Thyroid Gland Flashcards
1
Q
What is the arterial blood supply to the thyroid?
A
- Superior thyroid artery (first branch of the external carotid artery)
- Inferior thyroid artery (branch of the thyrocervical trunk)
2
Q
What is the venous drainage of the thyroid?
A
- Superior thyroid vein
- Middle thyroid vein
- Inferior thyroid vein
3
Q
What is the thyroid lobe appendage coursing toward the hyoid bone from around the thyroid isthmus?
A
Pyramidal lobe
4
Q
What percentage of patients have a pyramidal thyroid lobe?
A
50%
5
Q
What veins do you first see after opening the platysma muscle when performing a thyroidectomy?
A
Anterior jugular veins
6
Q
What is the lymph node group around the pyramidal thyroid lobe?
A
Delphian lymph node group
7
Q
What is the thyroid isthmus?
A
Midline tissue border between the left and right thyroid lobes
8
Q
Which ligament connects the thyroid to the trachea?
A
Ligament of Berry
9
Q
What is the IMA artery?
A
Small inferior artery to the thyroid from the aorta or innominate artery
10
Q
What percentage of patients have an IMA artery?
A
3%
11
Q
What is the most posterior extension of the lateral thyroid lobes?
A
Tubercle of Zuckerkandl
12
Q
Which paired nerves must be carefully identified during a thyroidectomy?
A
Recurrent laryngeal nerves, which are found in the tracheoesophageal grooves and dive behind the cricothyroid muscle.
Damage to these nerves paralyzes laryngeal abductors and causes hoarseness if unilateral, and airway obstruction if bilateral
13
Q
What nerve (other than the recurrent laryngeal nerves) is at risk during a thyroidectomy and what are the symptoms?
A
Superior laryngeal nerve.
If damaged, patient will have a deeper and quieter voice.
14
Q
What is TRH?
A
Thyrotropin-Releasing Hormone
Released from the hypothalamus; causes release of TSH
15
Q
What is TSH?
A
Thyroid-Stimulating Hormone
Released by the anterior pituitary; causes release of thyroid hormone from the thyroid
16
Q
What are the thyroid hormones?
A
T3 and T4
17
Q
What is the most active form of thyroid hormone?
A
T3
18
Q
What is the thyroid negative feedback loop?
A
T3 and T4 feed back negatively on the anterior pituitary, causing decreased release of TSH in response to TRH
19
Q
What is the most common site of conversion of T4 to T3?
A
Peripheral (e.g. liver)
20
Q
What is Synthroid (levothyroxine): T3 or T4?
A
T4
21
Q
What is the half-life of Synthroid (levothyroxine)?
A
7 days
22
Q
What do parafollicular cells secrete?
A
Calcitonin
23
Q
What percentage of people have a thyroid nodule?
A
5%
24
Q
What is the differential diagnosis of a thyroid nodule?
A
Multinodular goiter, adenoma, hyperfunctioning adenoma, cyst, thyroiditis, carcinoma, lymphoma, parathyroid carcinoma
25
What are 3 types of non-thyroidal neck masses?
1. Inflammatory lesions (e.g. abscess, lymphadenitis)
2. Congenital lesions (e.g. thryoglossal duct, branchial cleft cyst)
3. Malignant lesions (e.g. lymphoma, metastases, squamous cell carcinoma)
26
What studies can be used to evaluate a thyroid nodule?
U/S (solid or cystic); FNA (cytology); I scintiscan (hot or cold)
27
What is the diagnostic test of choice for a thyroid nodule?
FNA
28
What is the percentage of false negative results on FNA for thyroid nodule?
5%
29
What is meant by a hot vs. cold nodule?
Nodule uptake of IV I-123 or mT-99:
Hot: increased I-123 uptake = functioning or hyperfunctioning nodule
Cold: decreased I-123 uptake = nonfunctioning nodule
30
What are the indications for a I-123 scintiscan?
1. Nodule with multiple non-diagnostic FNAs with low TSH
| 2. Nodule with thyrotoxicosis and low TSH
31
What is the role of thyroid suppression of a thyroid nodule?
Diagnostic and therapeutic (administration of thyroid hormone suppresses TSH secretion, and up to half of the benign thyroid nodules will disappear)
32
In evaluating a thyroid nodule, which history findings suggest thyroid carcinoma?
1. Neck radiation
2. Family history (thyroid cancer, MEN-II)
3. Young age (especially children)
4. M > F
33
In evaluating a thyroid nodule, which signs suggest thyroid carcinoma?
1. Single nodule
2. Cold nodule
3. Increased calcitonin levels
4. LAD
5. Hard, immobile nodule
34
In evaluating a thyroid nodule, which symptoms suggest thyroid carcinoma?
1. Voice change
2. Dysphagia
3. Discomfort (in neck)
4. Rapid enlargement
35
What is the most common cause of thyroid enlargement?
Multinodular goiter
36
What are indications for surgery with multinodular goiter?
Cosmetic deformity, compressive symptoms, cannot rule out cancer
37
What is Plummer's disease?
Toxic multinodular goiter
38
What percentage of cold thyroid nodules are malignant?
25% in adults
39
What percentage of multinodular masses are malignant?
1%
40
What is the treatment of a patient with a history of radiation exposure, thyroid nodule, and negative FNA?
Most experts would remove the nodule surgically
41
What should be done with thyroid cyst aspirate?
Send to cytopathology
42
What are the 5 main types of thyroid carcinoma?
1. Papillary carcinoma (80%)
2. Follicular carcinoma (10%)
3. Medullary carcinoma (5%)
4. Hurthle cell carcinoma (4%)
5. Anaplastic carcinoma (1-2%)
43
What are the signs and symptoms of thyroid carcinoma?
Mass or nodule, LAD (most euthyroid)
44
What comprises the workup of thyroid carcinoma?
FNA, thyroid U/S, TSH, Ca level, CXR, +/- I-123 scintiscan
45
What oncogenes are associated with thyroid cancers?
Ras gene family and RET proto-oncogene
46
What is the most common thyroid cancer?
Papillary carcinoma
47
What is the environmental risk factor for papillary carcinoma?
Radiation exposure
48
What is the average age for papillary thyroid carcinoma?
30-40 years
49
What is the sex distribution for papillary thyroid carcinoma?
M:F = 1:2
50
What are the associated histologic findings with papillary thyroid carcinoma?
Psammoma bodies
51
What is the route and rate of spread of papillary thyroid carcinoma?
Most spread slowly via lymphatics (cervical adenopathy)
52
What is the I-131 uptake by papillary thyroid carcinoma?
Good uptake
53
What is the 10-year survival rate for papillary thyroid carcinoma?
95%
54
What is the treatment for a papillary thyroid tumor < 1.5 cm with no history of neck radiation exposure?
Options:
1. Thyroid lobectomy and isthmectomy
2. Near-total thyroidectomy
3. Total thyroidectomy
55
What is the treatment for a papillary thyroid tumor > 1.5 cm, bilateral, positive cervical node metastasis, or a history of radiation exposure?
Total thyroidectomy
56
What is the treatment for lateral palpable cervical lymph nodes in papillary thyroid carcinoma?
Modified neck dissection (ipsilateral)
57
What is the treatment for central palpable cervical lymph nodes in papillary thyroid carcinoma?
Central neck dissection
58
Do positive cervical nodes affect the prognosis for in papillary thyroid carcinoma?
No
59
What is a lateral aberrant thyroid in papillary cancer?
Misnomer (it is metastatic papillary carcinoma to a lymph node)
60
What postoperative medication should be administered for papillary thyroid carcinoma?
Thyroid hormone replacement, to suppress TSH
61
What is a postoperative treatment option for in papillary thyroid carcinoma?
Postoperative I-131 scan can locate residual tumor and distant metastasis that can be treated with ablative doses of I-131
62
What is the most common site of distant metastases of papillary thyroid carcinoma?
Lung
63
What are the P's of papillary thyroid cancer?
```
Papillary cancer
Popular (most common)
Psammoma bodies
Palpable lymph nodes
Positive I-131 uptake
Positive prognosis
Postoperative I-131 scan to diagnose metastases
Pulmonary metastases
```
64
What is the nodular consistency in follicular thyroid carcinoma?
Rubbery, encapsulated
65
What is the route of spread for follicular thyroid carcinoma?
Hematogenous, more aggressive than papillary carcinoma
66
What is the male:female ratio for follicular thyroid carcinoma?
1:3
67
What is the I-131 uptake by follicular thyroid carcinoma?
Good uptake
68
What is the overall 10-year survival rate for follicular thyroid carcinoma?
85%
69
Can the diagnosis of follicular thyroid carcinoma be made by FNA?
No (tissue structure is needed for a diagnosis of cancer)
70
What histologic findings define malignancy in follicular thyroid carcinoma?
Capsular or blood vessel invasion
71
What is the most common site of distant metastasis for follicular thyroid carcinoma?
Bone
72
What is the treatment for follicular thyroid carcinoma?
Total thyroidectomy
73
What is the postoperative treatment option for malignant follicular thyroid carcinoma?
Postoperative I-131 scan for diagnosis/treatment
74
What are the 4 F's of follicular thyroid carcinoma?
```
Follicular thyroid carcinoma
Far-away metastasis (spread hematogenously)
Female (3:1)
FNA…NOT
Favorable prognosis
```
75
What is Hurthle cell thyroid cancer?
Thyroid cancer of the Hurthle cells
76
What is the cell of origin in Hurthle cell thyroid cancer?
Follicular cells
77
What is the I-131 uptake in Hurthle cell thyroid cancer?
No uptake
78
How is the diagnosis of Hurthle cell thyroid cancer made?
FNA can identify cells, but malignancy can be determined only by tissue histology
79
What is the route of metastasis in Hurthle cell thyroid cancer?
Lymphatic > hematogenous
80
What is the treatment for Hurthle cell thyroid cancer?
Total thyroidectomy
81
What is the 10-year survival rate for Hurthle cell thyroid cancer?
80%
82
With what conditions is medullary thyroid cancer associated?
MEN-II
83
What is the histology of medullary thyroid cancer?
Amyloid
84
What does a medullary thyroid tumor secrete?
Calcitonin
85
What is the appropriate stimulation test for medullary thyroid cancer?
Pentagastrin (causes an increase in calcitonin)
86
What is the route of spread in medullary thyroid cancer?
Lymphatic and hematogenous distant metastasis
87
How is the diagnosis of medullary thyroid cancer made?
FNA
88
What is the I-131 uptake in medullary thyroid cancer?
Poor uptake
89
What is the associated genetic mutation in medullary thyroid cancer?
RET proto-oncogene
90
What is the male:female ratio with medullary thyroid cancer?
1:1.5
91
What is the 10-year survival rate for medullary thyroid cancer?
Without LN involvement: 80%
| With LN spread: 45%
92
What should all patients with medullary thyroid cancer also be screened for?
MEN-II: pheochromocytoma, hyperparathyroidism
93
If medullary thyroid cancer and pheochromocytoma are found, which one is operated on first?
Pheochromocytoma
94
What is the treatment for medullary thyroid cancer?
Total thyroidectomy and median lymph node dissection.
| Modified neck dissection, if lateral cervical nodes are positive.
95
What are the M's of medullary thyroid cancer?
```
Medullary thyroid cancer:
MEN-II
aMyloid
Median lymph node dissection
Modified neck dissection if lateral nodes are positive
```
96
What is anaplastic thyroid carcinoma also known as?
Undifferentiated carcinoma
97
What is anaplastic thyroid carcinoma?
Undifferentiated cancer arising in 75% of previously differentiated thyroid cancers (most commonly, follicular carcinoma)
98
What is the male:female ratio with anaplastic thyroid carcinoma?
F > M
99
What are the associated histologic findings with anaplastic thyroid carcinoma?
Giant cells, spindle cells
100
What is the I-131 uptake in anaplastic thyroid carcinoma?
Very poor uptake
101
How is the diagnosis of anaplastic thyroid carcinoma made?
FNA
102
What is the major differential diagnosis for anaplastic thyroid carcinoma?
Thyroid lymphoma
103
What is the treatment of small anaplastic thyroid tumors?
Total thyroidectomy, XRT/chemotherapy
104
What is the treatment for anaplastic thyroid carcinoma with airway compromise?
Debulking surgery and tracheostomy, XRT/chemotherapy
105
What is the prognosis for anaplastic thyroid carcinoma?
Dismal, most patients are stage IV
106
What laboratory value must be followed postoperatively after a thyroidectomy?
Calcium (decrease secondary to parathyroid damage; during lobectomy, the parathyroids must be spared and their blood supply protected; if blood supply is compromised intra-operatively, they can be autografted into the SCM or forearm)
107
What is the differential diagnosis of postoperative dyspnea after a thyroidectomy?
Neck hematoma (remove sutures and clot at the bedside); Bilateral recurrent laryngeal nerve damage
108
What is a lateral aberrant rest of the thyroid?
Misnomer: it is a papillary cancer of a lymph node from metastasis
109
What is the most common cause of hyperthyroidism?
Graves' disease
110
What is Graves' disease?
Diffuse goiter with hyperthyroidism, exophthalmos, and pretibial myxedema
111
What is the etiology of Graves' disease?
Caused by circulating antibodies that stimulate TSH receptors on follicular cells of the thyroid and cause deregulated production of thyroid hormones
112
What is the male:female ratio for Graves' disease?
1:6
113
What specific physical exam finding is associated with Graves' disease?
Exophthalmos
114
How is the diagnosis of Graves' disease made?
Increased T3,T4 and anti-TSH receptor antibodies, decreased TSH, global uptake of I-131 radionuclide
115
What are treatment option modalities for Graves' disease?
1. Medical blockade (iodide, propranolol, PTU, methimazole, Lugol's solution)
2. Radioiodide ablation (most popular)
3. Surgical resection (bilateral subtotal thyroidectomy)
116
What are the possible indications for surgical resection in Graves' disease?
Suspicious nodule.
| If patient is noncompliant or refractory to medicines, pregnant, a child, or if patient refuses radioiodide therapy.
117
What is the major complication of radioiodide or surgery for Graves' disease?
Hypothyroidism
118
What does PTU stand for?
PropylThioUracil
119
How does PTU work?
1. Inhibits incorporation of iodine into T4/T3 (by blocking peroxidase oxidation of iodide to iodine)
2. Inhibits peripheral conversion of T4 to T3
120
How does methimazole work?
Inhibits incorporation of iodine into T4/T3 only (by blocking peroxidase oxidation of iodide to iodine)
121
What is toxic multinodular goiter also known as?
Plummer's disease
122
What is toxic multinodular goiter?
Multiple thyroid nodules with one or more nodules producing thyroid hormone, resulting in hyperfunctioning thyroid
123
What medications may bring on hyperthyroidism with a multinodular goiter?
Amiodarone (or any iodine-containing medication or contrast)
124
How the hyperfunctioning nodule localized?
I-131 radionuclide scan
125
What is the treatment for toxic multinodular goiter?
Surgically remove hyperfunctioning nodule(s) with lobectomy or near total thyroidectomy
126
What is Pemberton's sign?
Large goiter causes plethora of head with raising of both arms
127
What are the features of acute thyroiditis?
Painful, swollen thyroid, fever, overlying skin erythema, dysphagia
128
What is the cause of acute thyroiditis?
Bacteria (usually Staph or Strep), usually caused by a thyroglossal fistula or anatomic variant
129
What is the treatment of acute thyroiditis?
Antibiotics, drainage of abscess, needle aspiration for culture.
Most patients need definitive surgery later to remove the fistula.
130
What are the features of subacute thyroiditis?
Glandular swelling, tenderness, often follows URI, elevated ESR
131
What is the cause of subacute thyroiditis?
Viral infection
132
What is the treatment of subacute thyroiditis?
Supportive (NSAIDs, +/- steroids)
133
What is De Quervain's thyroiditis?
Another name for subacute thyroiditis caused by a virus
134
What are the common causative bacteria in acute suppurative thyroiditis?
Streptococcus or Staphylococcus
135
What are the two types of chronic thyroiditis?
1. Hashimoto's thyroiditis
| 2. Riedel's thyroiditis
136
What are the features of Hashimoto's thyroiditis?
Firm and rubbery gland, 95% in women, lymphocyte invasion
137
What is the most common cause of hypothyroidism in the US?
Hashimoto's thyroiditis
138
What is the etiology of Hashimoto's disease?
Autoimmune
139
What lab tests should be performed to diagnose Hashimoto's disease?
Antithyroglobulin and microsomal antibodies
140
What is the medical treatment for Hashimoto's thyroiditis?
Thyroid hormone replacement if hypothyroid (surgery is reserved for compressive symptoms and/or if cancer needs to be ruled out)
141
What is Riedel's thyroiditis?
Benign inflammatory thyroid enlargement with fibrosis of thyroid.
Patients present with painless, large thyroid, which may involve other tissue.
142
What is the treatment for Riedel's thyroiditis?
Surgical tracheal decompression, thyroid hormone replacement as needed, possibly steroids/tamoxifen if refractory
