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ANSC 424 > Thyroid Pt 1 > Flashcards

Thyroid Pt 1 Flashcards

1
Q

the thyroid gland is innervated why what nerves?

A

sympathetic

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2
Q

what are the functional units of the thyroid gland?

A

thyroid follicles

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3
Q

describe the structure of thyroid follicles

A

single layer of epithelial cells surrounding a lumen that contains colloid

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4
Q

what kinds of follicles are in the thyroid gland?

A

thyroid follicles, parafollicular cells

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5
Q

parafollicular cells are a source of…

A

calcitonin

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6
Q

what is the function of the thyroid gland?

A

secrete the quantity of thyroid hormone to meet the demand of peripheral tissues

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7
Q

what regulates the release of thyroid hormones? how?

A

blood flow; affects delivery of TSH, iodine and nutrients

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8
Q

what controls the blood flow through the thyroid gland?

A

postganglionic sympathetic nerves

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9
Q

what are the biologically active forms of thyroid hormone?

A

T4 and T3

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10
Q

what are the inactive form of thyroid hormone? where does it get made?

A

rT3 and T2; formed in peripheral tissues

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11
Q

where is TSH made?

A

anterior pituitary

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12
Q

which benzene ring is numbered with a prime?

A

distal benzene ring

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13
Q

what proteins are necessary for the synthesis of T4 and T3?

A

transporter: NIS
thyroglobuline: TG
thyroid peroxidase: TPO

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14
Q

where does most of our iodine intake occur in North America?

A

iodized salt

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15
Q

what does NIS do?

A

brings in iodine against its concentration gradient while also bringing in Na. This is possible due to maintenance of the Na gradient by Na/KATPase

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16
Q

significance of perchlorate?

A

blocker of iodine; can be used to treat hyperthyroidism

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17
Q

describe the significance of radioactive iodine

A
  • bad/poses danger if you’re exposed to radiation

- can be used to treat cancer

18
Q

describe relationship of other halogens with iodine

A

anions can compete with iodine with transport (just trying to balance charge); so when their concentration is high, this can inhibit iodine uptake and lead to hypothyroidism

19
Q

when is thyroshield recommended?

A

when there’s a radioactive accident; it brings in a lot of iodine that the thyroid gland can use as competition with the radioactive isotope

20
Q

true or false: the thyroid gland will show preference to uptaking the iodine it needs over an isotope

A

false

21
Q

which enzyme is responsible for the iodination of Tg?

A

TPO - thyroperoxidase

22
Q

which enzyme makes H2O2 necessary for the organification of TG?

A

dual-oxidase

23
Q

what aspect of the thyroid gland is often targeted in drug treatment?

A

regulation of TPO

24
Q

numbering of t3?

A

3, 5, 3’

25
Q

what is sick euthyroid syndrome?

A

when there’s more r-T3 (inactive) than T3 (active)

similar to hypothyroidism

26
Q

most r-T3 is produced where?

A

peripheral tissues (product of metabolism in general)

27
Q

true or false: T3 and T4 require a binding protein

A

true, they are lipophilic

28
Q

what would be the side effect of a drug that competes for the binding proteins of T3 and T4? (e.g. anti-epileptic drugs)

A

effect similar to hyperthyroidism because there would be more free T3 and T4

29
Q

what are the binding proteins of T3 and T4 called?

A
  • thyroxine binding globulin (TBG)
  • Transthyretin, aka thyroxine binding prealbumin TBPA
  • Albumin
30
Q

do thyroid epithelial cells produce more of T3 or T4?

A

T4 - more concentrated but less active

31
Q

which is more biologically active? T3 or T4?

A

T3

32
Q

why is T4 more concentrated than T3?

A

it’s better at binding to binding proteins

33
Q

true or false: only bound T3 and T4 are biologically active

A

false: only free ones are active

34
Q

in what scenarios would more binding proteins be produced?

A

pregnancy, use of oral contraceptives

35
Q

in what scenarios would fewer binding proteins be produced?

A

starvation, liver disease

36
Q

the more binding protein, the (more/less) total hormone required to maintain free hormone level

A

more

37
Q

Tg is produced where? Thyroxine binding globulin is produced where?

A

Tg: thyroid’s follicular cells

binding proteins: liver

38
Q

which deiodinase converts T4 to rT3?

A

type III

39
Q

what’s unique about deiodinases?

A

they contain the 21st amino acid (selenocysteine)

40
Q

what regulates local modulation of thyroid hormone?

A

deiodinases

41
Q

what would it mean for cells if they down-regulated their production of deiodinases?

A

in the event that there’s less free and active T3 and T4, they can reduce the amount of deiodinases to better use what’s available

ANSC 424 (12 decks)

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