Fiser.22.Thyroid Flashcards
1
Q
what is the embryologic origin of the thyroid gland?
A
1st and 2nd pharyngeal arches (not pouches)
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
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
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
5
Q
what controls TRH/TSH release through negative feedback?
A
T3 & T4
6
Q
where does superior thyroid artery branch off of?
A
1st branch off external carotid artery
7
Q
where does the inferior thyroid artery branch off of?
A
off thyrocervical trunk
8
Q
what is the blood supply to the superior parathyroids?
A
inferior thyroid artery
9
Q
what is the blood supply to the inferior parathyroids?
A
inferior thyroid artery
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
11
Q
what is the incidence of the ima artery?
A
1%
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
13
Q
where does the superior thyroid vein drain?
A
into the IJV
14
Q
where does the middle thyroid vein drain?
A
into the IJV
15
Q
where does the inferior thyroid vein drain?
A
into the innominate vein
16
Q
where does the superior laryngeal nerve run?
A
lateral to thyroid lobes, close to the superior thyroid artery
17
Q
what are the vocal effects of injury to the superior laryngeal nerve?
A
loss of projection and easy voice fatigability
18
Q
what muscle does the superior laryngeal nerve supply?
A
motor to the cricothyroid muscle
19
Q
what muscles do the recurrent laryngeal nerves supply?
A
motor to all of larynx except cricothyroid muscle
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
21
Q
what is the result of unilateral recurrent laryngeal nerve injury?
A
hoarseness
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
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
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
25
where is the ligament of Berry located and what is its function
posterior medial suspensory ligament close to the recurrent laryngeal nerves
26
how does the Ligament of Berry affect thyroid surgery
requires careful dissection
27
what is the function of thyroglobulin?
stores T3 and T4 in colloid
28
what is a normal T4:T3 ratio in serum?
15:1
29
what is the more active form of thyroid horomone, T3 or T4 and why?
T3 b/c it is tyrosine + iodine
30
how is T3 produced?
T4 --> T3 conversion in serum in the periphery, conversion by deiodinases
31
what is the function of thyroid peroxidase
link iodine and tyrosine together
32
what is the function of thyroid deiodinases
separate iodine from tyrosine
33
what is the function of thyroid-binding globulin?
thyroid hormone transport; binds the majority of T3/T4 in circulation
34
what serum marker is the most sensitive indicator of thyroid gland function
TSH
35
what and where are the tubercles of zuckerkandl located?
most lateral and posterior extension of thyroid tissue
36
how are tubercles of zuckerkandl manipulated during total and subtotal thyroidectomy?
rotate medially to find recurrent laryngeal nerves. Left behind with subtotal thyroidectomy because of proximity to RLNs
37
what is the function of parafollicular C-cells in the thyroid?
produce calcitonin
38
what is the expected effect of thyroxine treatment on TSH levels?
TSH levels should fall by 50%
39
name a long-term side effect of thyroxine
osteoporosis
40
how do you manage post-thyroidectomy stridor
open neck, remove hematoma / if 2/2 bilateral RLN injury needs emergent trach
41
what are the S/Sx of thyroid storm (7)
tachycardia, fever, numbness, irritability, vomiting, diarrhea, high-output cardiac failure
42
what is the MCC of death 2/2 thyroid storm?
high-output cardiac failure
43
what is the MCC of thyroid storm in the postop pt?
undiagnosed Grave's disease
44
name three causes of thyroid storm in the postop pt
anxiety, excessive gland palpation, adrenergic stimulants
45
how do you treat thyroid storm?
beta-blockers (first line); PTU, Lugol's solution, cooling blankets, oxygen, glucose
46
when is thyroid storm surgery indicated?
emergent thyroidectomy is rarely indicated
47
What is the Wolff-Chaikoff effect and how is it related to thyroid storm?
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
48
what percent of thyroid nodules are benign?
90%
49
what is the gender predominance for asymptomatic thyroid nodules
females
50
what are the two initial tests to evaluate an asymptomatic thyroid nodule?
FNA and thyroid function tests
51
what is the management of an asymptomatic thyroid nodule with follicular cells on FNA and why?
lobectomy due to 10% cancer risk
52
what is the management of an asymptomatic thyroid nodule with cancerous cells on FNA?
total thyroidectomy or lobectomy, depending on subtype of cancer
53
what is the management of an asymptomatic thyroid nodule with cyst fluid on FNA?
drain fluid
54
what is the management of an asymptomatic thyroid nodule with cyst fluid on FNA and bloody fluid on aspiration?
lobectomy
55
what is the management of an asymptomatic thyroid nodule with cyst fluid on FNA that recurs after drainage?
lobectomy
56
what is the dx and management of an asymptomatic thyroid nodule with colloid on FNA?
most likely colloid goiter, tx with thyroxine, lobectomy if enlarges
57
what is the chance of malignant transformation with colloid goiter
<1% chance of malignancy
58
what is the diagnosis of an asymptomatic thyroid nodule with FNA showing normal thyroid tissue and elevated thyroid function tests?
solitary toxic nodule
59
what is the management of an asymptomatic thyroid nodule with FNA showing normal thyroid tissue and elevated thyroid function tests?
solitary toxic nodule, just monitor if asx
60
what is the management of a SYMPTOMATIC thyroid nodule with FNA showing normal thyroid tissue and elevated thyroid function tests?
PTU and iodine-131 if symptomatic
61
what is the next step in diagnosis for evaluation of an asymptomatic thyroid nodule with normal findings on FNA and thyroid function tests?
get radionuclide study
62
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?
if asymptomatic can monitor; if symptomatic PTU and iodine 131
63
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?
treat cold nodule with lobectomy, more likely to be malignant than hot nodule
64
what is a goiter
any abnormal enlargement of the thyroid gland
65
what is the most identifiable cause of goiter and its treatment?
most identifiable cause = iodine deficiency. Treatment = iodine supplementation
66
what is the diagnosis for a diffuse thyroid enlargement without evidence of functioning abnormality
nontoxic colloid goiter
67
what are two indications to operate on a goiter?
if its causing airway compromise or if there is a suspicious nodule - treat with a subtotal or total thyroidectomy
68
what is the advantage of a subtotal over total thyroidectomy in treatment of goiter?
subtotal has decreased risk of RLN injury
69
what is the MCC of substernal goiter?
usually secondary, since vessels originate from superior and inferior thyroid arteries
70
what is the blood supply for a primary substernal goiter and how common is it?
its rare, vessels originate from the innominate artery
71
what is the frequency of the pyramidal lobe of the thyroid and where is it located?
10%; extends from isthmus towards the thymus
72
what is the underlying pathophysiology/embryology of lingual thyroid?
thyroid tissue that persists in the foramen cecum at the base of the tongue
73
what are the sx a/w lingual thyroid (3)
dysphagia, dyspnea, dysphonia
74
what is the malignancy risk a/w lingual thyroid?
2% malignancy risk
75
what is the first- and second-line treatment for lingual thyroid?
first-line: thyroxine suppression & abolish with iodine-131; second-line: resection if it doesn't shrink after therapy or concern for malignancy
76
what percent of patients with lingual thyroid is that tissue the ONLY thyroid tissue they have?
70%
77
**PHOTO** what is the classical physical exam findings with thyroglossal duct cysts?
moves upward with swallowing
78
what are two complications of thyroglossal duct cysts?
susceptible to infection and may be premalignant
79
**PHOTO** what is the treatment of thyroglossal duct cyst?
resection --> Sistrunk procedure (take midportion / all of hyoid bone along with the thyroglossal duct cyst)
80
what are the advantages of using PTU and/or methimazole for treatment of hyperthyroidism? (3)
good for young patients; small goiters, and mild T3/T4 elevation
81
which antihyperthyroid treatment is safe in pregnancy: propylthiouracil or methimazole?
PTU is safe in pregnancy, methimazole crosses the placenta
82
what is the MOA of PTU?
inhibits peroxidases and prevents iodine-tyrosine coupling
83
what are two side effects of PTU?
aplastic anemia, agranulocytosis
84
what is the class of drugs PTU belongs to?
propylthiouracil is a thioamide
85
what is the MOA of methimazole?
inhibits peroxidases and prevents iodine-typrosine coupliing
86
what are three AEs of methimazole?
cretinism in newborns (crosses placenta); aplastic anemia; agranulocytosis
87
when is radioactive iodine (I-131) a good option to treat hyperthyroidism?
good for patients who are poor surgical risk candidates or are unresponsive to PTU
88
what two patient populations should NOT be treated with radioactive iodine (I-131)?
children or during pregnancy (can traverse the placenta)
89
name five indications for thyroidectomy when treating hyperthyroidism
cold nodules; toxic adenomas / multinodular goiters not responsive to medical therapy; pregnant patients not controlled with PTU; compressive symptoms
90
when is the best time to perform a thyroidectomy on a hyperthyroid pregnant patient and two reasons why
best time to operate is during the second trimester b/c reduced risk of teratogenic effect and premature labor
91
what are the potential effects of performing a subtotal thyroidectomy on a hyperthyroid patient?
can become euthyroid
92
what is another name for Grave's disease?
toxic diffuse goiter
93
which sex has a predisposition to Grave's disease?
women
94
name 8 S/Sx a/w Grave's disase
exopthalmos, pretibial edema, Afib, heat intolerance, thirst, increased appetite, weight loss, sweating, palpitations
95
what percent of cases of hyperthyroidism are 2/2 Grave's disease?
80%
96
what is the MCC of hyperthyroidism?
Grave's disease
97
what is the underlying pathophysiology of Grave's disease
IgG antibodies to the TSH resceptor (long-acting thyroid stimulator / thyroid-stimulating immunoglobulin)
98
how do you diagnose Grave's disease?
decreased TSH, increased T3/T4, increased LATS level (long-acting thyroid stimulator); diffusely increased Iodine-123 uptake (thyroid scan)
99
what are the first, second, and third-line therapies for Grave's disease?
first-line: thioamides; second-line: radioactive iodine 131; third-line: thyroidectomy if medical therapy fails
100
what is the rate of recurrence of Grave's disease treated with thioamides?
50% recurrence
101
what is the recurrence rate of Grave's disease treated with radioactive iodine 131?
5%
102
what is the rate of recurrence of Grave's disease after bilateral subtotal thyroidectomy?
5%
103
what is the MC reason to need to operate on a patient with Grave's disease?
suspicious nodule
104
what is the preop preparation required prior to surgical treatment of Grave's disease?
PTU until euthyroid. Once euthyroid --> beta blocker, Lugol's solution x 14 days to decrease friability and vascularity
105
what are the two operative procedures to treat Grave's disease?
bilateral subtotal thyroidectomy or total thyroidectomy
106
what do Grave's disease patients require s/p total thyroidectomy?
lifetime thyroxine replacement
107
name the five indications for thyroid surgery in Grave's disease. What is the MCC?
MCC = suspicious thyroid nodule. Others are noncompliant patient, recurrence after medical therapy, children, pregnant women not controlled with PTU
108
what age and sex does toxic multinodular goiter tend to present in?
women over age 50
109
name four S/Sx of toxic multinodular goiter
tachycardia, weight loss, insomnia, airway compromise
110
what exogenous substance can trigger the S/Sx of toxic multinodular goiter?
contrast dyes
111
what is the underlying pathophysiology of toxic multinodular goiter
thyroid hyperplasia secondary to chronic low-grade TSH stimulation
112
what is the preferred initial treatment for toxic multinodular goiter?
surgery: subtotal or total thyroidectomy
113
what treatment of toxic multinodular goiter should be considered before surgery? in what patient population in particular?
consider a trial of iodine 131 (radioactive), especially inthe elderly and rfrail
114
what are two indications for surgery over radioactive iodine to treat toxic multinodular goiter
if airway compression or a suspicious nodule are present
115
what age and sex do single toxic thyroid nodules present?
in younger women
116
what size to single toxic thyroid nodules need to be to produce symptoms?
> 3cm
117
what is the underlying pathophysiology of single toxic thyroid nodules
function autonomously
118
how do you diagnose a single toxic thyroid nodule?
thyroid scan will show a hot nodule
119
what percentage of hot thyroid nodules eventually cause symptoms?
20% of thyroid nodules eventually cause symptoms
120
what are the first and second-line treatments for single toxic thyroid nodules
thioamides and iodine 131 first line (95% effective); lobectomy if medical therapy ineffective
121
name two rare causes of hyperthyroidism
trophoblastic tumors; TSH-secreting pituitary tumors
122
what is the MCC of hypothyroidism in adults?
Hashimoto's thyroiditis
123
what are the physical exam findings in Hashimoto's thyroiditis?
enlarged gland, painless, chronic thyroiditis
124
what are the pathologic findings of Hashimoto's thyroiditis
thyroid tissue has a lymphocytic infiltrate
