Chapter 22- Thyroid Flashcards
1
Q
What embryologic structure is the thyroid derived from?
A
1st and 2nd pharyngeal pouches
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
3
Q
Where is TSH released from? What are its effects?
A
Anterior pituitary gland; acts on thyroid to release T3 and T4
4
Q
How are TRH and TSH release regulated?
A
By T3 and T4 via negative feedback loop
5
Q
Where does the superior thyroid artery originate?
A
1st branch of external carotid
6
Q
What is the origin of the inferior thyroid artery?
A
Off thyrocervical trunk; supplies inferior and superior parathyroids
7
Q
Where should the inferior thyroid artery be ligated during thyroidectomy?
A
Close to thyroid to avoid injury to parathyroid glands
8
Q
What is the Ima artery?
A
Occurs in 1%, arises from innominate or aorta and goes to the isthmus
9
Q
Where do the superior and middle thyroid veins drain?
A
Internal jugular
10
Q
Where does the inferior thyroid vein drain?
A
Innominate vein
11
Q
How common are nonrecurrent laryngeal nerves?
A
2-3%, more common on right
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
13
Q
What does loss of superior laryngeal nerve cause?
A
Loss of projection and easy voice fatigability (opera singers)
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
15
Q
What does injury to the recurrent laryngeal nerve cause?
A
Hoarseness; bilateral injury can obstruct airway needing emergent trach
16
Q
Where is the ligament of Berry?
A
Posterior medial suspensory ligament close to RLNs; careful dissection
17
Q
That is thyroglobulin?
A
Stores T3/T4 in colloid
18
Q
What is the plasma T4:T3 ratio?
A
15:1
19
Q
Is T3 or T4 more biologically active?
A
T3; most produced in periphery by T4 to T3 conversion by peroxidases
20
Q
What enzyme links/separates tyrosine and iodine?
A
Peroxidase
21
Q
What is the most sensitive lab indicator of gland function?
A
TSH
22
Q
What does thyroid-binding globulin do?
A
Thyroid hormone transport; T3/T4 also binds albumin
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
24
Q
What do parafollicular C cells produce?
A
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
