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Endocrine Pathophys > Thyroid > Flashcards

Thyroid Flashcards

1
Q

T3/T4 are synthesized by what?

A

Thyroid follicle (central lumen specifically)

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2
Q

What is the thyroid follicle?

A

Thyrocytes (follicular cells) with central lumen

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3
Q

Calcitonin is synthesized by what?

A

Parafollicular cells

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4
Q

T3/T4 consist of?

A

Thyroglobulin and iodide

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5
Q

What is “iodide trapping”?

A

Thyroid stimulating hormone promotes intake of iodide into follicular cells

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6
Q

Where is thyroglobulin produced?

A

Follicular cell

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7
Q

What does thyroid stimulating hormone also stimulate?

A

Reuptake of T3/T4 back into cell to be released from thyroid gland

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8
Q

What percent of T3/T4 binds to thyroxine binding globulin

A

70%

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9
Q

What percent of T3/T4 binds to other protein carriers?

A

29%

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10
Q

What percentage of circulating T3/T4 is free T3?

A

0.3%

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11
Q

What percentage of circulating T3/T4 is free T4?

A

0.03%

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12
Q

What is “circulating storage” of T3/T4?

A

T3/T4 that is bound to carrier proteins
(inactive)

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13
Q

What happens when there is too much free T3/T4?

A

Hypothalamus releases less TRH and the anterior pituitary gland releases less TSH

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14
Q

What happens when there is too little free T3/T4?

A

Hypothalamus releases more TRH and the anterior pituitary gland releases more TSH

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15
Q

Which thyroid hormone is directly used by body tissue?

A

T3

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16
Q

How is T4 used by body tissue?

A

Metabolised in to T3 first

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17
Q

What enzyme converts T4 into T3 in cells?

A

D2

18
Q

What does D2 monitor?

A

That there is enough free T3 readily available in the cell

19
Q

What enzyme converts T4 into T3 in the liver/kidneys?

A

D1

20
Q

What does D1 monitor?

A

That there is enough available free T3 in the plasma

21
Q

What enzyme deactivates T3/T4?

A

D3

22
Q

When T4 is deactivated what is it converted into?

A

rT3

23
Q

When T3 is deactivated what is it converted into?

A

T2

24
Q

What does D3 monitor?

A

That there isn’t too much T3/T4 in the plasma

25
Q

How do thyroid hormones affect metabolism?

A

Stimulate energy consumption and metabolism which increases body temperature

26
Q

Thyroid hormones are ___________ with the sympathetic nervous system

A

synergistic

27
Q

How do thyroid hormones affect growth and development?

A

Critical for CNS and skeletal development
Works w/ growth hormone and reproductive hormones

28
Q

Insufficient thyroid hormones in newborns can cause?

A

Irreversible skeletal and neurological impairment

29
Q

What are the target tissues of thyroid hormones?

A

Heart, liver, pancreas, CNS, bones, adipose, GI tract

30
Q

How do thyroid hormones affect the heart?

A

Increases HR and cardiac output
T3 increases sensitivity to sympathetic system (epinephrine)

31
Q

How do thyroid hormones affect the pulmonary system?

A

Stimulate the brainstem to increase ventilation

32
Q

How do thyroid hormones affect adipose tissue?

A

Stimulate lipolysis

33
Q

How do thyroid hormones affect the liver?

A

Stimulate glycogenolysis, gluconeogenesis, ketogenesis, synthesis of VLDL

34
Q

How do thyroid hormones affect the pancreas?

A

Directly stimulate alpha and beta cells to produce glucagon and insulin

35
Q

How do thyroid hormones affect the CNS?

A

Increase CNS neuron sensitivity/excitability
Stimulate neuron growth and development

36
Q

What is the “critical window” for newborns in. regards to diagnosing thyroid hormone insufficiency?

A

2 weeks
Sooner the DX/TX the better the outcome

37
Q

How do thyroid hormones affect the bones?

A

Promotes bone growth
Stimulates osteoblast and osteoclast activity (homeostasis)

38
Q

Hypothyroidism is linked with increased risk of?

A

Osteoporosis

39
Q

How do thyroid hormones affect the GI tract?

A

Increases GI secretions and motility which promotes glucose absorption

40
Q

What is the Wolff-Chaikoff Effect?

A

High plasma iodide levels will decrease secretion of T3/T4

Endocrine Pathophys (12 decks)

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