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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
Symptoms of myxedema coma
``` Hypotension Hyponatremia Hypoglycemia Hypoventilation Hypothermia Coma ```
26
Causes of hyperthyroidism
``` Grave’s disease (diffuse goiter) Thyroid Adenoma (toxic modular goiter) ```
27
Hyperthyroidism signs/symptoms
``` Increased met. Increased appetite Catecholamine potentiation Anxiety Tachy ```
28
How is hyperthyroidism diagnosed?
Lab tests
29
What is a thyroid storm?
Severe hyperthyroidism; triggered by thyroid surgery, stress of independent illness, trauma, infection, therapeutic I admin
30
Thyroid storm symptoms
``` Fever Tachy Weakness Apathy Delirium ```
31
Similar to endogenous T4 that is then converted to T3 in the body
Levothyroxine
32
Levothyroxine onset
Slow
33
Levothyroxine DOA
Long (due to protein binding)
34
Levothyroxine use
Hypothyroidism Myxedema coma (via IV) Thyroid cancer (to suppress TSH) TH replacement after thyroid gland removal
35
Levothyroxine Dose
100 ug/day
36
Similar to endogenous T3 and given fully active and rapidly degraded
Liothyronine
37
Liothyronine onset
Rapid
38
Liothyronine DOA
Short (minimal protein bound)
39
Liothyronine use
``` Short term prior/after radio-iodine treatment Thyroid cancer (short term TSH suppression while waiting for T4 to take effect) ```
40
Liothyronine dose
25ug 4x/day
41
How to dose TH for CV disease patients?
Small dose and slowly increased while monitoring CV function; too abrupt increase strains weak hearts
42
TH consideration in pregnant patients
Continue use, even increase dose due to increased demand
43
Treatment regimen for myxedema coma
Start w/ IV Levo then maintain w/ oral Levo
44
Drug interactions of TH
Levo accelerates degradation of vitamin K clotting factors and increases cardiac sensitivity to catecholamines
45
TH Thioamide drugs
Methimazole | Propylthiouracil
46
Thioamides MOA
Inhibits peroxidase but NOT release of preformed THs
47
Thioamides Pharmacokinetics
Oral, rapidly cleared from circulation to thyroid Excreted in urine Latency period before effects are noted
48
Thioamides use
Gain initial control of rapid TH production | Thyroid storm
49
Thioamide side effects
Agranulocytosis (sore throat + fever) | Skin rash, arthralgia, myalgia, hypothyroidism/goiter
50
Which Thioamide is more potent?
MMI (10X more)
51
MMI dose
1x/day
52
Which drug has a longer plasma life and DOA?
MMI
53
Which thioamide drug is safe during first trimester of pregnancy?
PTU
54
Why is MMI the preferred drug?
No liver toxicity risk
55
MMI MOA
Inhibits peroxidase and TH synthesis
56
PTU dose
2-4x/day
57
PTU risks
Severe liver toxicity/failure
58
PTU MOA
Inhibits peroxidase | Inhibits conversion of T4 to T3 in PERIPHERY
59
Potassium Iodide MOA
Inhibit synthesis and release of THs NO effect on T4 to T3 conversion
60
Potassium Iodide PK
``` Acute inhibition (rapid onset & effect) Decrease size and vascularity of thyroid gland ```
61
Potassium Iodide uses
Thyroid storm 10 days before thyroidectomy Radiation emergencies
62
Potassium Iodide side effects
Sore throat, teeth, gums Brassy taste Burning mouth sensation
63
Potassium Iodide contraindications
Long term use | Prior to radiation therapy
64
Potassium Iodide Dose/Route
Potassium iodide - oral Sodium iodide - IV Lugol’s solution - prior to thyroidectomy
65
Radioactive Iodine MOA
85% beta radiation for local tissue destruction | 15% gamma radiation for Dx and imaging
66
Radioactive Iodine uses
Small dose - tracer studies of iodine uptake | Large dose - no surgical destruction of thyroid tissue
67
Why would thyroid drugs be combined with radio-iodine?
Thioamides maximize radio-iodine uptake due to decreased TH —> increased TSH —> increased radio-iodine uptake and decrease risk of thyroid storm
68
Benefits of radio-iodine
Cheap, safe, effective
69
Radio-iodine contraindications
Children Pregnancy Nursing
70
Radio-iodine side effects
Thyroiditis Salivary adenitis Inflammation at site of radiation
71
What is a partial thyroidectomy’s purpose?
Alternative to radio-iodine; typically for thyroid cancer, Grave’s disease Rare due to morbidity risk
72
Strategies before partial thyroidectomy
euthyroid 6 wk prior to surgery w/ thioamide Iodine therapy 2 wks before surgery Levo to treat hypothyroidism s/p surgery
73
Treatment of hyperthyroidism in young pt
MMI
74
Treatment of hyperthyroidism in old pt
Radio-iodine
75
Treatment of hyperthyroidism in pregnant pt
PTU
76
Treatment of hyperthyroidism in Grave’s disease
Surgery
77
Treatment of Thyroid Storm
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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