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OLD "MBS 603" > Lecture & Vodcast 2 -- Exam 5 > Flashcards

Lecture & Vodcast 2 -- Exam 5 Flashcards

1
Q

What occurs in the follicle of the thyroid gland?

A

thyroid hormone (TH) production

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2
Q

What is so special about the way thyroid hormone is synthesized?

A

only hormone synthesized extracellularly

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3
Q

What is colloid in the thyroid gland?

A

thick liquid where thyroid hormone is made

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4
Q

What is the precursor molecule for thyroid hormone?

A

tyrosine

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5
Q

When synthesizing thyroid hormone, tyrosine is converted into ____ and _____

A

MIT
DIT

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6
Q

What is the difference between the intermediate of thyroid hormones MIT and DIT?

A

MIT: C3 iodide
DIT: C3 & C5 iodide

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7
Q

The combination of DIT + DIT results in the formation of ….

A

T4 (inactive)

  • most common in blood
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8
Q

The combination of MIT + DIT results in the formation of ….

A

T3 (active form)

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9
Q

What enzyme converts T4 into the active T3?

A

5’ deiodinase (removes 5’ iodine)

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10
Q

What enzyme converts T4 into the reverse T3?

A

type III deiodinase

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11
Q

What are the 7 steps of thyroid hormone synthesis?

A
  1. iodide trapping
  2. thyroglobulin synthesis
  3. iodination
  4. coupling
  5. endocytosis
  6. proteolysis
  7. secretion/recycling
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12
Q

What occurs during step 1 of thyroid hormone synthesis, iodide trapping?

A

Na/I symporter brings Na and iodide into cell

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13
Q

What occurs during step 2 of thyroid hormone synthesis, thyroglobulin synthesis?

A

thyroglobulin is made which is the source of tyrosine for later steps

** inside cell

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14
Q

What occurs during step 3 of thyroid hormone synthesis, iodination?

A

iodide is converted into iodine which combines with tyrosine

** apical side of cell

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15
Q

What occurs during step 4 of thyroid hormone synthesis, coupling?

A

MIT + DIT = T3
DIT + DIT = T4

** apical side of cell

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16
Q

What occurs during step 5 of thyroid hormone synthesis, endocytosis?

A

T4 / T3 is brought back inside cell to be recycled or stored to be secreted

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17
Q

What is the hypothalamic pituitary thyroid axis?

A

hypothalamus: TRH
pituitary: thyrotrophs sense TRH and release TSH
thyroid: TSH induces production and release of T4 and T3

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18
Q

Does somatostatin and dopamine __increase/decrease___ the release of TSH?

A

decrease

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19
Q

If you have just eaten what is the affect on TSH secretion?

A

increase (wants to increase metabolism)

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20
Q

If you are stuck in the snow for 12 hours what is the affect on TSH secretion?

A

decrease (wants to slow metabolism and preserve energy)

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21
Q

___ can directly AND indirectly negatively feedback to prevent TRH and TSH secretion

A

T4

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22
Q

What is the thyroid hormones primary role?

A

increase metabolism (increases after eating)

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23
Q

In primary hyperthyroidism, what is the affect on levels of T4, T3, and TSH

A

T3 & T4: increase
TSH: decrease

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24
Q

What is Graves disease?

A

autoantibodies that activate TSH receptor on thyroid causing increased T4 and T3 secretion

** hyperthyroidism

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25
Q

Does hyperthyroidism cause increased or decreased weight?

A

decreased (increased metabolism)

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26
Q

Why does hyperthyroidism cause a goiter?

A

thyroid gland swells due to constant stimulation of TSH by auto-Ab causing increased thyroid follicles size

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27
Q

In primary hypothyroidism, what is the affect on levels of T4, T3, and TSH?

A

T3 & T4: decrease
TSH: increase

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28
Q

Why does TSH levels increase in hypothyroidism?

A

no negative feedback due to lack of T3 and T4 so pituitary keeps making TSH

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29
Q

What is Hashimoto’s disease?

A

autoantibodies destroy thyroid follicles

  • hypothyroidism
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30
Q

Does hypothyroidism cause increased or decreased weight?

A

increase (decreased metabolism due to underactive thyroid)

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31
Q

Why does hypothyroidism cause decreased heart rate (bradycardia)?

A

decreased sympathetic activity

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32
Q

Why do babies with hypothyroidism have decreased growth and cognitive issues?

A

thyroid hormone is important in growth and brain development

33
Q

Hypercalcemia causes _________ nerve excitability

A

decreased

34
Q

Hypocalcemia causes _________ nerve excitability

A

increased

35
Q

Does hypo or hyper-calcemia cause tetany (spasms)?

A

hypocalcemia (increased nerve excitability)

36
Q

What 3 places regulate Ca2+ balance?

A

gut, bones, kidneys

37
Q

Osteoblasts or osteoclasts contain receptors for PTH, Vitamin D3 and estrogen.

A

osteoblasts (build bone)

38
Q

Osteoblasts or osteoclasts contain receptors for calcitonin.

A

osteoclasts (breaks down bone)

39
Q

What cells break down bone?

A

osteoclasts

40
Q

What cells build bone?

A

osteoblasts

41
Q

What are the 2 sources of vitamin D?

A

milk and sun

42
Q

What is the role of Vitamin D in regards to calcium?

A
  • regulates Ca2+ levels

stimulates formation of calbindin to remove Ca2+ out of cell

43
Q

Vitamin D3 is converted into ___________ in the liver which is a intermediate for active vitamin D

A

25-OH-vitaminD3

44
Q

What are the 2 forms of vitamin D made from 25-OH-vitamin D3?

A

1,25-OH- vitamin D3

24,25-OH- vitamin D3

45
Q

Is 1,25-OH- vitamin D3 or 24,25-OH- vitamin D3 the active form of vitamin D?

A

1,25-OH- vitamin D3

46
Q

When 1-alpha-hydroxlase acts on 25-OH-vitaminD3, what form of vitamin D made?

A

1,25-OH- vitamin D3

** active form

47
Q

When 24-alpha-hydroxlase acts on 25-OH-vitaminD3, what form of vitamin D made?

A

24,25-OH- vitamin D3

** inactive form

48
Q

Where are 1,25-OH- vitamin D3 24,25-OH- vitamin D3 located?

A

kidney

49
Q

Hypocalcemia causes 1,25-OH- vitamin D3 or 24,25-OH- vitamin D3 to be made.

A

1,25-OH- vitamin D3

50
Q

Hypocalcemia ___________ secretion of PTH

A

increases

51
Q

Increased PTH secretion causes 1,25-OH- vitamin D3 or 24,25-OH- vitamin D3 to be made.

A

1,25-OH- vitamin D3

52
Q

Low phosphate causes 1,25-OH- vitamin D3 or 24,25-OH- vitamin D3 to be made.

A

1,25-OH- vitamin D3

53
Q

High 1,25-OH- vitamin D3 causes 1,25-OH- vitamin D3 or 24,25-OH- vitamin D3 to be made.

A

24,25-OH- vitamin D3

** too much 1,25 causes negative feedback on itself

54
Q

vitamin D bind to receptor in gut which causes the production of _________

A

calbindin

55
Q

What is the role of calbindin in the small intestine?

A

carrier Ca2+ out of cell so it can be taken into blood stream

56
Q

In the intestines do Ca2+ and phosphate follow the same direction or go in opposite directions?

A

same direction

57
Q

What is the role of chief cells in the parathyroid gland?

A

secrete parathyroid hormone in response to Ca2+ levels

** Ca2+ sensors

58
Q

What is the role of oxyphil cells in the parathyroid gland?

A

provides structural integrity

59
Q

Does high or low Ca2+ levels inhibit PTH secretion?

A

high

60
Q

What is the caveat involving chief cell’s Gq receptor?

A

the release of intracellular calcium actually inhibits release of PTH

61
Q

What is the role of the parathyroid hormone?

A

raises Ca2+ levels in blood

62
Q

In the kidneys do Ca2+ and phosphate follow the same direction or go in opposite directions and why?

A

opposite

there would be too much salt and would cause kidney stones

63
Q

hypocalcemia causes __increased/decreased__ PTH secretion which causes increased ___1-alpha-hydoxylase / 24-alpha-hydroxylase___ activity which results in ___1,25-OH- vitamin D3 or 24,25-OH- vitamin D3___ to be made causing ___increased/decreased___ Ca2+ reabsorption from the GI

A

increased

1-alpha-hydoxylase

1,25-OH- vitamin D3

increased

64
Q

Osteoclasts break down bone under the stimulation of _____ in order to release Ca2+ to increase its levels in the blood

A

PTH

  • done indirectly
65
Q

How does PTH indirectly stimulate osteoclasts to breakdown bone to release ca2+?

A

osteoBLASTS have PTH receptors; when PTH binds to osteoBLASTS it releases cytokines to stimulate osteoCLASTS

66
Q

What is estrogen’s effect on osteoblasts?

A

limits its ability to produce cytokines to activate osteoclasts (why in menopause decreased estrogen causes bone damage)

67
Q

PTH causes __________ plasma Ca2+ and ________ plasma phosphate

A

increase
decrease

68
Q

What is the role of calcitonin?

A

decreases Ca2+ levels and increases phosphate levls

** opposes PTH

69
Q

What cell produces calcitonin?

A

C-cells

70
Q

How does calcitonin decrease Ca2+ levels?

A

binds to osteoclasts to prevent their function

71
Q

Vitamin D deficiency results in _____calcemia

A

hypocalcemia (decreased GI reabsorption b/c no calbindin produces to move Ca2+ out of GI cells)

72
Q

In hyperparathyroidism, what is the effect on PTH, Ca2+ and PO4- levels?

A

increased PTH
increased Ca2+
decreased PO4

(elevated Ca2+ is not feeding back to decrease PTH)

73
Q

Increased calcium can lead to kidney _________

A

stones

74
Q

increased PTH leads to what effect on bones?

A

increased degradation (due to trying to increase Ca2+ levels)

75
Q

Elevated calcium not caused by hyperparathyroidism is a result of ______

A

PTHrP (tumor of the parthyroid gland)

76
Q

PTHrP binds to osteo______ similar to PTH causing their activation

A

osteoBLASTS

(go on to activate osteoclasts via cytokines)

77
Q

Why does PTHrP cause a vicious cycle?

A

it causes release of Ca2+ from bones but that Ca2+ can feed the cancer

78
Q

PTHrP can also bind to PTH receptor in kidneys to stimulate Ca2+ _________ and phosphate _________

A

Ca2+ reabsorption = hypercalcemia
phosphate secretion

OLD "MBS 603" (22 decks)

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