiouracil stop new T3/4 production?
stop iodine attaching to tyrosine residues i.e preventing deiodination
33
what is the major biologically active thyroid hormone?
T3
34
how many times more potent is T3 than T4?
4 times
35
is most TH found free or bound?
bound to plasma proteins
36
what happens to the thyroid hormones in the colloid when TSH is in the bloodstream?
they are released via pinocytosis
37
what does T3 act on?
the nucleus of follicular cells via gene transcription
38
is T3/4 in blood the same as free T3/4?
no, free T3/4 is in colloid
39
is bound or unbound thyroid hormone the biologically active form?
unbound
40
what are the 3 plasma proteins that t3/4 bind to?
tbg ttr albumin
41
why do t3/4 bind to plasma proteins?
they are hydrophobic
42
is unbound or bound hormone available to the tissues?
unbound
43
if TBG were to increase, what effect would it have on free and bound T3/4?
wouldnt affect free | would increase bound
44
what liver and bile duct diseases increases tbg?
biliary cirrhosis hep A chronic hepatitis
45
what kidney disease decreases tbg?
nephrotic syndrome
46
does pregnancy increase or decrease tbg?
increase
47
how do thyroid hormones increase basal metabolic rate?
increase no and size of mitochondria increase oxygen use increase synthesis of resp chain enzymes
48
what effect do thyroid hormones have on blood glucose?
stimulate glycogenolysis and gluconeogenesis
49
what effect do thyroid hormones have on lipids?
increase fatty acid oxidation
50
what thyroid disease presents with slow intellectual function?
hypothyroidism
51
what thyroid disease presents with nervousness and hyperkinesis?
hyperthyroidism
52
what should TSH and thyroid hormone levels look like in normal people?
should stay the same throughout life
53
why are beta blockers good for treating hyperthyroidism?
slow down tachycardia and chronotropic rate
54
what effect do thyroid hormones have on TSH and TRH once they are in the blood stream?
switch off their production
55
what kind of receptor is the TSH receptor?
GPCR
56
what cell is the TSH receptor located on?
follicular cell
57
if a patient had decreased t3/4 and decreased tsh what would you suspect?
stress | secondary hypothyroidism
58
what effect does stress have on thyroid hormones?
inhibits TRH and TSH release
59
how many kinds of deiodinase enzyme are there?
3 (D1, 2 and 3)
60
what do the deiodinase enzymes do?
activate/deactivate thyroid hormones
61
which type of deiodinase enzyme is foiund in perpheral tissues?
D2
62
what type of deiodinase enzyme is found in pregnancy?
D3
63
where is D1 deiodinase enzyme found?
liver | kidney
64
what does D2 do?
converts T4 to T3 in tissues
65
if T3 is low, what could be going on?
not enough D2
66
what is cretinism and who gets it?
short stature and limiting mental function in children with thyroid hormone deficiency
67
main regulator of thyroid hormone?
TSH

2 Endocrine (35 decks)

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