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Endo Exam 1 > Thyroid > Flashcards

Thyroid Flashcards

1
Q

thyroid hormone

A

produced in follicular cells of thyroide
-requires iodine

(+) TSH
(-) T3/T4

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2
Q

thyroxine

A

T4

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3
Q

triiodothyronine

A

T3

higher action and affinity than T4

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4
Q

D1

A

deiodinates outer ring T4 - T3

-plasma membrane of peripheral tissue

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5
Q

D2

A

deiodinates outer ring of T4

-in ER in pituitary, brown fat, brain

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6
Q

D3

A

deiodinate inner ring T4 to produce rT3

  • inactivating
  • plasma memra eon skin, placenta, brain
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7
Q

thyroid hormone in blood

A

on thyroid-binding globulin

long half life

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8
Q

action of thyroid hormone

A

increase metabolism carbs, protein, lipid
necessary for growth and mental development

also increase beta-adrenergic receptor sensitivity
-increased HR, tremors, sweating

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9
Q

thyroid follicle

A

thyroid hormone synthesis in follicular epithelial cells
basal membrane - blood
apical - lumen

lumen has colloid - thyroid hormones attached to thyroiglobulin

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10
Q

thyroid hormone storage

A

extracellularly in lumen

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11
Q

thyroglobulin

A

synthesized on rER and golgi of follicle cells

-transported to lumen

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12
Q

I trap

A

Na/I cotransport
active transport of I from blood into follicle cells

low I- = increased Na/I pump activity

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13
Q

thiocyanate and perchlorate

A

block I- uptake into follicular cells

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14
Q

oxidation of I-

A

to I2

thyroid peroxidase at apical membrane

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15
Q

thyroid peroxidase

A

oxidation of I- to I2
organification I2 to tyrosines of thyroblobulin
coupling of DIT and MIT

two DIT = T4
MIT + DIT = T3

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16
Q

PTU

A

propylthyouracil - inhibits thyroid peroxidase

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17
Q

lumen rxns

A

organification and coupling

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18
Q

endocytosis of thyroglobulin

A

thyroid gland stimulation

  • iodinated thyroglbulin endocytosed to follicile cells from lumen
  • hydrolysis of T4 and T3 from thyroglobulin occurs
  • MIT and DIT are deiodinated in follicle cell (thyroid deiodinase) - recycled
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19
Q

thyroid in circulation

A

T4 and T3 bound to TBG

provides large reservoir

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20
Q

hepatic failure

A

low TBG - decreased hepatic protein synthesis

increased free thyroid levels
-negative feedback on thyroid synthesis

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21
Q

pregnancy

A

high estrogen inhibits breakdown of TBG

  • more bound thyroid
  • more production of thyroid hormones

total levels increased, free thyroid stays same
-“clinically euthyroid”

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22
Q

T3 resin uptake test

A

measure for circulating levels of TBG

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23
Q

major product of thyroid gland

A

T4 - not most active form

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24
Q

5’-iodinase

A

converts T4 to T3 intissue

tissues also convert to rT3 - inactive

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25
Q

TRH

A

released from paraventricular nuclei of hypothalamus

acts on thyrotropes of anterior pituitary to increase TSH secretion

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26
Q

TSH

A

from anterior pituitary
-increased growth thyroid gland
(-) thyroid hormones (free T3)

27
Q

TSH action on thyroid gland

A

increases synthesis of thyroid hormones

  • I uptake, oxidation, organification, coupling, endocytosis, proteolysis
  • trophic affect on gland itself
28
Q

graves disease

A

hyperthyroidism
-thyroid-stimulating immunoglobuins

low TSH, but high circulating thyroid hormones

29
Q

decreased converstion of T4 to T3

A

pregnancy, fasting, stress, hepatic and renal failure, beta-adrenergic blocking agents

30
Q

affects of T3

A

increased O2 consumption
-increased in BMR and body temperature

  • increased metabolism
  • catabolic - decreased muscle mass

increased cardiac output

  • upregulate beta-1 adrenergic receptors
  • increased heart rate and contractility
  • increased growth
  • essential for maturation of CNS
31
Q

hyperthyroid treatment

A

beta-adrenergic blocking agents

-propanolol

32
Q

graves disease

A

autoimmune
-increased thyroid-stimulating Igs

bulging eyes**

33
Q

causes of hyperthyroidism

A

graves disease
thyroid neoplasm
excessive of TRH or TSH
exogenous thyroid hormones

34
Q

low TSH levels?

A

hyperthyroidism due to:

  • graves
  • neoplasm
  • exogenous thyroid (factitious hyperthyroidism)
35
Q

high TSH levels?

A

hyperthyroidism due to:

-excess TSH or TRH

36
Q

symptoms of hyperthyroidism

A

weight loss - with increased food intake

  • excessive heat production
  • rapid heart rate (beta-1)
  • weakness

increased activity may lead to goiter

37
Q

Tx hyperthyroidism

A

propylthiouracil (PTU) - inhibits thyroid hormone synthesis

surgical removal of gland

radioactive ablation of gland w/ 131- I-

38
Q

hypothyroidism

A

most common - autoimmune destruction
-thyroditis

also due to:

  • surgical removal gland
  • I- deficiency
  • hypothalamic / pituitary failure
39
Q

thyroiditis

A

TSH will be increased

40
Q

defect in hypothalamus or pituitary

A

TSH decreased

41
Q

symptoms of hypothyroidism

A

decreased metabolism, weight gain

  • cold intolerance
  • myxedema - swelling around eyes
  • goiter
42
Q

cretinism

A

hypothyroidism in perinatal period

-growth and mental retardation

43
Q

Tx of hypothyroidism

A

TH replacement - usually T4

44
Q

serum TSH

A

most valid and useful assessment of thyroid function

45
Q

hot nodule

A

toxic adenoma

  • low TSH and gland atrophy surrounding nodule**
  • nodule products too much thyroid hormones
46
Q

toxic nodular goiter

A

multiple nodules producing thyroid

47
Q

subacute thyroiditis

A

granulomatous
-hyperthyroidism

painful gland **

viral

hyperthyroid > euthyroid > hypothyroid > euthyroid

48
Q

silent thyroiditis

A

subacute lymphocytic
-non-tender gland**
-autoimmune
transient

ex/ postpartum thyroiditis - after delivery

49
Q

euthyroid

A

normal

50
Q

hashimotos

A

primary hypothyroidism

-T-cell mediated

51
Q

pituitary insufficiency

A

secondary hypothyroidism

52
Q

tertiary hypothyroidism

A

hypothalamic disease

53
Q

hashimotos thyroiditis

A

T cell mediate autoantibodies

  • against thyroiglobulin and thyroid peroxidase
  • gradual thyroid failure

goiter, peripheral edema, constipation, HA, fatigue

  • high TSH/TRH
  • low T3/T4

Tx: levothyroxine (T4) therapy

54
Q

absence of iodine for extended period of time

A

high TSH
low T4
low T3

55
Q

TH administration

A

decreased TSH

  • decreased iodide uptake
  • decreased thyroglobulin levels
  • gland atrophy
56
Q

radioactive iodine scan

A

to see if thyroid hormones are being made

don’t do if breastfeeding

57
Q

sheehans syndrome

A

hypopituitarism caused by ischemic necrosis due to blood loss and hypovolemic shock during and after childbirth

58
Q

TRH

A

stimulate TSH and prolactin release

hard to sample the release hormone levels - too invasive to brain arterial capillary plexus

59
Q

euthyroid sick syndrome

A

critically ill patients
thyroid hormone decrease

decrease in T3
increase in rT3 - inactive

adaptive to protect body during illness

60
Q

estrogen

A

from contraceptive

  • may cause increased TBG
  • transient hyperthyroidism
61
Q

mechanism of thyroxine

A

binds cytoplasm receptor

  • complex diffuses to nucleus
  • affects transcription
62
Q

hypothyroidism

A 
bradycardia
constipation
peripheral edema
muscle weakness
small thyroid
periorbital edema
puffy face
hair loss
63
Q

hyperthyroid

A 
bulging eyes- exopthalmos
tachycardia
weight loss
diarrhea
hyperreflexia

Endo Exam 1 (10 decks)

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