Thyroid Pt 1

Question 1

the thyroid gland is innervated why what nerves?

Answer 1

sympathetic

Question 2

what are the functional units of the thyroid gland?

Answer 2

thyroid follicles

Question 3

describe the structure of thyroid follicles

Answer 3

single layer of epithelial cells surrounding a lumen that contains colloid

Question 4

what kinds of follicles are in the thyroid gland?

Answer 4

thyroid follicles, parafollicular cells

Question 5

parafollicular cells are a source of…

Answer 5

calcitonin

Question 6

what is the function of the thyroid gland?

Answer 6

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

Question 7

what regulates the release of thyroid hormones? how?

Answer 7

blood flow; affects delivery of TSH, iodine and nutrients

Question 8

what controls the blood flow through the thyroid gland?

Answer 8

postganglionic sympathetic nerves

Question 9

what are the biologically active forms of thyroid hormone?

Answer 9

T4 and T3

Question 10

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

Answer 10

rT3 and T2; formed in peripheral tissues

Question 11

where is TSH made?

Answer 11

anterior pituitary

Question 12

which benzene ring is numbered with a prime?

Answer 12

distal benzene ring

Question 13

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

Answer 13

transporter: NIS
thyroglobuline: TG
thyroid peroxidase: TPO

Question 14

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

Answer 14

iodized salt

Question 15

what does NIS do?

Answer 15

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

Question 16

significance of perchlorate?

Answer 16

blocker of iodine; can be used to treat hyperthyroidism

Question 17

describe the significance of radioactive iodine

Answer 17

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

- can be used to treat cancer

Question 18

describe relationship of other halogens with iodine

Answer 18

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

Question 19

when is thyroshield recommended?

Answer 19

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

Question 20

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

Answer 20

false

Question 21

which enzyme is responsible for the iodination of Tg?

Answer 21

TPO - thyroperoxidase

Question 22

which enzyme makes H2O2 necessary for the organification of TG?

Answer 22

dual-oxidase

Question 23

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

Answer 23

regulation of TPO

Question 24

numbering of t3?

Answer 24

3, 5, 3’

Question 25

what is sick euthyroid syndrome?

Answer 25

when there's more r-T3 (inactive) than T3 (active) similar to hypothyroidism

Question 26

most r-T3 is produced where?

Answer 26

peripheral tissues (product of metabolism in general)

Question 27

true or false: T3 and T4 require a binding protein

Answer 27

true, they are lipophilic

Question 28

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

Answer 28

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

Question 29

what are the binding proteins of T3 and T4 called?

Answer 29

- thyroxine binding globulin (TBG) - Transthyretin, aka thyroxine binding prealbumin TBPA - Albumin

Question 30

do thyroid epithelial cells produce more of T3 or T4?

Answer 30

T4 - more concentrated but less active

Question 31

which is more biologically active? T3 or T4?

Answer 31

T3

Question 32

why is T4 more concentrated than T3?

Answer 32

it's better at binding to binding proteins

Question 33

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

Answer 33

false: only free ones are active

Question 34

in what scenarios would more binding proteins be produced?

Answer 34

pregnancy, use of oral contraceptives

Question 35

in what scenarios would fewer binding proteins be produced?

Answer 35

starvation, liver disease

Question 36

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

Answer 36

more

Question 37

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

Answer 37

Tg: thyroid's follicular cells | binding proteins: liver

Question 38

which deiodinase converts T4 to rT3?

Answer 38

type III

Question 39

what's unique about deiodinases?

Answer 39

they contain the 21st amino acid (selenocysteine)

Question 40

what regulates local modulation of thyroid hormone?

Answer 40

deiodinases

Question 41

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

Answer 41

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