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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
TRH
released from paraventricular nuclei of hypothalamus acts on thyrotropes of anterior pituitary to increase TSH secretion
26
TSH
from anterior pituitary -increased growth thyroid gland (-) thyroid hormones (free T3)
27
TSH action on thyroid gland
increases synthesis of thyroid hormones - I uptake, oxidation, organification, coupling, endocytosis, proteolysis - trophic affect on gland itself
28
graves disease
hyperthyroidism -thyroid-stimulating immunoglobuins low TSH, but high circulating thyroid hormones
29
decreased converstion of T4 to T3
pregnancy, fasting, stress, hepatic and renal failure, beta-adrenergic blocking agents
30
affects of T3
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
hyperthyroid treatment
beta-adrenergic blocking agents | -propanolol
32
graves disease
autoimmune -increased thyroid-stimulating Igs bulging eyes**
33
causes of hyperthyroidism
graves disease thyroid neoplasm excessive of TRH or TSH exogenous thyroid hormones
34
low TSH levels?
hyperthyroidism due to: - graves - neoplasm - exogenous thyroid (factitious hyperthyroidism)
35
high TSH levels?
hyperthyroidism due to: | -excess TSH or TRH
36
symptoms of hyperthyroidism
weight loss - with increased food intake - excessive heat production - rapid heart rate (beta-1) - weakness increased activity may lead to goiter
37
Tx hyperthyroidism
propylthiouracil (PTU) - inhibits thyroid hormone synthesis surgical removal of gland radioactive ablation of gland w/ 131- I-
38
hypothyroidism
most common - autoimmune destruction -thyroditis also due to: - surgical removal gland - I- deficiency - hypothalamic / pituitary failure
39
thyroiditis
TSH will be increased
40
defect in hypothalamus or pituitary
TSH decreased
41
symptoms of hypothyroidism
decreased metabolism, weight gain - cold intolerance - myxedema - swelling around eyes - goiter
42
cretinism
hypothyroidism in perinatal period | -growth and mental retardation
43
Tx of hypothyroidism
TH replacement - usually T4
44
serum TSH
most valid and useful assessment of thyroid function
45
hot nodule
toxic adenoma - low TSH and gland atrophy surrounding nodule** - nodule products too much thyroid hormones
46
toxic nodular goiter
multiple nodules producing thyroid
47
subacute thyroiditis
granulomatous -hyperthyroidism painful gland ** viral hyperthyroid > euthyroid > hypothyroid > euthyroid
48
silent thyroiditis
subacute lymphocytic -non-tender gland** -autoimmune transient ex/ postpartum thyroiditis - after delivery
49
euthyroid
normal
50
hashimotos
primary hypothyroidism | -T-cell mediated
51
pituitary insufficiency
secondary hypothyroidism
52
tertiary hypothyroidism
hypothalamic disease
53
hashimotos thyroiditis
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
absence of iodine for extended period of time
high TSH low T4 low T3
55
TH administration
decreased TSH - decreased iodide uptake - decreased thyroglobulin levels - gland atrophy
56
radioactive iodine scan
to see if thyroid hormones are being made don't do if breastfeeding
57
sheehans syndrome
hypopituitarism caused by ischemic necrosis due to blood loss and hypovolemic shock during and after childbirth
58
TRH
stimulate TSH and prolactin release hard to sample the release hormone levels - too invasive to brain arterial capillary plexus
59
euthyroid sick syndrome
critically ill patients thyroid hormone decrease decrease in T3 increase in rT3 - inactive adaptive to protect body during illness
60
estrogen
from contraceptive - may cause increased TBG - transient hyperthyroidism
61
mechanism of thyroxine
binds cytoplasm receptor - complex diffuses to nucleus - affects transcription
62
hypothyroidism
``` bradycardia constipation peripheral edema muscle weakness small thyroid periorbital edema puffy face hair loss ```
63
hyperthyroid
``` bulging eyes- exopthalmos tachycardia weight loss diarrhea hyperreflexia ```

Endo Exam 1 (10 decks)

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