Chapter 22- Thyroid Flashcards Preview

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Flashcards in Chapter 22- Thyroid Deck (138):
1

What embryologic structure is the thyroid derived from?

1st and 2nd pharyngeal pouches

2

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

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

3

Where is TSH released from? What are its effects?

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

4

How are TRH and TSH release regulated?

By T3 and T4 via negative feedback loop

5

Where does the superior thyroid artery originate?

1st branch of external carotid

6

What is the origin of the inferior thyroid artery?

Off thyrocervical trunk; supplies inferior and superior parathyroids

7

Where should the inferior thyroid artery be ligated during thyroidectomy?

Close to thyroid to avoid injury to parathyroid glands

8

What is the Ima artery?

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

9

Where do the superior and middle thyroid veins drain?

Internal jugular

10

Where does the inferior thyroid vein drain?

Innominate vein

11

How common are nonrecurrent laryngeal nerves?

2-3%, more common on right

12

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

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

13

What does loss of superior laryngeal nerve cause?

Loss of projection and easy voice fatigability (opera singers)

14

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

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

15

What does injury to the recurrent laryngeal nerve cause?

Hoarseness; bilateral injury can obstruct airway needing emergent trach

16

Where is the ligament of Berry?

Posterior medial suspensory ligament close to RLNs; careful dissection

17

That is thyroglobulin?

Stores T3/T4 in colloid

18

What is the plasma T4:T3 ratio?

15:1

19

Is T3 or T4 more biologically active?

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

20

What enzyme links/separates tyrosine and iodine?

Peroxidase

21

What is the most sensitive lab indicator of gland function?

TSH

22

What does thyroid-binding globulin do?

Thyroid hormone transport; T3/T4 also binds albumin

23

Where are the Tubercles of Zuckerkandl?

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

24

What do parafollicular C cells produce?

Calcitonin

25

What is the resin T3 uptake measure?

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

26

What should TSH levels do with thyroxine treatment?

Fall to 50%

27

What is a long-term side effect of thyroxine?

Osteoporosis

28

What is the treatment for postthyroidectomy stridor?

Open neck and remove hematoma; can result in airway compromise

29

Symptoms of thyroid storm?

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

30

Thyroid storm can be precipitated by what?

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

31

Treatment for thyroid storm?

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

32

What is the Wolff-Chaikoff effect?

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

33

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

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

34

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

FNA (determinant in 75-90%)

35

Treatment when FNA shows follicular cells?

Thyroidectomy or lobectomy (5-10% malignancy risk)

36

Treatment when FNA shows thyroid CA?

Thyroidectomy or lobectomy

37

Treatment when FNA shows cyst fluid?

Drain fluid; if it recurs, thyroidectomy or lobectomy

38

Treatment when FNA shows colloid tissue

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

39

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

Radionuclide study

40

Treatment for hot nodule on radionuclide study?

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

41

Treatment for cold nodule on radionuclide study?

Thyroidectomy or lobectomy (more likely malignant than hot nodule)

42

% of thyroid nodules that are benign?

85%

43

#1 cause of goiter?

Iodine deficiency

44

Treatment for goiter?

Iodine replacement

45

Definition of nontoxic goiter?

Diffuse enlargement without evidence of functional abnormality

46

Treatment of nontoxic goiter?

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

47

What is a primary vs. secondary goiter?

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

48

Where does mediastinal thyroid tissue come from?

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

49

% with pyramidal lobe?

10%; extends from isthmus toward the thymus

50

Where is a lingual thyroid found?

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

51

Symptoms of lingual thyroid?

Dysphagia, dyspnea, dysphonia

52

% malignancy risk with lingual thyroid?

2%

53

Treatment of lingual thyroid?

Thyroxine suppression; abolish with 131I or resection if enlarged

54

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

70%

55

Classic sign of thyroglossal duct cyst?

Moves upward with swallowing

56

Complications of thyroglossal duct cyst?

Can be premalignant, susceptible to infection

57

Treatment for thyroglossal duct cyst?

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

58

Use of propylthiouracil and methimazole?

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

59

Mechanism of action of propylthiouracil?

Inhibits peroxidases and prevents DIT and MIT coupling

60

Side effects of PTU?

Aplastic anemia, agranulocytosis

61

MOA of methimazole?

Inhibits peroxidases and prevents DIT and MIT coupling

62

Side effects of methimazole?

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

63

When is radioactive iodine used?

In patients who are poor surgical risks or unresponsive to PTU

64

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

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

65

Most common cause of hyperthyroidism?

Graves' disease (80%)

66

Signs of Graves' disease?

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

67

Cause of Graves' disease?

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

68

Diagnosis of graves' disease?

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

69

Treatment of Graves' disease?

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

70

Preop preparation prior to thyroidectomy for Graves' disease?

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

71

Indications for surgery for Graves' disease?

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

72

What is the most common cause of thyroid enlargement?

Toxic multinodular goiter

73

TFTs seen in toxic multinodular goiter?

Normal

74

Symptoms of toxic multinodular goiter?

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

75

What is toxic mutinodular goiter caused by?

Hyperplasia secondary to chronic low-grade TSH stimulation

76

Treatment of toxic multinodular goiter?

131I and thioamides; subtotal thyroidectomy if medical treatment ineffective

77

Presentation of single toxic nodule?

Women; younger; can cause cervical compression

78

Diagnosis of single toxic nodule?

Thyroid scan

79

% of hot nodules that will cause symptoms?

20%

80

Treatment of single toxic nodule?

131I and thioamides; lobectomy if medical treatment ineffective

81

Most common cause of hypothyroidism in adults?

Hashimoto's disease

82

Cause of Hashimoto's disease?

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

83

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

Secondary to lack of organification of trapped iodide inside gland

84

Pathology of Hashimoto's disease?

Lymphocytic infiltrate

85

Treatment for Hashimoto's disease?

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

86

What is the most common cause of bacterial thyroiditis?

Contiguous spread

87

Signs/symptoms of bacterial thyroiditis?

Normal TFTs, fever, dysphagia, tenderness

88

Treatment for bacterial thyroiditis?

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

89

Signs/symptoms of DeQuervain's thyroiditis?

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

90

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

Hyperthyroidism

91

Treatment for DeQuervain's thyroiditis?

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

92

What is Riedel's fibrous struma?

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

93

Complications of Riedel's fibrous struma?

Hypothyroidism and compression symptoms

94

Conditions associated with Riedel's fibrous struma?

Sclerosing cholangitis, fibrotic diseases, methysergide treatment, retroperitoneal fibrosis

95

Treatment for Reidel's fibrous struma?

Steroids and thyroxine; may need isthmectomy or tracheostomy

96

What is the most common endocrine malignancy in the US?

Thyroid cancer

97

Characteristics of tumor worrisome for malignancy?

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

98

What does sudden growth of thyroid tumor imply?

Hemorrhage into previously undetected nodule or malignany

99

How are thyroid adenomas differentiated from carcinomas?

Require lobectomy

100

What is the cancer risk of follicular adenomas?

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

101

What is the most common thyroid carcinoma?

Papillary thyroid carcinoma (80-90%)

102

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

Papillary thyroid carcinoma

103

What is the most common tumor following neck XRT?

Papillary thyroid carcinoma

104

What factor predicts a worse prognosis for papillary thyroid carcinoma?

Older age (>40-50y)

105

Prognosis of papillary thyroid carcinoma is based on what?

Local invasion

106

Papillary carcinoma mets most commonly go where?

Lung

107

What does pathology of papillary carcinoma show?

Psammoma bodies (calcium) and Orphan Annie nuclei

108

Treatment for <1cm papillary carcinoma?

Lobectomy

109

What are the indications for total thyroidectomy with papillary carcinoma?

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

110

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

Ipsilateral MRND

111

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

131I 6 wks after surgery

112

5 year survival with papillary carcinoma?

95%; death secondary to local disease

113

How does follicular thyroid carcinoma spread?

Hematogenous spread (to bone most common)

114

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

50%

115

WWhat does FNA show with follicular carcinoma?

Follicular cells; 10% chance of malignancy, need thyroidectomy

116

Treatment for adenoma or follicular cell hyperplasia?

Lobectomy

117

Treatment for follicular carcinoma >1cm or extrathyroidal?

Total thyroidectomy

118

Treatment for follicular carcinoma >1cm or extrathyroidal disease?

131I 6 wks after surgery

119

5 year survival for follicular carcinoma?

70%; prognosis based on stage

120

Syndrome associated with medullary thyroid carcinoma?

MEN IIa and IIb

121

What cells do medullary thyroid carcinoma arise from?

Parafollicular C cells; C-cell hyperplasia considered premalignant

122

Pathology of medullary carcinoma shows what?

Amyloid deposition

123

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

Gastrin; caused an increase in calcitonin

124

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

Hyperparathyroidism and pheochromocytoma

125

Where does follicular carcinoma mets go?

Lung, liver, bone

126

Treatment for medullary carcinoma?

Total thyroidectomy with central neck node dissection

127

When is MRND indicated with medullary carcinoma?

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

128

Treatment for MEN IIa or IIb?

Prophylactic thyroidectomy and central node dissection at age 2

129

5 year survival with medullary carcinoma?

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

130

Hurthle cell mets go where?

Early nodal spread if malignant, bone and lung

131

Treatment for Hurthle cell carcinoma?

Total thyroidectomy; MRND for clinically positive nodes

132

Characteristics of patients with anaplastic thyroid cancer?

Elderly patients with long-standing goiter

133

5 year survival for anaplastic thyroid cancer?

0%; usually beyond surgical management by diagnosis

134

Treatment for anaplastic thyroid cancer?

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

135

What carcinomas is XRT effective for?

Papillary, follicular, medullary, Hurthle cell

136

What carcinomas is 131I effective for?

Papillary and follicular thyroid cancer only

137

Side effects of 131I?

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

138

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

4-6 weeks after thyroidectomy when TSH levels are highest