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Year 2 Pharmacology > Thyroid and antithyroid agents > Flashcards

Thyroid and antithyroid agents Flashcards

1
Q

where does thyroid hormone synthesis take place?

A

cell itself and colloid

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2
Q

how does iodide get into the thyroid gland?

A

sodium / iodide symporter (NIS)

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3
Q

what enzyme is responsible for converting iodide to iodine?

A

peroxidase

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4
Q

what is iodide organification? what are the results?

A

iodination of tyrosine residues within thyroglobulin molecule

monoiodotyrosine (MIT)
diiodotyrosine (DIT)

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5
Q

how are the thyroid hormones formed?

A

molecules of MIT and DIT are combined to form:

MIT plus DIT - T3
DIT plus DIT - T4

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6
Q

what is the typical ratio of thyroid hormones?

A

T4: T3 - 5:1

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7
Q

the majority of thyroid hormones are bound to what molecule?

A

thyroxine bound globulin (TBG)

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8
Q

what is the MOA of thyroid hormone in the absence of thyroid hormone?

A

homodimer of receptor is sitting on response element of gene - NO activation of transcriptional processes

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9
Q

what is the MOA of thyroid hormone in presence of thyroid hormone?

A

hormone is transported into cell

RXR and TR form heterodimer and increases gene transcription

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10
Q

what is the function of 5’-deiodinase (5’-DI)?

A

conversion of T4 to T3

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11
Q

what is the result of inhibition of 5’-DI?

A

hypothyroidism type symptoms

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12
Q

what is the regulation of thyroid secretion? what type of feedback is involved?

A

TRH - TSH

TSH promotes synthesis of T4 and T3

negative feedback

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13
Q

what are the result of high blood concentrations of iodide on hormone synthesis? low blood levels?

A

inhibition

promotion of synthesis

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14
Q

what are the metabolic effects of thyroid hormone on fat?

A
  1. decrease circulating cholesterol via increase in LDLr expression
  2. increased lipolysis
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15
Q

what are the metabolic effects of thyroid hormone on carbohydrates?

A
  1. increased intestinal absorption of carbohydrates
  2. increased glycolysis
  3. increased gluconeogenesis
  4. increased insulin secretion
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16
Q

what are the metabolic effects of thyroid hormone on protein?

A

increased protein synthesis and catabolism

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17
Q

what are the metabolic effects of thyroid hormone on vitamins?

A

increase need and usage for cofactors to enzymes as a result of a general increase in enzyme secretion

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18
Q

definition: myxedema

when is it seen in relation to thyroid metabolism?

A

puffy, baggy eyes from retention of fluids in interstitial spaces

hypothyroidism

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19
Q

what are the causes of hypothyroidism?

A 
congenital 
autoimmune thyroiditis (hashimoto's) 
iodide deficiency
20
Q

what are the treatment options for hypothyroidism?

A

levothyroxine (T4)
liothyronine (T3)
liotrix (mixture T3 and T4)

21
Q

what is the treatment of choice for hypothyroidism? why?

A

levothyroxine

more stable, low cost, long half life, more physiological

22
Q

what is the MOA of thyroid hormone?

A

activation of T3 receptors

23
Q

what considerations should be made when treating elderly patients for hypothyroidism? why?

A

must check for underlying CV disease (decreasing contractility and BP)

hypothyroidism is protective for potential coronary artery disease

24
Q

what are the adverse effects of thyroid hormone in children?

A

restlessness, insomnia, accelerated bone maturation

25
Q

what are the adverse effects of thyroid hormone in adults?

A

nervousness, heat intolerance, palpitations, tachycardia, weight loss

26
Q

which thyroid hormone is more potent? why?

A

T3

already in ligand-active form

27
Q

what is the mechanism of grave’s disease? what are the levels of TSH?

A

autoantibodies stimulate TSH receptors and increase the production of T3 and T4

TSH levels will be low

28
Q

what are the thioamide antithyroid agents for hyperthyroidism?

A

methimazole

propylthiouracil (PTU)

29
Q

what is the MOA of the antithyroid agents?

A

inhibition of peroxidase reaction, iodineorganification, and coupling of iodotyrosines

30
Q

which antithyroid agent is appropriate for use in pregnant women? why?

A

propylthiouracil (PTU)

75% protein binding

31
Q

what is the significant adverse effect of PTU?

A

severe hepatitis

32
Q

what are the iodide antithyroid agents?

A

potassium iodide

lugol’s solution

33
Q

what is the MOA of the iodide antithyroid agents?

A
  1. inhibition of TGB proteolysis

2. decreases vascularity, size, and fragility of hyperplastic gland

34
Q

which class of antithyroid agents are useful against iodide storm? why?

A

iodide agents

rapid onset

35
Q

which class of antithyroid agents are useful for hyperplastic gland and preop preparation? why?

A

iodide agents

decreases vascularity, size, and fragility of hyperplastic gland

36
Q

what is the radioactive antithyroid agent? what is the MOA?

A

radioative iodine 131-I

destruction of parenchymal cells

37
Q

what are the anion inhibitor antithyroid agents?

A

perchlorate
pertechenate
thiocyanate

38
Q

what is the MOA of the anion inhibitor antithyroid agents?

A

inhibition of energy dependent uptake of iodide into the thyroid cells that is mediated by sodium / iodide symporter

39
Q

what is the main adverse effect of radioactive iodine 131-I?

A

hypothyroidism

40
Q

what agents can be used to treat iodide-induced hyperthyroidism (eg amiodarone induced thyrotoxicosis)

A

anion inhibitors

41
Q

what are the key adjuncts antithyroid agents?

A

propanolol
diltiazem
barbiturates
bile acid sequestrants

42
Q

what are the clinical uses of beta blockers for hyperthyroidism?

A

adjunct to control tachycardia, HTN, aF

43
Q

what is the clinical use for diltiazem?

A

control tachycardia in asthmatic

44
Q

what is the clinical use for barbiturates?

A

increase T4 metabolism

45
Q

what is the clinical use for bile acid sequestrants?

A

increase biliary T4 excretion

Year 2 Pharmacology (70 decks)

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