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Neuroendocrine Exam 3 > Thyroid Gland Physiology > Flashcards

Thyroid Gland Physiology Flashcards

1
Q

what is the functional unit of the thyroid gland?

A

the thyroid follicle

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2
Q

what is the thyroid follicle surrounded by?

A

a single layer of epithelial cells

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3
Q

what is the follicular lumen filled with?

A

Colloid

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4
Q

what is colloid composed of?

A

newly synthesized thyroid hormones that are attached to thyroglobulin

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5
Q

tyrosine + I2 (iodine) yields what?

A

either MIT or DIT

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6
Q

combination of 2 DIT molecules produces what?

A

T4

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7
Q

Coupling of 1 DIT molecule and 1 MIT molecule produces what?

A

T3

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8
Q

what molecule is the major secretory molecule of the thyroid gland?

A

T4

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9
Q

what process ensures that t4 is converted into the active form T3?

A

peripheral conversion

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10
Q

what is the enzyme that is responsible for converting T4 into its active form of t3?

A

deiodinase type 1 and 2*

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11
Q

what is the enzyme that is responsible for converting T4 into its inactive form of T3?

A

deiodinase type 3

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12
Q

there are some clinical states associated with a reduction in the conversion of T4 to T3. What are those states?

A

fasting, medical & surgical stress, and catabolic diseases

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13
Q

what would fasting, medical & surgical stress, and catabolic disease lead to?

A

the conversion of T4 into its inactive form using deiodinase type 3

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14
Q

what is the role of thyroglobulin?

A

it is the backbone that provides all the tyrosine residues that can be iodinated

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15
Q

how does iodide get into the cell?

A

using the Na/I synporter

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16
Q

how does iodide (I-) get converted into iodine(I2)

A

a peroxidase oxidizes it

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17
Q

how does iodine get out into the lumen?

A

the enzyme pendrin

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18
Q

all of the processes that are occurring in the lumen/apical site are mediated through what?

A

PTO

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19
Q

What is the TG-T4/T3 stored as until TSH stimulation?

A

as colloid

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20
Q

what happens if the availability of iodide is restricted?

A

the formation of T3 is favored

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21
Q

what exactly is pendrin?

A

it is a chloride/iodide pump

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22
Q

what does a mutation in the pendrin gene (PDS) cause?

A

defects in the transport across the apical membrane as well as a defect in the cochlea

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23
Q

patients who present with a pendrin syndrome, usually have what symptoms?

A

hypothyroidism with a goiter

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24
Q

whenever you have way too much iodide avaialbe because the Na I synporter is super active, what needs to happen?

A

we have to have a mechanism to limit the amount of iodide that is being used to synthesize thyroid hormone

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25
Q

how do you limit the amount of iodide that is being used to synthesize thyroid hormones?

A

we suppress the PTO (peroxidase) with PTU or we could also block the Na+ I synporter with perchlorate or thiocynate

26
Q

what is the wolff-chaikoff effect?

A

a reduction in thyroid hormone synthesis caused by a large consumption of iodide

27
Q

what disease shows a very very active thyroid gland and the uptake of radioactive iodine is really really quick?

A

grave’s disease

28
Q

what is the main binding protein for T4?

A

thyroxine-binding globulin (TBG)

29
Q

where is TBG synthesized?

A

the liver

30
Q

what is the 1/2 of t4?

A

6 days

31
Q

what test will assess the circulating levels of TBG?

A

resin uptake test

32
Q

hyperthyroidism will have what levels of T4 and resin uptake?

A

increased T4 and increased T3 resin uptake

33
Q

hypothyroidism will have what levels of T4 and resin uptake?

A

Decreased levels of T4 and decreased T3 resin uptake

34
Q

pregnant females will have what levels of TBG?

A

increased levels

35
Q

high levels of TBG will have what type of levels of T4 and resin uptake?

A

increased T4 levels and decreased T3 resin uptake

36
Q

hepatic failure will have what levels of TBG?

A

decreased levels of TBG

37
Q

decreased levels of TBG will have what levels of T4 and T3 resin uptake?

A

Decreased T4 and increased T3 resin uptake

38
Q

TSH has two effects on the thyroid gland. What are they?

A

it increases the synthesis and secretion of thyroid hormones and it has a trophic effect on the thyroid gland (makes it grow)

39
Q

What is TSH regulated by?

A

TRH and Free T3

40
Q

Are increased levels of TBG stimulatory or inhibitory of thyroid secretion?

A

stimulatory

41
Q

the thyroid hormones stimulates the synthesis of what very important protein?

A

Na+ K+ ATPase

42
Q

how do thyroid hormones affect cardiac muscle cells?

A

the myocardium will have an increased number of B1 receptors and so it will be more sensitive to stimulation by sympathetic nervous system

43
Q

what effect do the thyroid hormones have on growth?

A

growth formation/ bone maturation

44
Q

what effect do the thyroid hormones have on the CNS?

A

maturation of CNS

45
Q

What effect do the thyroid hormones have on BMR?

A

increase Na+ K+ ATPase increases O2 consumption, which increases heat production, which causes an increase in BMR

46
Q

What effect do the thyroid hormones have on metabolism?

A

net catabolic effects

47
Q

what would the blood cholesterol concentration look like in a patient with hypothyroidism?

A

it would be increased

48
Q

deficiency of thyroid hormones during the perinatal period leads to what?

A

abnormal development of synapses and decreased myelination

49
Q

what is primary hyperthyroidism?

A

grave’s disease

50
Q

what is secondary hyperthyroidism?

A

a TSH secreting tumor

51
Q

what occurs in grave’s disease?

A

thyroid-stimulating immunoglobulins stimulate the TSH receptor without TSH hormone

52
Q

What would expect the levels of TSH to be in a patient diagnosed with Grave’s disease?

A

low

53
Q

What are some signs/symptoms of graves disease?

A

exophthalmos, elevated serum free and total T4 or T3 levels, goiter, presence of circulating thyroid-stimulating immunoglobulin

54
Q

What is the most common primary hypothyroidism?

A

hashimoto’s thyroiditis

55
Q

what could be an adverse effect of over prescribing T4 to women beyond menopause?

A

development of osteoporosis

56
Q

in hoshimoto’s, what is thyroid synthesis impaired by?

A

thyroglobulin or TPO antibodies

57
Q

what would you expect the TSH levels to be of a patient with hoshimoto’s?

A

high

58
Q

what are some signs of congenital hypothyroidism?

A

feeding problems, protruding tongue, growth retardation

59
Q

what are some causes of congenital hypothyroidism?

A

iodide deficiency, maternal intake of anti-thyroid medication

60
Q

what is sheehan syndrome?

A

postpartum hypopituitarism due to necrosis of the pituitary gland

Neuroendocrine Exam 3 (19 decks)

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