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Endocrine > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

where are the thyroid hormones stored

A

in follicular lumen (colloid) in thyroid gland

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2
Q

which is synthesized faster T4 or T3

A

T4 so more is produced and secreted (20:1)

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3
Q

what enzyme converts T4 to T3 in the periphery

A

deiodinase, most T3 comes from peripheral conversion

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4
Q

what decreases the conversion of T4 to T3

A

Fasting, Aging, Pregnancy, Hepatic and renal failure, Beta-blockers, hypothyroid

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5
Q

what increases conversion of T4 to T3

A

hyperthyroid, obesity, cold exposure

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6
Q

how is thyroid hormones transported in the blood

A

99% bound to proteins

1% unbound, free

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7
Q

main binding proteins of T3 and T4

A

TBG, 70%, made in liver, higher affinity for T4 than T3 binds 1 each

  • transthyretin
  • albumin
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8
Q

T3 resin uptake test. what decreases T3 resin uptake

A

increase in TBG or a decrease in endogenous T3

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9
Q

T3 resin uptake test, what increases T3 resin uptake

A

When there is a decrease in TBG or an increase in endogenous T3

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10
Q

what does pregnancy do to TBG levels

  • effect on T3 and T4 syn
  • is this normal?
A

increases it, which decreases free T3 and T4 and stimulates synthesis of more T3 and T4
-increases levels of T3 and T4 but levels of free physiologyically active Thyroid hormones are normal
(person is clinically “euthyroid”)

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11
Q

hepatic failure and thyroid hormone syn

A

hepatic failure decreases TBG, which increases free T3 and T4
-negative feedback inhibits syn of more T3 and T4

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12
Q

which hormone has a negative feedback on the anterior pituitary

A

too much T3 inhibits the secretion of TSH from the AP

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13
Q

what is the second messenger for TSH

A

cAMP

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14
Q

what effects does TSH have on thyroid gland?

A

increases synthesis and secretion of thyroid hormones

trophic effect on thyroid gland

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15
Q

Graves disease and TSH levels

A

graves disease occurs when thyroid-stimulating immunoglobulins bind TSH receptor on thyroid cell and cause unregulated overproduction of thyroid hormones

-TSH levels are low bc T3 neg inhibits AP from releasing TSH

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16
Q

factors that stimulate thyroid hormone secretion

A

pregnancy (increased TBG decreases free T3 and T4 so make more)
TSH
thyroid stimulating Igs

17
Q

how is heat production increased with thyroid hormones

A

thyroid hormones stimulate synthesis of Na+/K+ ATPase which leads to increased O2 consumption so BMR and heat production increase

18
Q

what does TH stimulate in cardiac muscle cells

A

myosin, B1-adrenergic receptors and Ca+ ATPase

-thyroid increases HR and contractility

19
Q

effect of TH on liver and adipose tissue

A

induce synthesis of metabolic enzymes, so alters carb, fat and protein metabolism

20
Q

T3 effect on growth

A

growth formation and bone maturation

21
Q

T3 effect on metabolsim

A 
increase:
glucose absorption
glycogenolysis
gluconeogenosis
lipolysis
protein synthesis and degradation (net catabolic)
    -decreased muscle mass
22
Q

T3 effect on cardiovascular system

A

increase cardiac output

23
Q

hypothyroidism ___ blood cholesterol

A

increases

24
Q

hypothyroid patients can suffer from blindness and yellowing of skin. why is this?

A

TH stimulate lipid metabolism and this is required for conversion of carotene to vitamin A

25
Q

thyroid effect on HR and contractility

A

increased thyroid hormone levels increases myocardium number of B1 receptor

  • makes it more sensitive to stimulation by symp NS
  • increases HR and contractility
26
Q

TH effect on CNS

A

critical for correct CNS development during perinatal period

27
Q

TH effect on intestine

  • Excess
  • Deficiency
A 
excess = diarrhea
deficiency = constipation
28
Q

overprescribing T4 in women beyond menopause can contribute to what

A

development of osteoporosis

29
Q

hashimoto’s thyroiditis

A

TH synthesis blocked by antibodies which leads to decreased T3,T4 secretion

  • increases TSH from AP
  • causes goiter bc of trophic effect
30
Q

cretinism

A

hypothyroidism in perinatal period for baby

-growth and mental retardation, jaundice, resp difficulty, protruding tongue

31
Q

graves disease signs

A

exophthalmos, abnormal protrusion of eyeball

  • elevated T4 and T3 with decreased TSH
  • circulating thyroid stim immunoglobulins
32
Q

primary hypothyroidism causes

A
  • lack of adequate iodine in the diet

- hashimoto disease

Endocrine (14 decks)

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