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Chapter 22- Thyroid Flashcards

1
Q

What embryologic structure is the thyroid derived from?

A

1st and 2nd pharyngeal pouches

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2
Q

Where is thyrotropin-releasing factor released from? What does it act on?

A

Hypothalamus; acts on anterior pituitary gland and causes release of TSH

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3
Q

Where is TSH released from? What are its effects?

A

Anterior pituitary gland; acts on thyroid to release T3 and T4

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4
Q

How are TRH and TSH release regulated?

A

By T3 and T4 via negative feedback loop

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5
Q

Where does the superior thyroid artery originate?

A

1st branch of external carotid

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6
Q

What is the origin of the inferior thyroid artery?

A

Off thyrocervical trunk; supplies inferior and superior parathyroids

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7
Q

Where should the inferior thyroid artery be ligated during thyroidectomy?

A

Close to thyroid to avoid injury to parathyroid glands

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8
Q

What is the Ima artery?

A

Occurs in 1%, arises from innominate or aorta and goes to the isthmus

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9
Q

Where do the superior and middle thyroid veins drain?

A

Internal jugular

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10
Q

Where does the inferior thyroid vein drain?

A

Innominate vein

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11
Q

How common are nonrecurrent laryngeal nerves?

A

2-3%, more common on right

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12
Q

Where does the superior laryngeal nerve run? What does it supply?

A

Runs lateral to thyroid lobes, close to superior thyroid artery; motor to cricothyroid

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13
Q

What does loss of superior laryngeal nerve cause?

A

Loss of projection and easy voice fatigability (opera singers)

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14
Q

Where does the recurrent laryngeal nerve run? What does it supply?

A

Runs posterior to thyroid lobes in the tracheoesophageal groove, can track with inferior thyroid a., L. loops around aorta, R. loops around right sublclavian; provides motor to all of the larynx except cricothyroid

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15
Q

What does injury to the recurrent laryngeal nerve cause?

A

Hoarseness; bilateral injury can obstruct airway needing emergent trach

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16
Q

Where is the ligament of Berry?

A

Posterior medial suspensory ligament close to RLNs; careful dissection

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17
Q

That is thyroglobulin?

A

Stores T3/T4 in colloid

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18
Q

What is the plasma T4:T3 ratio?

A

15:1

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19
Q

Is T3 or T4 more biologically active?

A

T3; most produced in periphery by T4 to T3 conversion by peroxidases

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20
Q

What enzyme links/separates tyrosine and iodine?

A

Peroxidase

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21
Q

What is the most sensitive lab indicator of gland function?

A

TSH

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22
Q

What does thyroid-binding globulin do?

A

Thyroid hormone transport; T3/T4 also binds albumin

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23
Q

Where are the Tubercles of Zuckerkandl?

A

Most lateral, posterior extension of thyroid tissue; rotate medially to find RLNs; left behind in subtotal thyroidectomies

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24
Q

What do parafollicular C cells produce?

A

Calcitonin

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25
Q

What is the resin T3 uptake measure?

A

Mesures free T3 by having it bind resin; increased uptake = hyperthyroidism or low TBG; decreased uptake = hypothyroidism or high TBG

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26
Q

What should TSH levels do with thyroxine treatment?

A

Fall to 50%

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27
Q

What is a long-term side effect of thyroxine?

A

Osteoporosis

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28
Q

What is the treatment for postthyroidectomy stridor?

A

Open neck and remove hematoma; can result in airway compromise

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29
Q

Symptoms of thyroid storm?

A

Tachycardia, fever, numbness, irritability, vomiting, diarrhea, high output cardiac failure

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30
Q

Thyroid storm can be precipitated by what?

A

Post op in undiagnosed Grave’s disease, anxiety, excessive palpation of the gland, adrenergic stimulants

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31
Q

Treatment for thyroid storm?

A

Beta-blockers, PTU, Lugol’s solution (KI), cooling blankets, oxygen, glucose, fluid

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32
Q

What is the Wolff-Chaikoff effect?

A

High doses of iodine (Lugol’s solution), which inhibits TSH action on thyroid and inhibits organic coupling of iodide, resulting in less T3/T4

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33
Q

What is the 1st step in workup of asymptomatic thyroid nodule?

A

Thyroid function tests: if elevated, give thyroxine (nodule should regress within 6mo); if not elevated, proceed to FNA

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34
Q

2nd step in workup of asymptomatic thyroid nodule when TFTs are normal?

A

FNA (determinant in 75-90%)

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35
Q

Treatment when FNA shows follicular cells?

A

Thyroidectomy or lobectomy (5-10% malignancy risk)

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36
Q

Treatment when FNA shows thyroid CA?

A

Thyroidectomy or lobectomy

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37
Q

Treatment when FNA shows cyst fluid?

A

Drain fluid; if it recurs, thyroidectomy or lobectomy

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38
Q

Treatment when FNA shows colloid tissue

A

Most likely colloid goiter; low chance of malignancy (<1%); treatment: thyroxine, thyroidectomy or lobectomy if it enlarges

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39
Q

Next step in workup of asymptomatic thyroid nodule if FNA is indeterminant (10-25%)?

A

Radionuclide study

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40
Q

Treatment for hot nodule on radionuclide study?

A

Thyroxine for 6mo; if size does not go down, lobectomy

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41
Q

Treatment for cold nodule on radionuclide study?

A

Thyroidectomy or lobectomy (more likely malignant than hot nodule)

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42
Q

% of thyroid nodules that are benign?

A

85%

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43
Q

1 cause of goiter?

A

Iodine deficiency

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44
Q

Treatment for goiter?

A

Iodine replacement

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45
Q

Definition of nontoxic goiter?

A

Diffuse enlargement without evidence of functional abnormality

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46
Q

Treatment of nontoxic goiter?

A

Suppress with thyroxine; 131I, thioamides, subtotal thyroidectomy or lobectomy on side of goiter if medical treatment ineffective

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47
Q

What is a primary vs. secondary goiter?

A

Primary (rare): vessels originate from innominate artery; secondary: vessels originate from superior and inferior thyroid arteries

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48
Q

Where does mediastinal thyroid tissue come from?

A

Most likely from acquired disease with inferior extensions of a normally placed gland

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49
Q

% with pyramidal lobe?

A

10%; extends from isthmus toward the thymus

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50
Q

Where is a lingual thyroid found?

A

Thyroid tissue that persists in the are of the foramen cecum at the base of the tongue

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51
Q

Symptoms of lingual thyroid?

A

Dysphagia, dyspnea, dysphonia

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52
Q

% malignancy risk with lingual thyroid?

A

2%

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53
Q

Treatment of lingual thyroid?

A

Thyroxine suppression; abolish with 131I or resection if enlarged

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54
Q

Lungual thyroid is the only thyroid tissue in what % of patients that have it?

A

70%

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55
Q

Classic sign of thyroglossal duct cyst?

A

Moves upward with swallowing

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56
Q

Complications of thyroglossal duct cyst?

A

Can be premalignant, susceptible to infection

57
Q

Treatment for thyroglossal duct cyst?

A

Resection; need to take midportion or all of hyoid bone along with the thyroglossal duct cyst

58
Q

Use of propylthiouracil and methimazole?

A

Good for young patients, small goiters, mild T3/T4 elevation

59
Q

Mechanism of action of propylthiouracil?

A

Inhibits peroxidases and prevents DIT and MIT coupling

60
Q

Side effects of PTU?

A

Aplastic anemia, agranulocytosis

61
Q

MOA of methimazole?

A

Inhibits peroxidases and prevents DIT and MIT coupling

62
Q

Side effects of methimazole?

A

Cretinism in newborns (crosses the placenta), aplastic anemia or agranulocytosis

63
Q

When is radioactive iodine used?

A

In patients who are poor surgical risks or unresponsive to PTU

64
Q

When is the best time to perform thyroidectomy in pregnant patients?

A

2nd trimester; decreased risk of teratogenic events and premature labor

65
Q

Most common cause of hyperthyroidism?

A

Graves’ disease (80%)

66
Q

Signs of Graves’ disease?

A

More common in women; exophthalmos, pretibial edema, atrial fibrilation, heart dysfunction, heat intolerance, thirst, increased appetite, weight loss, sweating, palpitations

67
Q

Cause of Graves’ disease?

A

IgG antibodies to TSH receptor (long-activng thyroid stimulatory, thyroid-stimulating immunoglobulin)

68
Q

Diagnosis of graves’ disease?

A

Increased 123I uptake diffusely in thyrotoxic patient with goiter; LATS level, decreased TSH, increased T3/T4

69
Q

Treatment of Graves’ disease?

A

Thioamides (70% recurrenc), 131I (10% recurrence), subtotal thyroidectomy or total thyroidectomy with thyroxine replacement if medical therapy fails

70
Q

Preop preparation prior to thyroidectomy for Graves’ disease?

A

PTU or methimazole until euthyroid, beta-blocker, 1 week before surgery, Lugol’s solution 10-15d to decrease friability and vascularity

71
Q

Indications for surgery for Graves’ disease?

A

Noncompliant patient, recurrence after medical therapy, children, pregnant women not controlled with medical therapy, or concomitant suspicious thyroid nodule

72
Q

What is the most common cause of thyroid enlargement?

A

Toxic multinodular goiter

73
Q

TFTs seen in toxic multinodular goiter?

A

Normal

74
Q

Symptoms of toxic multinodular goiter?

A

Cardiac symptoms, weight loss, insomnia, airway compromise; symptoms can be precipitated by contrast dyes

75
Q

What is toxic mutinodular goiter caused by?

A

Hyperplasia secondary to chronic low-grade TSH stimulation

76
Q

Treatment of toxic multinodular goiter?

A

131I and thioamides; subtotal thyroidectomy if medical treatment ineffective

77
Q

Presentation of single toxic nodule?

A

Women; younger; can cause cervical compression

78
Q

Diagnosis of single toxic nodule?

A

Thyroid scan

79
Q

% of hot nodules that will cause symptoms?

A

20%

80
Q

Treatment of single toxic nodule?

A

131I and thioamides; lobectomy if medical treatment ineffective

81
Q

Most common cause of hypothyroidism in adults?

A

Hashimoto’s disease

82
Q

Cause of Hashimoto’s disease?

A

Humeral and cell-mediated autoimmune disease (microsomal and thyroglobulin antibodies)

83
Q

What is the goiter of Hashimoto’s disease caused by?

A

Secondary to lack of organification of trapped iodide inside gland

84
Q

Pathology of Hashimoto’s disease?

A

Lymphocytic infiltrate

85
Q

Treatment for Hashimoto’s disease?

A

1st line: thyroxine; partial thyroidectomy if continues to grow, if nodules appear, or compression symptoms occur

86
Q

What is the most common cause of bacterial thyroiditis?

A

Contiguous spread

87
Q

Signs/symptoms of bacterial thyroiditis?

A

Normal TFTs, fever, dysphagia, tenderness

88
Q

Treatment for bacterial thyroiditis?

A

Antibiotics; may need lobectomy to r/o cancer in pt with unilateral swelling and tenderness

89
Q

Signs/symptoms of DeQuervain’s thyroiditis?

A

Viral URI, tender thyroid, sore throat, mass, weakness, fatigue, elevated ESR

90
Q

DeQuervain’s thyroiditis is associated with hypo-, hyper-, or euthyroidism?

A

Hyperthyroidism

91
Q

Treatment for DeQuervain’s thyroiditis?

A

Steroids and ASA; may need lobectomy to r/o cancer in pts with unilateral swelling and tenderness

92
Q

What is Riedel’s fibrous struma?

A

Woody, fibrous component that can involve adjacent strap muscles and carotid sheath; can resemble thyroid CA or lymphoma (need biospy)

93
Q

Complications of Riedel’s fibrous struma?

A

Hypothyroidism and compression symptoms

94
Q

Conditions associated with Riedel’s fibrous struma?

A

Sclerosing cholangitis, fibrotic diseases, methysergide treatment, retroperitoneal fibrosis

95
Q

Treatment for Reidel’s fibrous struma?

A

Steroids and thyroxine; may need isthmectomy or tracheostomy

96
Q

What is the most common endocrine malignancy in the US?

A

Thyroid cancer

97
Q

Characteristics of tumor worrisome for malignancy?

A

Solid, solitary, cold, slow growing, hard; male, age >50, previous neck XRT, MEN IIa or IIb

98
Q

What does sudden growth of thyroid tumor imply?

A

Hemorrhage into previously undetected nodule or malignany

99
Q

How are thyroid adenomas differentiated from carcinomas?

A

Require lobectomy

100
Q

What is the cancer risk of follicular adenomas?

A

No increase in cancer risk; still need lobectomy to prove it is adenoma

101
Q

What is the most common thyroid carcinoma?

A

Papillary thyroid carcinoma (80-90%)

102
Q

Which thyroid cancer is the slowest growing, least aggressive, with the best prognosis?

A

Papillary thyroid carcinoma

103
Q

What is the most common tumor following neck XRT?

A

Papillary thyroid carcinoma

104
Q

What factor predicts a worse prognosis for papillary thyroid carcinoma?

A

Older age (>40-50y)

105
Q

Prognosis of papillary thyroid carcinoma is based on what?

A

Local invasion

106
Q

Papillary carcinoma mets most commonly go where?

A

Lung

107
Q

What does pathology of papillary carcinoma show?

A

Psammoma bodies (calcium) and Orphan Annie nuclei

108
Q

Treatment for <1cm papillary carcinoma?

A

Lobectomy

109
Q

What are the indications for total thyroidectomy with papillary carcinoma?

A

Bilateral, multicentricity, history of XRT, positive margins, tumors >1cm

110
Q

Treatment for clinically positive cervical nodes or extrathyroidal tissue involvement with papillary/follicular carcinoma?

A

Ipsilateral MRND

111
Q

Treatment for metastatic disease, residual local disease, positive lymph nodes or capsular invasion with papillary carcinoma?

A

131I 6 wks after surgery

112
Q

5 year survival with papillary carcinoma?

A

95%; death secondary to local disease

113
Q

How does follicular thyroid carcinoma spread?

A

Hematogenous spread (to bone most common)

114
Q

What % of follicular carcinoma is metastatic at time of presentation?

A

50%

115
Q

WWhat does FNA show with follicular carcinoma?

A

Follicular cells; 10% chance of malignancy, need thyroidectomy

116
Q

Treatment for adenoma or follicular cell hyperplasia?

A

Lobectomy

117
Q

Treatment for follicular carcinoma >1cm or extrathyroidal?

A

Total thyroidectomy

118
Q

Treatment for follicular carcinoma >1cm or extrathyroidal disease?

A

131I 6 wks after surgery

119
Q

5 year survival for follicular carcinoma?

A

70%; prognosis based on stage

120
Q

Syndrome associated with medullary thyroid carcinoma?

A

MEN IIa and IIb

121
Q

What cells do medullary thyroid carcinoma arise from?

A

Parafollicular C cells; C-cell hyperplasia considered premalignant

122
Q

Pathology of medullary carcinoma shows what?

A

Amyloid deposition

123
Q

What test can be used to look for medullary thyroid carcinoma?

A

Gastrin; caused an increase in calcitonin

124
Q

What do you need to screen for when a patient has been diagnosed with medullary carcinoma?

A

Hyperparathyroidism and pheochromocytoma

125
Q

Where does follicular carcinoma mets go?

A

Lung, liver, bone

126
Q

Treatment for medullary carcinoma?

A

Total thyroidectomy with central neck node dissection

127
Q

When is MRND indicated with medullary carcinoma?

A

Clinically positive nodes (bilateral MRND if tumor on both sides of thyroid), or with extrathyroidal disease

128
Q

Treatment for MEN IIa or IIb?

A

Prophylactic thyroidectomy and central node dissection at age 2

129
Q

5 year survival with medullary carcinoma?

A

50%; prognosis based on presence of regional and distant mets

130
Q

Hurthle cell mets go where?

A

Early nodal spread if malignant, bone and lung

131
Q

Treatment for Hurthle cell carcinoma?

A

Total thyroidectomy; MRND for clinically positive nodes

132
Q

Characteristics of patients with anaplastic thyroid cancer?

A

Elderly patients with long-standing goiter

133
Q

5 year survival for anaplastic thyroid cancer?

A

0%; usually beyond surgical management by diagnosis

134
Q

Treatment for anaplastic thyroid cancer?

A

Total thyroidectomy for rare resectable lesion; palliative thyroidectomy for compressive symptoms, palliative chemo/XRT

135
Q

What carcinomas is XRT effective for?

A

Papillary, follicular, medullary, Hurthle cell

136
Q

What carcinomas is 131I effective for?

A

Papillary and follicular thyroid cancer only

137
Q

Side effects of 131I?

A

Sialoadenitis, GI symptoms, infertility, bone marrow suppression, parathyroid dysfunction, leukemia

138
Q

When is the best time to 131I scan for mets?

A

4-6 weeks after thyroidectomy when TSH levels are highest

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