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Therapeutics > module 2 lecture 2 > Flashcards

module 2 lecture 2 Flashcards

1
Q

What are the two types of thyrroid hormones

A

thyroxine (T4) and triiodothyronine (T3)

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2
Q

Which thyroxine is produced more? which is more potent?

A

T4 is produced 10x more
T3 is more potent

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3
Q

What are the 4 physiological effects of thyroid hormones

A

Growth and development
metabolism
thermogenesis
CV effects

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4
Q

Absent T3 can cause

A

cretinism

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5
Q

how does thyroid hormone affect growth and development

A

Promotes protein sythesis and brain development

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6
Q

is thyroid hormone anabolic or catabolic?

A

BOTH! anabolic at normal concentrations, catabolic at hyperthyroid levels

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7
Q

How does thyroid hormone affect metabolism

A

It increases the basal metabolic rate and O2 consumption

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8
Q

How does thyroid affect thermogenesis

A

Increases the resting heat production
Inability to adjust temperatures is a symptom of both hyper and hypo thyroidism

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9
Q

effect of thyroid hormone on cardiovascular symptoms

A

increases catecholamine sensitivity (epinephrine norepinephrine etc) leading to rapid HR

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10
Q

1st step of thyroid hormone synthesis (where does this take place?)

A

Dietary iodine (I2) to iodide (i-) in stomach

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11
Q

second step of thyroid hormone synthesis

A

iodide is actively transported into the cell by NIS (Na I symporter)

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12
Q

third step of thyroid synthesis (where does this take place?)

A

In the follicular cell, iodide passes down its electrochemical gradient and into the follicular colloid. It is oxidized by thyroid peroxidase to I 0 at apical membrane

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13
Q

4th step of thyroid synthesis

A

Iodide free thyroglobulin is transported to the apical membrane

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14
Q

5th step of thyroid synthesis

A

Thyroglobulin is iodinated by thyroid peroxidase at one or two positions forming the hormone precursors monoiodotyrosine (MIT) and diiodotyrosine (DIT) This step is called iodide organification.

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15
Q

6th step of thyroid synthesis

A

MIT + DIT or
DIT+DIT will for T3 and T4 respectively.

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16
Q

7th step of thyroid synthesis

A

thyroid hormone containing thyroglobulin is retrieved back to cytosol by pinocytosis

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17
Q

8th and final step of thyroid synthesis

A

Lysosomal exopeptidases cleave T4 (or T3) from thyroglobulin. The hormone is then released into circulation where T4 can be converted to more active T3 by 5 deiodinase

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18
Q

hypothalamus- pituitary-thyroid axis

A

hypothalamus
! TRH
anterior pituitary
! TSH
thyroid glabd
!
T4 and T3

T4 and T3 have a negative feedback loop on anterior pituitary and hypothalamus

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19
Q

How to distinguish toxic goiter from non-toxic goiter

A

Toxic goiters are hyper thyroidic. they produce a lot of thyroid hormones.

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20
Q

What are the ways thyroid is transported in plasma

A

TBG
transthyretia
albumin

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21
Q

transport proteins have greater affinity to T3 or T4?
What percent of T4 is free?
Which one has a longer half life? T3 or T4?
Which one has a more rapid onset?

A

Greater affinity to T4
0.04 % is free
T4 has a longer half life
T3 has a more rapid onset

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22
Q

T4 is converted to T3 by

A

5 ‘ deionidase

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23
Q

In excretion via bila, T4 can be converted into ____ &_____. T3 can be converted into _____

A

T3 active or rT3 (inactive)
T3 can be inactivated by converting to 3’ T2

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24
Q

Symptoms of hypothyroidism

A

low metabolic rate (fatigue, mental fullness)
defective thermoregulation (cold)
non-toxic goiter
dwarfism or cretinism

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25
Q

What is the most common cause of hypothyroidism

A

Hashimotos thyroiditis

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26
Q

What is hashimotos thyroiditis

A

Most common cause of hypothyroidism that is caused by an autoimmune disease that destroys your thyroid glands.

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27
Q

Symptoms of hyperthyroidism

A

Excessive metabolism (always hot and losing weight)
increased HR and vascular output

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28
Q

What is the most common cause of hyperthyroidism

A

Graves disease

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29
Q

What is graves disease

A

Most common autoimmune thyroid stimulating IgG .

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30
Q

What are some drugs used in Thyroid hormone replacement therapy (hypothyroidism)

A

Levothyroxine (T4)
Liothyrionine (T3)
Liotrix

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31
Q

Levothyroxine (T4) characteristics

A

Converted to T3 intracellularly
slow onset, long half life (7-days)
takes 6-8 weeks to reach steady state levels

32
Q

Liothyronine (T3) characteristics

A

Rapid onset, short duration of action (24 hrs)
greater risk of vardiotoxicity

33
Q

Liotrix characteristics

A

4:1 mixture of T4 & T3, more expensive
not shown to be more effective that T4 alone.

34
Q

What are some treatment options for hyperthyroidism

A

Thioamides
I 131
Iodide

35
Q

What are some thioamide drugs

A

Methimazole, propylthiouracil

36
Q

how do thioamides work in hyperthyroidism?

A

they inhibit thyroid peroxidases
(this blocks iodine organification and coupling of iodotyrosines)
slow onset

37
Q

How does I 131 work in treating hyperthyroidism? how is it administered?

A

localized destruction of thyroid follicles
administered orally as Na 131 I

38
Q

issues with 131 I

A

hypothyroidism occurs in 80% of patients and includes a potential increase in certain cancers

39
Q

How does Iodide treat hyperthyroidism

A

large doses of I- inhibit its own uptake. iodide large doses inhibit thyroide synthesis and release .

40
Q

Can iodide be used long term for hyperthyroid treatment?

A

No

41
Q

what is the most sensitive index for hyperthyroidism and the gold standard for testing

A

TSH test

42
Q

Which test is the most accurate

A

Free T4 (may be normal in mild thyroid)

43
Q

What are the tests of autoimmunity

A

ATgA
TPO-Ab
TRAb

44
Q

Does low or high TSH indicate hyperthyroidism

A

Low

45
Q

does low or high FT4 indicate hyperthyroidism

A

High

46
Q

What are the 4 causes of drug induced hyperthyroidism

A

Iodinated cpds
Amiodarone
Interferon a &b
Li

47
Q

What are 3 treatments for hyperthyroidism

A

Thioamides (propylthiouracil, methimazole)
Radioactive iodine
Surgery

48
Q

Which thioamide drug has a longer half life

A

Methimazole

49
Q

What is the dosing for the thioamide drugs

A

Daily for methimazole, Q 8-12 hrs for PTU

50
Q

Which thioamide drug blocks T4->T3 conversion

A

PTU

51
Q

what trimesters can the thioamide drugs be used

A

PTU-1st trimester
Methimazole- 2n and 3rd trimester

52
Q

Which thioamide drug is preferred in lactation

A

Methimazole

53
Q

Which thioamide drug is more potent

A

methimazole

54
Q

Which thioamide drug has a black box warning

A

PTU- hepatic failure

55
Q

Initial PTU dosing

A

50-150 mg TID

56
Q

Initial methimazole dosing

A

Free T4 1-1.5x ULN 5-10
Free T4 >1.5-2x ULN 10-20
Free T4 > 2x ULN 30-40

57
Q

What is the maintenance dose for methimazole

A

5-15 mg/day

58
Q

Maintenance dosing for PTU

A

50 mg BID or TID

59
Q

MAX dosing PTU

A

1200 mg/day

60
Q

MAX dosing for methimazole

A

60 mg/day

61
Q

Thioamide adverse effects

A

GI upset, nausea, vomiting
rash (wheals, hive, SOB)
Agranulocytosis (If neutrophil drops below 500 d/c immediately)
Hepatitis

62
Q

RAI absolute contraindications

A

Pregnant or Nursing

63
Q

When can we use B blockers for hyperthyroidism

A

Only for short term to control symptoms. HR>90 BPM

64
Q

what are some cardio selective b blockers for hyperthyroidism

A

propanolol (partially blocks T4->T3 conversion)
metoprolol
atenolol

65
Q

When should we use calcium channel blockers instead of b blockers for hyperthyroidism

A

bronchiospasms

66
Q

What are some calcium channel blockers

A

Diltiazem or verapamil

67
Q

What agents should we avoid when treating hyperthyroidism with B blockers

A

Agents with sympathomimetic activity
(acebutolol, carteolol, penbutolol, pindolol)

68
Q

What are some thyroid supplements for hypothyroidism

A

Levothyroxine (T4)
Liothyronine (T3)
Desiccated thyroid

69
Q

Name levothyroxine drugs

A

Tirosint, synthroid, levoxyl, unithyroid

70
Q

Liothyronine (T3) drugs

A

Cytomel, triostat

71
Q

Desiccated thyroid drug name

A

Armour thyroid

72
Q

First choice of treatment for hypothyroid patients

A

levothyroxine

73
Q

Blackbox warning for Levothyroxine

A

In euthyroid patients, thyroid supplements are ineffective for weight loss.High doses may produce life threatening toxic effects

74
Q

How does levothyroxine help hypothyroidism

A

Converts T4 to T3. It provides necessary hormone without bolus effect of T3. Long half life allows for daily dosing.

75
Q

Patient counseling for levothyroxine

A

Take on an empty stomach (60 min before breakfast) or 4 hr after eating before bed

Therapeutics (46 decks)

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