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Z.Fiser > Fiser.22.Thyroid > Flashcards

Fiser.22.Thyroid Flashcards

1
Q

what is the embryologic origin of the thyroid gland?

A

1st and 2nd pharyngeal arches (not pouches)

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2
Q

where is TRF released from and what does it do?

A

thyrotropin releasing factor is released from the hypothalamus, acts on anterior pituitary gland to cause release of TSH

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3
Q

where is TSH released from and what does it do?

A

released from anterior pituiatary gland, acts on thyroid gland to release T3 and T4

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4
Q

what is the mediator that causes TSH to act on the thyroid gland?

A

elevated cAMP allows TSH to cause thyroid to release T3/T4

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5
Q

what controls TRH/TSH release through negative feedback?

A

T3 & T4

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6
Q

where does superior thyroid artery branch off of?

A

1st branch off external carotid artery

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7
Q

where does the inferior thyroid artery branch off of?

A

off thyrocervical trunk

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8
Q

what is the blood supply to the superior parathyroids?

A

inferior thyroid artery

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9
Q

what is the blood supply to the inferior parathyroids?

A

inferior thyroid artery

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10
Q

what surgical maneuver do you perform during thyroidectomy to avoid injury to the parathyroid glands?

A

ligate the inferior thyroid artery close to the thyroid gland to avoid injury to the parathyroid glands

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11
Q

what is the incidence of the ima artery?

A

1%

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12
Q

where does the ima artery branch from and what does it supply?

A

branches from the innominate or aorta and goes to the isthimus

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13
Q

where does the superior thyroid vein drain?

A

into the IJV

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14
Q

where does the middle thyroid vein drain?

A

into the IJV

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15
Q

where does the inferior thyroid vein drain?

A

into the innominate vein

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16
Q

where does the superior laryngeal nerve run?

A

lateral to thyroid lobes, close to the superior thyroid artery

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17
Q

what are the vocal effects of injury to the superior laryngeal nerve?

A

loss of projection and easy voice fatigability

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18
Q

what muscle does the superior laryngeal nerve supply?

A

motor to the cricothyroid muscle

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19
Q

what muscles do the recurrent laryngeal nerves supply?

A

motor to all of larynx except cricothyroid muscle

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20
Q

what are the tracks of the recurrent laryngeal nerve

A

run posterior to thyroid lobes in the tracheoesophageal groove, can qqf track with the inferior thyroid artery, left RLN loops around aorta, right RLN loops around innominate artery

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21
Q

what is the result of unilateral recurrent laryngeal nerve injury?

A

hoarseness

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22
Q

what is the result of bilateral recurrent laryngeal nerve injury and how is it managed?

A

can obstruct airway, tx with emergent tracheostomy

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23
Q

what is the frequency of non-recurrent laryngeal nerve and what is its MC laterality?

A

in 2% of the population, MC on the right

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24
Q

is the risk of injury higher for recurrent laryngeal nerve or its non-recurrent variant during thyroid surgery?

A

the non-recurrent laryngeal nerve variant is at higher risk for injury during thyroid surgery

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25
Q

where is the ligament of Berry located and what is its function

A

posterior medial suspensory ligament close to the recurrent laryngeal nerves

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26
Q

how does the Ligament of Berry affect thyroid surgery

A

requires careful dissection

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27
Q

what is the function of thyroglobulin?

A

stores T3 and T4 in colloid

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28
Q

what is a normal T4:T3 ratio in serum?

A

15:1

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29
Q

what is the more active form of thyroid horomone, T3 or T4 and why?

A

T3 b/c it is tyrosine + iodine

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30
Q

how is T3 produced?

A

T4 –> T3 conversion in serum in the periphery, conversion by deiodinases

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31
Q

what is the function of thyroid peroxidase

A

link iodine and tyrosine together

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32
Q

what is the function of thyroid deiodinases

A

separate iodine from tyrosine

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33
Q

what is the function of thyroid-binding globulin?

A

thyroid hormone transport; binds the majority of T3/T4 in circulation

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34
Q

what serum marker is the most sensitive indicator of thyroid gland function

A

TSH

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35
Q

what and where are the tubercles of zuckerkandl located?

A

most lateral and posterior extension of thyroid tissue

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36
Q

how are tubercles of zuckerkandl manipulated during total and subtotal thyroidectomy?

A

rotate medially to find recurrent laryngeal nerves. Left behind with subtotal thyroidectomy because of proximity to RLNs

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37
Q

what is the function of parafollicular C-cells in the thyroid?

A

produce calcitonin

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38
Q

what is the expected effect of thyroxine treatment on TSH levels?

A

TSH levels should fall by 50%

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39
Q

name a long-term side effect of thyroxine

A

osteoporosis

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40
Q

how do you manage post-thyroidectomy stridor

A

open neck, remove hematoma / if 2/2 bilateral RLN injury needs emergent trach

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41
Q

what are the S/Sx of thyroid storm (7)

A

tachycardia, fever, numbness, irritability, vomiting, diarrhea, high-output cardiac failure

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42
Q

what is the MCC of death 2/2 thyroid storm?

A

high-output cardiac failure

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43
Q

what is the MCC of thyroid storm in the postop pt?

A

undiagnosed Grave’s disease

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44
Q

name three causes of thyroid storm in the postop pt

A

anxiety, excessive gland palpation, adrenergic stimulants

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45
Q

how do you treat thyroid storm?

A

beta-blockers (first line); PTU, Lugol’s solution, cooling blankets, oxygen, glucose

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46
Q

when is thyroid storm surgery indicated?

A

emergent thyroidectomy is rarely indicated

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47
Q

What is the Wolff-Chaikoff effect and how is it related to thyroid storm?

A

pt given high doses of iodine (Lugol’s solution, potassium iodide), which inhibits TSH action on the thyroid and inhibits organic coupling of iodide, resulting in less T3 and T4 release

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48
Q

what percent of thyroid nodules are benign?

A

90%

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49
Q

what is the gender predominance for asymptomatic thyroid nodules

A

females

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50
Q

what are the two initial tests to evaluate an asymptomatic thyroid nodule?

A

FNA and thyroid function tests

51
Q

what is the management of an asymptomatic thyroid nodule with follicular cells on FNA and why?

A

lobectomy due to 10% cancer risk

52
Q

what is the management of an asymptomatic thyroid nodule with cancerous cells on FNA?

A

total thyroidectomy or lobectomy, depending on subtype of cancer

53
Q

what is the management of an asymptomatic thyroid nodule with cyst fluid on FNA?

A

drain fluid

54
Q

what is the management of an asymptomatic thyroid nodule with cyst fluid on FNA and bloody fluid on aspiration?

A

lobectomy

55
Q

what is the management of an asymptomatic thyroid nodule with cyst fluid on FNA that recurs after drainage?

A

lobectomy

56
Q

what is the dx and management of an asymptomatic thyroid nodule with colloid on FNA?

A

most likely colloid goiter, tx with thyroxine, lobectomy if enlarges

57
Q

what is the chance of malignant transformation with colloid goiter

A

<1% chance of malignancy

58
Q

what is the diagnosis of an asymptomatic thyroid nodule with FNA showing normal thyroid tissue and elevated thyroid function tests?

A

solitary toxic nodule

59
Q

what is the management of an asymptomatic thyroid nodule with FNA showing normal thyroid tissue and elevated thyroid function tests?

A

solitary toxic nodule, just monitor if asx

60
Q

what is the management of a SYMPTOMATIC thyroid nodule with FNA showing normal thyroid tissue and elevated thyroid function tests?

A

PTU and iodine-131 if symptomatic

61
Q

what is the next step in diagnosis for evaluation of an asymptomatic thyroid nodule with normal findings on FNA and thyroid function tests?

A

get radionuclide study

62
Q

what is the treatment of an asymptomatic vs symptomatic thyroid nodule with normal findings on FNA and TFTs and hot nodule findings on radionuclide study?

A

if asymptomatic can monitor; if symptomatic PTU and iodine 131

63
Q

what is the treatment of an asymptomatic thyroid nodule with normal findings on FNA and TFTs and cold nodule findings on radionuclide study? why is this different from a hot nodule?

A

treat cold nodule with lobectomy, more likely to be malignant than hot nodule

64
Q

what is a goiter

A

any abnormal enlargement of the thyroid gland

65
Q

what is the most identifiable cause of goiter and its treatment?

A

most identifiable cause = iodine deficiency. Treatment = iodine supplementation

66
Q

what is the diagnosis for a diffuse thyroid enlargement without evidence of functioning abnormality

A

nontoxic colloid goiter

67
Q

what are two indications to operate on a goiter?

A

if its causing airway compromise or if there is a suspicious nodule - treat with a subtotal or total thyroidectomy

68
Q

what is the advantage of a subtotal over total thyroidectomy in treatment of goiter?

A

subtotal has decreased risk of RLN injury

69
Q

what is the MCC of substernal goiter?

A

usually secondary, since vessels originate from superior and inferior thyroid arteries

70
Q

what is the blood supply for a primary substernal goiter and how common is it?

A

its rare, vessels originate from the innominate artery

71
Q

what is the frequency of the pyramidal lobe of the thyroid and where is it located?

A

10%; extends from isthmus towards the thymus

72
Q

what is the underlying pathophysiology/embryology of lingual thyroid?

A

thyroid tissue that persists in the foramen cecum at the base of the tongue

73
Q

what are the sx a/w lingual thyroid (3)

A

dysphagia, dyspnea, dysphonia

74
Q

what is the malignancy risk a/w lingual thyroid?

A

2% malignancy risk

75
Q

what is the first- and second-line treatment for lingual thyroid?

A

first-line: thyroxine suppression & abolish with iodine-131; second-line: resection if it doesn’t shrink after therapy or concern for malignancy

76
Q

what percent of patients with lingual thyroid is that tissue the ONLY thyroid tissue they have?

A

70%

77
Q

PHOTO what is the classical physical exam findings with thyroglossal duct cysts?

A

moves upward with swallowing

78
Q

what are two complications of thyroglossal duct cysts?

A

susceptible to infection and may be premalignant

79
Q

PHOTO what is the treatment of thyroglossal duct cyst?

A

resection –> Sistrunk procedure (take midportion / all of hyoid bone along with the thyroglossal duct cyst)

80
Q

what are the advantages of using PTU and/or methimazole for treatment of hyperthyroidism? (3)

A

good for young patients; small goiters, and mild T3/T4 elevation

81
Q

which antihyperthyroid treatment is safe in pregnancy: propylthiouracil or methimazole?

A

PTU is safe in pregnancy, methimazole crosses the placenta

82
Q

what is the MOA of PTU?

A

inhibits peroxidases and prevents iodine-tyrosine coupling

83
Q

what are two side effects of PTU?

A

aplastic anemia, agranulocytosis

84
Q

what is the class of drugs PTU belongs to?

A

propylthiouracil is a thioamide

85
Q

what is the MOA of methimazole?

A

inhibits peroxidases and prevents iodine-typrosine coupliing

86
Q

what are three AEs of methimazole?

A

cretinism in newborns (crosses placenta); aplastic anemia; agranulocytosis

87
Q

when is radioactive iodine (I-131) a good option to treat hyperthyroidism?

A

good for patients who are poor surgical risk candidates or are unresponsive to PTU

88
Q

what two patient populations should NOT be treated with radioactive iodine (I-131)?

A

children or during pregnancy (can traverse the placenta)

89
Q

name five indications for thyroidectomy when treating hyperthyroidism

A

cold nodules; toxic adenomas / multinodular goiters not responsive to medical therapy; pregnant patients not controlled with PTU; compressive symptoms

90
Q

when is the best time to perform a thyroidectomy on a hyperthyroid pregnant patient and two reasons why

A

best time to operate is during the second trimester b/c reduced risk of teratogenic effect and premature labor

91
Q

what are the potential effects of performing a subtotal thyroidectomy on a hyperthyroid patient?

A

can become euthyroid

92
Q

what is another name for Grave’s disease?

A

toxic diffuse goiter

93
Q

which sex has a predisposition to Grave’s disease?

A

women

94
Q

name 8 S/Sx a/w Grave’s disase

A

exopthalmos, pretibial edema, Afib, heat intolerance, thirst, increased appetite, weight loss, sweating, palpitations

95
Q

what percent of cases of hyperthyroidism are 2/2 Grave’s disease?

A

80%

96
Q

what is the MCC of hyperthyroidism?

A

Grave’s disease

97
Q

what is the underlying pathophysiology of Grave’s disease

A

IgG antibodies to the TSH resceptor (long-acting thyroid stimulator / thyroid-stimulating immunoglobulin)

98
Q

how do you diagnose Grave’s disease?

A

decreased TSH, increased T3/T4, increased LATS level (long-acting thyroid stimulator); diffusely increased Iodine-123 uptake (thyroid scan)

99
Q

what are the first, second, and third-line therapies for Grave’s disease?

A

first-line: thioamides; second-line: radioactive iodine 131; third-line: thyroidectomy if medical therapy fails

100
Q

what is the rate of recurrence of Grave’s disease treated with thioamides?

A

50% recurrence

101
Q

what is the recurrence rate of Grave’s disease treated with radioactive iodine 131?

A

5%

102
Q

what is the rate of recurrence of Grave’s disease after bilateral subtotal thyroidectomy?

A

5%

103
Q

what is the MC reason to need to operate on a patient with Grave’s disease?

A

suspicious nodule

104
Q

what is the preop preparation required prior to surgical treatment of Grave’s disease?

A

PTU until euthyroid. Once euthyroid –> beta blocker, Lugol’s solution x 14 days to decrease friability and vascularity

105
Q

what are the two operative procedures to treat Grave’s disease?

A

bilateral subtotal thyroidectomy or total thyroidectomy

106
Q

what do Grave’s disease patients require s/p total thyroidectomy?

A

lifetime thyroxine replacement

107
Q

name the five indications for thyroid surgery in Grave’s disease. What is the MCC?

A

MCC = suspicious thyroid nodule. Others are noncompliant patient, recurrence after medical therapy, children, pregnant women not controlled with PTU

108
Q

what age and sex does toxic multinodular goiter tend to present in?

A

women over age 50

109
Q

name four S/Sx of toxic multinodular goiter

A

tachycardia, weight loss, insomnia, airway compromise

110
Q

what exogenous substance can trigger the S/Sx of toxic multinodular goiter?

A

contrast dyes

111
Q

what is the underlying pathophysiology of toxic multinodular goiter

A

thyroid hyperplasia secondary to chronic low-grade TSH stimulation

112
Q

what is the preferred initial treatment for toxic multinodular goiter?

A

surgery: subtotal or total thyroidectomy

113
Q

what treatment of toxic multinodular goiter should be considered before surgery? in what patient population in particular?

A

consider a trial of iodine 131 (radioactive), especially inthe elderly and rfrail

114
Q

what are two indications for surgery over radioactive iodine to treat toxic multinodular goiter

A

if airway compression or a suspicious nodule are present

115
Q

what age and sex do single toxic thyroid nodules present?

A

in younger women

116
Q

what size to single toxic thyroid nodules need to be to produce symptoms?

A

> 3cm

117
Q

what is the underlying pathophysiology of single toxic thyroid nodules

A

function autonomously

118
Q

how do you diagnose a single toxic thyroid nodule?

A

thyroid scan will show a hot nodule

119
Q

what percentage of hot thyroid nodules eventually cause symptoms?

A

20% of thyroid nodules eventually cause symptoms

120
Q

what are the first and second-line treatments for single toxic thyroid nodules

A

thioamides and iodine 131 first line (95% effective); lobectomy if medical therapy ineffective

121
Q

name two rare causes of hyperthyroidism

A

trophoblastic tumors; TSH-secreting pituitary tumors

122
Q

what is the MCC of hypothyroidism in adults?

A

Hashimoto’s thyroiditis

123
Q

what are the physical exam findings in Hashimoto’s thyroiditis?

A

enlarged gland, painless, chronic thyroiditis

124
Q

what are the pathologic findings of Hashimoto’s thyroiditis

A

thyroid tissue has a lymphocytic infiltrate

Z.Fiser (22 decks)

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