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Physiology II > Endocrine: Thyroid > Flashcards

Endocrine: Thyroid Flashcards

1
Q

Parafollicular cells release…

A

calcitonin

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2
Q

what is the functional unit of the thyroid?

A

follicular cell

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3
Q

hyperthyroid results in ______ reabsorption, and

A

colloid reabsorption, narrowed lumen

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4
Q

hypothyroid results in _____ cells

A

widened lumen

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5
Q

4 major steps of thyroid hormone synthesis?

A

iodide uptake, incorporation of iodide to tyr, coupling, diffusion

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6
Q

TSH binding on the basolateral membrane of follicular cells has what effect?

A

stimulates all steps of thyroid hormone synth

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7
Q

What inhibits TSH and TRH release?

A

T3/T4 increase

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8
Q

What 4 biologic effects occur when TSH binds to basolateral receptor?

A

increased NIS, Tg, TPO, T3/T4

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9
Q

What is responsible for peripheral conversion of T4 to T3?

A

peripheral deiodinases

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10
Q

What is the daily intake of iodide?

A

400 ug

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11
Q

total iodide content of the thyroid is…

A

7500 ug

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12
Q

What is the ratio of iodide in hormone to the amount of daily turnover? What effect does this have?

A

100:1, protects from deficiency for 2 months

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13
Q

What percent of iodide is released as HI/Free?

A

1% (70-80 ug)

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14
Q

What provides energy for the 2:1 na:iodide co-transport of the NIS?

A

Sodium gradient from sodium potassium pump

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15
Q

Once in the cell, _____ allows some iodide efflux to colloid

A

anoctamin-1 (anion channel)

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16
Q

low iodide has what effect on NIS activity?

A

increased

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17
Q

What effects does diet-induced iodide deficiency have on TSH release?

A

lack of T3/T4 production, no negative feedback, increased TSH secretion, increased NIS activity

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18
Q

Mutated NIS in ITD has what effect?

A

reduced T3/T4

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19
Q

what provides iodide for thyroid hormone synthesis in infants?

A

NIS in mammary gland

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20
Q

Is NIS activity in lactating glands under TSH regulation?

A

no

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21
Q

In Graves disease, anti-bodies are directed against…

A

TSH receptor, NIS

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22
Q

In grave’s disease, what causes growth of the thyroid?

A

thyroid stimulating immunoglobulins

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23
Q

Graves disease results in hyper/hypothyroidism, having what effect on TSH?

A

Hyperthyroidism, decreased TSH

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24
Q

What substances inhibits NIS?

A

perchlorate and thiocyanate

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25
___ reflects activity of the thyroid gland, and can be measured via iodine 123 tracer...
NIS
26
when iodine cannot be incorporated into tyrosine, it is called....
organification defect
27
What carries iodide inside the follicular cell across the apical membrane
pendrine
28
This disease: - goiter in childhood - hearing loss - hypothyroidism - gene mutation
pendred syndrome
29
What oxidizes iodide to iodine for Tyr binding?
TPO using H2O2
30
Iodide is bound to tyr residues on ____ by which enzyme? (organification)
binds tyr on Thyroglobulin via TPO
31
Coupling occurs when iodinated tyrosines on Tg take on tertiary and quaternary form. Couling yields what two products?
monoiodinated tyrosine (MIT) diiodinated tyrosine (DIT)
32
20% of tyr residues on Tg will be iodinated. What percent will be coupled to become active thyroid hormones?
5%
33
Iodide organification can occur independent of TSH in high plasma iodide conentrations. Iodide itself can inhibit organification in order to prevent excess thyroid hormone production. What is this called?
wolff-chaikoff effect
34
how long does wolf-chaikoff inhibition last?
few days, reduced iodine
35
Two DIT =
T4
36
MIT + DIT =
T3
37
Where does the Tg molecule with T3/T4 get stored in the cell? Until when?
stored in colloid until TSH stimulation
38
Follicular cell engulfs the T3/T4 containing Tg via...
megalin
39
in the follicular cell, what frees T3 and T4 from MIT and DIT?
intrathyroidal deiodinase
40
Hyperthyroidism is associated with an increase in what serum value?
high Tg levels in plasma due to leakage
41
What inhibits coupling and oxidation of iodide?
propylthiouricil (Graves Tx)
42
What 4 proteins do thyroid hormones bind to in the blood?
TBG, albumin, transthyretin, lipoprotein
43
What percent of each thyroid hormone is secreted from thyroid?
90% T4 | 10 % T3
44
what percent of T3 and T4 are bound in the blood?
99+%
45
What type of deiodinases activate T4 to T3 via outer ring deiodination?
Type 1 & Type 2 deiodinases
46
Which deiodinase inactivates T4 via inner ring deiodination?
Deiodinase Type 3
47
What 4 types of transporters bring thyroid hormones into the cell?
NTCP OATP LAT MCT
48
Which transporter has preference for T4?
OATP
49
Which transporter has preference for T3?
MCT
50
Mutations in which receptor are assoc. with physchomotor retardation and thyroid hormone resistance?
MCT
51
Are thyroid hormone carriers present at the BBB?
yes
52
Thyroid hormones bind to nuclear DNA where?
TRE promoter region
53
non-genomic effects of thyroid hormones increase stimulation of what channels?
(Calcium, sodium, potassium channels) Ca ATPase, L-type calcium sodium potassium pump, sodium and potassium channels NHE
54
What two calorigenic actions occur after T3/T4 stimulation?
increased BMR, body temp via sodium potassium pump
55
Where do calorigenic actions not occur?
brain, gonads, spleen
56
In the SNS, thyroid hormones increase synthesis of ______ via heterologues up-regulation
b-adrenergic (heart, skeletal, adipose)
57
What effect does thyroid hormone stimulation have on the heart?
increased CO, chronotropic, inotropic, decreased resistance (vasodilation, temp. reg effect)
58
What effects do thyroid hormones have on metabolism?
increased glucose absorption, gluconeogenesis, lipolysis, protein synth increased proteolysis
59
Tx for Graves...
surgery, radiation, beta blockers, PTU
60
Hypo or hyper thyroid? ``` weight gain cold intolerance sleepiness depression slow pulse HTN ```
hypo
61
Hypo or hyper thyroid? ``` increased appetite weight loss heat intolerance nervousness anxiety tremor Increased SBP Muscle weakness ```
hyper

Physiology II (28 decks)

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