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CS2 Exam I > 5: Thyroid Hormones - Wilson > Flashcards

5: Thyroid Hormones - Wilson Flashcards

1
Q

leading cause of preventable brain damage worldwide

A

iodine deficiency

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2
Q

large hemodimeric glycoprtn made in follicular cells and secreted through the apical membrane forming a major component of colloid

A

thyroglobulin

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3
Q

source of iodine

A

diet (comes in the form iodide)

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4
Q

low dietary iodine –>

A

goiter

enlargement of thyroid gland to better scavenge low levels of iodine
-persistnetly elevated TSH drives growth

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5
Q

incorporation of iodine into thyroglobulin =

A

organification of iodine

  • catalyzed by throid peroxidase on apical membrane
  • uses iodide ions to reduce H2O2 (produced by NADPH oxidase) to water
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6
Q

more T_ is formed than T_

A

more T4 is formed than T3

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7
Q

about ____ molecules of thyroid hormone are formed per thyroglobulin dimer

A

2-5

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8
Q

small amounts of iodinated thyroglobulin enter the serum via…

A

transcytosis

easy to measure in the clinical laboratory

levels will increase with graves disease and thyroiditis

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9
Q

______ of the hypothalamus release TRH

A

parvicellular neurons

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10
Q

thyrotropin =

A

TSH (different name for same thing)

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11
Q

__ and _____ inhibit TSH secretion

A

somatostatin and dopamine

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12
Q

__ binds to thryorid binding globin more tightly than ___ —?

A

T4 tighter than T3

contributes to longer half-life of T4 compared to T3

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13
Q

the biologically active form of T3/4 is the _____

A

free form - not the bound form (more T3 is free- T3 is more biologically active )

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14
Q

80% of circulating T3 is generated by…

A

deiodinase reactions of T4

major sites of deiodination are liver and kidney

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15
Q

major source of circulating T3

A

type I deiodinase

production of t3 in peripheral tissues

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16
Q

important in the control of thyroid hormone release

A

type II deiodinase

converts t4->t3

important in tissues that generate t3 locally from t4 rather than acquiring from the circulaiton

17
Q

considered to be major physiological terminator of thyroid hormone action in peripheral tissue

A

type III deiodinase

does not convert T4 to T3 (makes rT3 or T2)

high t3 will induce expression of type III deiodinase

18
Q

facilitates elimination in bile

A

glucoronidation of thyroid hormone in liver

19
Q

lack of thyroid hormone during development leads to …

A

mental retardation, growth, and developmental delay

20
Q

how does thyroid hormone increase basal metabolic rate?

A
  • increase transcription of Na/K ATPase

- stimulated transcription of mitochondrial uncoupling prtn –> release heat

21
Q

how does thyroid hormone regulate carbohydrate and lipid metabolism?

A
  • enhance carbohydrate absorption and oxidation
  • stimulate glycogen breakdown and gluconeogenesis
  • stimulate lipolysis
  • stimulate cholesterol synthesis/degradation
22
Q

hematopoietic effects of thyroid hormone

A
  • increased erythropoietin production

- increased 23bisphospholglycerate content of erythrocytes

23
Q

GI effects of thyroid hormone

A

increased gut motility

24
Q

graves disease =

A

autoimmune disease with antibodies binding to TSH receptor –> hyperthyroidism

25
Q

hashimoto’s thyroiditis =

A

autoimmune disease with antibodies to thyroid peroxidase, thyroglobulin, TSH receptor blocking antiboies –> decrease hormone production and secretion

26
Q

in the absence of bound thyroid hormone, thyroid hormone receptor/RXR complex…

A

recruits a histone deacetylase –> condensation of chromatin and inhibition of transcription

27
Q

binding of thyroid hormone triggers conformation change in thyroid hormone receptors …

A

HDAC released and HAT binds in its place –> leads to relaxation of chromatin and enhancement of transcription

28
Q

what thyroid hormones work with mitochondrial bioenergetics?

A

T2

29
Q

what mitochondrial hormones are responsible for alterations in actin cytoskeleton?

A

T4 and rT3

CS2 Exam I (18 decks)

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