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Pharm Exam 4 > Thyroid Hormones > Flashcards

Thyroid Hormones Flashcards

1
Q

What is required for thyroid hormone synthesis?

A

Iodine

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2
Q

If iodine is too high, what happens?

A

Transient inhibition of TH synthesis

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3
Q

What stimulates release of TSH from hypothalamus?

A

Thyrotropin releasing hormone (TRH)

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4
Q

Role of TSH

A

Regulate synthesis/release of TH from thyroid gland

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5
Q

Thyroid Hormone Transportation

A

Protein bound, only free form is active

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6
Q

Thyroid Hormone Metabolism

A

Peripheral deiodination w/ reutilization of iodine

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7
Q

Thyroid Hormone Excretion

A

Excreted in bile

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8
Q

Most TH secreted

A

T4

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9
Q

Which TH hormone is more protein bound?

A

T4

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10
Q

Which TH hormone is more active form?

A

T3

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11
Q

T3 half-life

A

1-2 days

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12
Q

T4 half-life

A

6-7 days

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13
Q

Which TH is more potent?

A

T3

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14
Q

Most TH in blood

A

T4 (ratio 4:1 of free T4:T3)

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15
Q

Ratio of total T4:T3 in blood

A

100:1

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16
Q

T3 and T4 MOA

A

Act on same receptor to regulate nuclear transcription and specific TH hormone response elements in DNA

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17
Q

Effects of TH

A

Growth & development (increase metabolism)

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18
Q

Primary causes of hypothyroidism

A

Hashimoto’s thyroiditis
Dietary deficiency of iodine
Excess goitrogens
Congenital defect

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19
Q

Secondary causes of hypothyroidism

A

Pituitary or hypothalamic failure

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20
Q

Cretinism

A

Infant hypothyroidism

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21
Q

Complications of Cretinism

A

Present @ birth
Dwarfism
Mental retardation
Thick & dry skin, lethargy, cold

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22
Q

Signs/symptoms of adult hypothyroidism

A 
Edema
Baggy eyes
Decrease HR
Decrease metabolism 
Cold intolerance
Hypercholesterolemia
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23
Q

How is adult hypothyroidism diagnosed?

A

Symptoms AND lab tests

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24
Q

What is myxedema coma?

A

Severe, untreated hypothyroidism, usually w/ precipitating stress

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25
Q

Symptoms of myxedema coma

A 
Hypotension
Hyponatremia 
Hypoglycemia 
Hypoventilation
Hypothermia
Coma
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26
Q

Causes of hyperthyroidism

A 
Grave’s disease (diffuse goiter)
Thyroid Adenoma (toxic modular goiter)
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27
Q

Hyperthyroidism signs/symptoms

A 
Increased met. 
Increased appetite
Catecholamine potentiation
Anxiety
Tachy
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28
Q

How is hyperthyroidism diagnosed?

A

Lab tests

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29
Q

What is a thyroid storm?

A

Severe hyperthyroidism; triggered by thyroid surgery, stress of independent illness, trauma, infection, therapeutic I admin

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30
Q

Thyroid storm symptoms

A 
Fever
Tachy
Weakness
Apathy 
Delirium
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31
Q

Similar to endogenous T4 that is then converted to T3 in the body

A

Levothyroxine

32
Q

Levothyroxine onset

A

Slow

33
Q

Levothyroxine DOA

A

Long (due to protein binding)

34
Q

Levothyroxine use

A

Hypothyroidism
Myxedema coma (via IV)
Thyroid cancer (to suppress TSH)
TH replacement after thyroid gland removal

35
Q

Levothyroxine Dose

A

100 ug/day

36
Q

Similar to endogenous T3 and given fully active and rapidly degraded

A

Liothyronine

37
Q

Liothyronine onset

A

Rapid

38
Q

Liothyronine DOA

A

Short (minimal protein bound)

39
Q

Liothyronine use

A 
Short term prior/after radio-iodine treatment 
Thyroid cancer (short term TSH suppression while waiting for T4 to take effect)
40
Q

Liothyronine dose

A

25ug 4x/day

41
Q

How to dose TH for CV disease patients?

A

Small dose and slowly increased while monitoring CV function; too abrupt increase strains weak hearts

42
Q

TH consideration in pregnant patients

A

Continue use, even increase dose due to increased demand

43
Q

Treatment regimen for myxedema coma

A

Start w/ IV Levo then maintain w/ oral Levo

44
Q

Drug interactions of TH

A

Levo accelerates degradation of vitamin K clotting factors and increases cardiac sensitivity to catecholamines

45
Q

TH Thioamide drugs

A

Methimazole

Propylthiouracil

46
Q

Thioamides MOA

A

Inhibits peroxidase but NOT release of preformed THs

47
Q

Thioamides Pharmacokinetics

A

Oral, rapidly cleared from circulation to thyroid
Excreted in urine
Latency period before effects are noted

48
Q

Thioamides use

A

Gain initial control of rapid TH production

Thyroid storm

49
Q

Thioamide side effects

A

Agranulocytosis (sore throat + fever)

Skin rash, arthralgia, myalgia, hypothyroidism/goiter

50
Q

Which Thioamide is more potent?

A

MMI (10X more)

51
Q

MMI dose

A

1x/day

52
Q

Which drug has a longer plasma life and DOA?

A

MMI

53
Q

Which thioamide drug is safe during first trimester of pregnancy?

A

PTU

54
Q

Why is MMI the preferred drug?

A

No liver toxicity risk

55
Q

MMI MOA

A

Inhibits peroxidase and TH synthesis

56
Q

PTU dose

A

2-4x/day

57
Q

PTU risks

A

Severe liver toxicity/failure

58
Q

PTU MOA

A

Inhibits peroxidase

Inhibits conversion of T4 to T3 in PERIPHERY

59
Q

Potassium Iodide MOA

A

Inhibit synthesis and release of THs

NO effect on T4 to T3 conversion

60
Q

Potassium Iodide PK

A 
Acute inhibition (rapid onset & effect)
Decrease size and vascularity of thyroid gland
61
Q

Potassium Iodide uses

A

Thyroid storm
10 days before thyroidectomy
Radiation emergencies

62
Q

Potassium Iodide side effects

A

Sore throat, teeth, gums
Brassy taste
Burning mouth sensation

63
Q

Potassium Iodide contraindications

A

Long term use

Prior to radiation therapy

64
Q

Potassium Iodide Dose/Route

A

Potassium iodide - oral
Sodium iodide - IV
Lugol’s solution - prior to thyroidectomy

65
Q

Radioactive Iodine MOA

A

85% beta radiation for local tissue destruction

15% gamma radiation for Dx and imaging

66
Q

Radioactive Iodine uses

A

Small dose - tracer studies of iodine uptake

Large dose - no surgical destruction of thyroid tissue

67
Q

Why would thyroid drugs be combined with radio-iodine?

A

Thioamides maximize radio-iodine uptake due to decreased TH —> increased TSH —> increased radio-iodine uptake and decrease risk of thyroid storm

68
Q

Benefits of radio-iodine

A

Cheap, safe, effective

69
Q

Radio-iodine contraindications

A

Children
Pregnancy
Nursing

70
Q

Radio-iodine side effects

A

Thyroiditis
Salivary adenitis
Inflammation at site of radiation

71
Q

What is a partial thyroidectomy’s purpose?

A

Alternative to radio-iodine; typically for thyroid cancer, Grave’s disease

Rare due to morbidity risk

72
Q

Strategies before partial thyroidectomy

A

euthyroid 6 wk prior to surgery w/ thioamide
Iodine therapy 2 wks before surgery

Levo to treat hypothyroidism s/p surgery

73
Q

Treatment of hyperthyroidism in young pt

A

MMI

74
Q

Treatment of hyperthyroidism in old pt

A

Radio-iodine

75
Q

Treatment of hyperthyroidism in pregnant pt

A

PTU

76
Q

Treatment of hyperthyroidism in Grave’s disease

A

Surgery

77
Q

Treatment of Thyroid Storm

A

Thioamides - decrease release of formed hormones

PTU - prevent TH synthesis & conversion of T4 to T3

GCs - prevent shock + slows T4 to T3 conversion @ high doses

Propranolol - symptomatic relief + slows T4 to T3 conversion

Pharm Exam 4 (8 decks)

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