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D&T 4 exam 1 > Thyroid hormones and Antithyroid drugs > Flashcards

Thyroid hormones and Antithyroid drugs Flashcards

1
Q

Iodine is present in what cells in the thyroid

A

follicular epithelial cells

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2
Q

how is iodide transported into the thyroid

A

active transport via Na/I symporter

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3
Q

what inhibits iodide transport into thyroid

A
  • uncouplers of oxidative phsophorylation (lose ATP production)
  • thiocyanate
  • perchlorate
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4
Q

Iodine trapping is stimulated by what hormone

A

TSH

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5
Q

What happens to the iodine once in follicular cells? where does it enter

A
  • oxidized by thyroid peroxidase in presence of hydrogen peroxide
  • iodide forms I2
  • follicular lumen
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6
Q

What process occurs to I2 in the follicular lumen

A

organification: thyroglobulin react with I2

- forms MIT and DIT

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7
Q

how is T3 and T4 formed?

A

coupling of MIT and DIT by thyroid peroxidase

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8
Q

thyroglobulin that contains T3 and T4 are stored as what

A

colloid in lumen of follicle

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9
Q

During the release of thyroid hormone, what role does TSH play

A
  • stimulates thyroglobulin back into follicular epithelial cells
  • lysosomal enzymes digest thyroglobulin and release T3 and T4
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10
Q

what molecule inversely modulates thyroid hormone secretion

A

iodide concentration

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11
Q

what molecule inhibits thyroid hormone release

A

lithium

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12
Q

What is the predominant thyroid hormone in blood circulation

A

T4

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13
Q

What is the most potent thyroid hormone in circulation

A

T3

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14
Q

In circulation, what is T3 and T4 bound to

A

both - TBG (thyroxine binding globulin)

T4 - Transthyretin

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15
Q

what converts T4 to T3

A

5’-deiodinase

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16
Q

where is D1 isozymes of 5’-deiodinase located

A

liver
kidney
thyroid

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17
Q

D1 isozymes of 5’-deiodinase responsibilites

A
  • majority of circulating T3

- conversion of T4 to T3

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18
Q

D2 isozymes of 5’-deiodinase is expressed where

A

brain
pituitary
skeletal
cardiac

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19
Q

D2 isozymes of 5’-deiodinase role

A
  • influences intracellular T3 levels in certain tissues
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20
Q

what inhibits D1 isozymes of 5’-deiodinase

A

propylthiouracil

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21
Q

where is 5’-deiodinase highest activity

A

liver

22
Q

what metabolizes thyroid hormones

A

P450

23
Q

How will enzyme induces of P450 impact thyroid hormone

A
  • increases conversion of T4 to T3
24
Q

what is an autoimmune disease that is the most common cause of hypothyroidism in the U.S

A

Hashimoto’s thyroiditis

25
Q

what is secondary hypothyroidism

A

pituitary hypothyroidism due to TSH deficiency

26
Q

what is the drug of choice for thyroid supplementation? why?

A

Levothyroxine (T4)

  • T4 longer duration of action
  • can be taken once a day
27
Q

What is another thyroid hormone supplementation

A

Liothyronine (T3)

28
Q

oral levothyroxine is used to treat what

A
  • hypothyrodism
  • suppression of TSH
  • Hashimoto’s thyroiditis
29
Q

IV Levothyroxine is used to treat what

A
  • Myxedma coma ( severe hypothyroidism)
30
Q

Levothyroxine interacts with what drugs

A
  1. agnets that reduce thyroxine
  2. agents alter thyroid binding globulin
  3. agents inhibit 5’-deiodinase
  4. Warfin
31
Q

name agents that reduce thyroxine bioavailability

A
  • Calcium carbonate
  • aluminum hydroxide
  • cholestyramine
  • Colesevelam
32
Q

which hormone increase serum thyroid binding globulin

A

estrogen

33
Q

What molecule decreases serum thyroid binding globulin

A

Glucocroticod

anabolic steroids

34
Q

Name agents that inhibit 5’-deiodinase

A

propylthiouracil

amiodarone

35
Q

what is the interaction of Levothyroxine and Warfin

A
  • thyroxine increases anticoagulant activity
36
Q

Adverse effects of Levothyroxine

A

cardiovascular: increase palpitations, tachycardia, increased blood pressure

37
Q

What is a common cause of hyperthyroidism

A

Grave’s disease

38
Q

What is Grave’s disease

A
  • autoimmune disorder

- antibodies bind to thyroid follicular cell or TSH receptor increasing T4 production

39
Q

what used to treat symptoms of inflammation only for hyperthyroidism

A
  • NSIADS

- aspirin

40
Q

what drugs are used to treat hyperthyroidism

A
  • Propanolol
  • propylthiouracil
  • methimazole
  • radioiodine (I131)
41
Q

radioiodine (I131) is contraindicated in who

A

pregnancy

42
Q

MOA for Propylthiouracil and Methimazole

A
  • inhibit iodide incorporation into tyrosine residues

- inhibit iodotyrosyl coupling to form iodothyronine

43
Q

what is a specific MOA for Propylthiouracil

A

inhibit peripheral 5’-deiodinase (D1) conversion of T4-T3

44
Q

what antithyroid drug is preferred during pregnancy

A
  • Propylthiouracil
45
Q

compare the half lives of the anti-thyroid drugs

A

Methimazole 6 hours

Propylthiouracil 1 hour

46
Q

side effects of Methimzaole

A

agranulocytosis

aplastic anemia

47
Q

side effect of Propylthiouracil

A

hepatic necrosis and nephritis

48
Q

what is the black box warning for Propylthiouracil

A
  • liver injury and failure
49
Q

what is iodine-131 used for

A
  1. hyperthyroidism
  2. thyroid carcinoma
  3. grave’s disease
50
Q

when is iodide used

A

preoperative to reduce vascularity of thyroid prior to surgery

51
Q

who should not use iodide and why

A

pregnant women

- induce goiter, suppress thyroid function in fetus, induce hypothyroidism

D&T 4 exam 1 (17 decks)

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