Thyroid Flashcards
0
Q
What is the most fascinating anatomical aspect of the thyroid gland?
A
It is the largest endocrine gland.
1
Q
What is the length of the thyroid?
A
40-60 mm
2
Q
What is the width of the thyroid?
A
20-30 mm
3
Q
What is the height of the thyroid?
A
15-20 mm
4
Q
What is the pyramidal lobe and what percentage have one?
A
An extension of the isthmus in between the right and left lobes, 10-40% have one.
5
Q
What is the weight of the thyroid?
A
15-25 grams
6
Q
What are the dimensions of the isthmus?
A
2-6 mm in height (length is variable)
7
Q
What ligament connects hyoid bone and thyroid cartilage?
A
Cricothyroid ligament
8
Q
Which cartilage is below thyroid cartilage and behind the pyramidal lobe?
A
Cricoid cartilage.
9
Q
What is the thyroid covered by?
A
Strap muscles (sternothyroid, sternohyoid, omohyoid)
10
Q
What is the thyroid covered by laterally?
A
Sternocleidomastoid
11
Q
Which 2 strap muscles connect to the hyoid bone?
A
Digastric and stylohyoid
12
Q
Which 2 strap muscles travel from hyoid bone and past the larynx on the left side?
A
Thyrohyoid and sternothyroid
13
Q
Which 2 strap muscles pass the larynx on the right side?
A
Lateral to medial: omohyoid, sternohyoid
14
Q
Where does blood supply for the inferior thyroid artery come from?
A
From thyrocervical artery which comes from subclavian venous drain to internal jugular vein and innominate.
15
Q
What is the BMR which is regulated by the thyroid?
A
Basal metabolic rate
16
Q
What does the thyroid regulate especially in fetus and infants?
A
Body metabolism, growth and development
17
Q
What elements does the thyroid regulate?
A
Body calcium and phosphate
18
Q
What does the thyroid element regulation oppose the action of?
A
Parathyroid hormones
19
Q
Which hormone stimulates the thyroid?
A
TSH from the anterior pituitary gland
20
Q
Which hormones are directly produced by the thyroid?
A
T3 (thyroxine)
T4 (triiodothyronine)
21
Q
What is produced by the parafollicular cells?
A
Calcitonin which decreases serum calcium
22
Q
What does the thyroid follicle contain?
A
Thyroglobulin
23
Q
Where are the parathyroid glands located?
A
Posterosuperior and postero inferior of thyroid
24
What are the dimensions of the parathyroid glands?
5 X 3 X 1 mm
25
How are the parathyroid glands viewed on ultrasound?
They are nonvisible, hypoechoic to the thyroid
26
Concerning parathyroid, what is PTH and what does it do?
Partahormone or parathyrin increases serum calcium (as opposed to calcitonin which decreases calcium)
27
Thyroid hormone provides feedback to what?
The pituitary and hypothalamus of the brain
28
What is TRH?
Thyrotropin-releasing hormone
29
What does TRH do?
Stimulates the release of TSH
30
What does TSH do?
Stimulates the production of thyroid hormone (which provides feedback to brain again)
31
Which transducer do you use?
7-10 MHz (12-13 for skinny)
32
How is the thyroid seen on ultrasound?
Mid to high echogenicity, muscles are hypoechoic with striations
33
What should PRF be set to for thyroid?
3-6 cm/s
34
What are symptoms of hypothyroidism?
Coarse, dry hair
Thin lateral eyebrows
Periorbital edema
Puffy face with dry skin
35
What are 3 causes of hypothyroidism?
Autoimmune (Hashimoto)
Iodine deficiency
Hypothalamus or pituitary disorders
36
What do lab results of hypothyroidism show?
Low T3 and T4 with high TSH
37
What manifestations show in hypothyroidism?
Slow activity in organs, hair loss and myxedema
38
How does hypothyroidism appear on ultrasound?
Small/normal/large heterogenous echogenicity
39
What is the most common cause of hypothyroidism in US?
Hashimoto thyroiditis
40
How does Hashimoto affect women differently than men?
41
What is the sonographic appearance of Hashimoto?
The gland is often enlarged, the parenchyma is coarsened/hypoechoic and often HYPERvascular
42
What is highly diagnostic of Hashimoto?
A micronodular pattern with a positive predictive value of 95%
43
How does the appearance of Hashimoto change over time (U/S)?
In the early stage, vascular may increase. Over time the thyroid becomes fibrotic, ill-defined, heterogenous/hypovascular.
44
In hyperthyroidism, what causes an increase in thyroid hormones?
Graves' disease (toxic adenoma) and de Quervain's thyroiditis, trophoblastic tumor
45
How does hyperthyroidism manifest?
Hypermetabolic state, exophthalmos/proptosis (eyes/eyelids)
46
What do lab results show for hyperthyroidism?
High T3 and/or T4 and low TSH
47
How does hyperthyroidism appear on ultrasound?
Variable according to cause
48
How does de Quervain's present?
Enlarged thyroid with pain and tenderness (subsides in weeks➡️months)
49
What's another term for Graves Disease?
Thyrotoxicosis
50
Which autoimmune disease is the most common cause of hyperthyroidism?
Graves characterized by a triad of hyperthyroidism, diffuse toxic goiter and exophthalmos
51
How does Graves appear on ultrasound?
Hypoechoic enlargement (no palpable nodule) with severe hypervascularity
52
What is another term for severe hypervascularity in the thyroid?
Thyroid inferno
53
What size makes the thyroid palpable?
Double in size (triple to be externally visible)
54
What is goiter and what is it due to?
An enlarged thyroid due to diffuse thyroiditis/iodine deficiency
Multinodular
Cystic
Neoplasm
55
What kind of goiter is almost always benign?
Multinodular without central blood vessels
56
What percentage of solitary nodules are cystic and what are they characterized by?
20% and are anechoic, well-defined border with posterior enhancement
57
What can happen to a cyst with a hemorrhage?
It will appear hypoechoic with debris
58
What size of a cyst is probably benign?
59
What is the most common true thyroid neoplasia?
Adenoma
60
Where does the thyroid originate during embryonic development?
Median, entodermal diverticulum during 3rd week at the level of 1st/2nd pharyngeal pouches of the pharynx ventral walls
61
When do thyroid follicles begin to form?
By week 8
62
When do colloid tissues begin to form on the thyroid?
By the 3rd month
63
During embryology, where does the thyroid end up migrating?
Base of the neck opposite to the 5th to 7th cervical vertebrae
64
Where do parathyroid develop from?
3rd and 4th pharyngeal pouches
65
Where to parathyroid glands originating from the 3rd pouch come to rest?
Dorsal and inferior surface of the thyroid
66
Where to parathyroid glands originating from the 4th pouch come to rest?
Dorsal surface of upper thyroid (superior parathyroid)
67
Where does the thymus descend?
Thorax and lies posterior to sternum, anterior to great vessels and pericardium
68
Where do both lobes lie in relation to the trachea and esophagus?
Anterolateral
69
Where do both lobes lie in relation to the carotid arteries?
Medial
70
Where do both lobes lie inferior to?
Thyroid cartilage of the larynx
71
What does thyroid consist of?
Colloid and glandular epithelium follicles, connective tissue, nerves, lymphatics, blood vessels and stroma
72
What is the adult size of thyroid?
4 - 6 cm (length), 1.3 - 1.8 cm (AP), 1.5 - 2 cm (width)
73
Which thyroid lobe is usually larger?
Right
75
What is the weight of thyroid?
15 - 25 grams
76
What is the child size of thyroid?
2 -3 cm (length), 0.2 cm - 1.2 cm (AP), 1 - 1.5 cm (width)
77
What is the sonographic appearance of thyroid?
Homogenous, medium to high level echogenicity (testes), vessels appear anechoic
78
Where does the isthmus lie?
Anterior to the trachea
79
What does the isthmus connect?
Lower third of the lobes at the level of 2nd, 3rd, 4th tracheal rings
80
What are the dimensions of the isthmus?
2 - 6 mm (AP)
81
What is the sonographic appearance of the isthmus?
Isoechoic to thyroid glands
82
What is the thyroid covered with?
2 thin layers of connective tissue: false thyroid capsule ( pre tracheal fascia) and true thyroid capsule which adheres to gland surface
83
What are the 3 types of strap muscles?
Sternothyroid, omohyoid, and sternohyoid
84
What is the sonographic appearance of the strap muscles?
Thin, hypoechoic to the gland and appear band - like
85
Where is the sternocleidomastoid located?
Lateral to the thyroid and sternohyoid / sternothyroid
86
What is the sonographic appearance of the sternocleidomastoid?
Large, oval, hypo echoic and echogenic striations similar to muscle
87
Where do strap muscles and sternocleidomastoid lie in relation to the thyroid?
Anterior
88
Where do longus coli, esophagus, trachae and vasculature lie in relation to thyroid?
Posterior
89
Where does longus coli lie in relation to the trachae?
Adjacent (posterior to the thyroid / CCA's)
90
Where does sternothyroid sit in relation to thyroid?
Superficially
91
Where does omohyoid sit in relation to sternothyroid?
Laterally
92
Where does sternohyoid sit in relation to sternothyroid?
Anterior
93
Where is sternocleiodomastoid in relation to thyroid, sternohyoid, and sternothyroid?
Laterally
94
What can longus coli be mistaken for?
Enlarged parathyroid
95
What is the sonographic appearance of longus coli?
Thin, hypoechoic
96
Where does esophagus lie?
Medial to left lobe, posterior to trachae
97
What is the sonographic appearance of the esophagus?
Target sign, peristaltic movement (swallowing)
98
What does the trachae form in relation to thyroid?
Medial border
99
What is the sonographic appearance of the trachae?
Hypoechoic with posterior shadowing (air filled)
100
What are superior thyroid arteries the first branch of?
External carotid artery (supplies superior portion)
101
What is the diameter of the superior thyroid arteries?
1 - 2 mm
102
What is the PSV of superior thyroid arteries?
20 cm/s - 40 cm/s
103
What are the inferior thyroid arteries the largest branch of?
Thyrocervical trunk of the subclavian artery
104
Where do superior and middle thyroid veins drain?
Jugular veins
105
Where does inferior thyroid vein drain?
Innominate veins
106
Where does the pyramidal lobe arise?
Superiorly from the isthmus
107
Which side is more common (pyramidal lobe)?
Left
108
Where is pyramidal lobe seen usually?
Younger patients (atrophies in adulthood)
109
What is the sonographic appearance of pyramidal lobe?
Homogenous and isoechoic to normal thyroid
110
What are the 4 variants of thyroid?
Pyramidal lobe, agenesis, hypoplasia, and ectopia
111
How does hypoplasia develop?
Small gland either due to underdevelopment or atrophy of the gland
112
What is a fifth parathyroid gland?
Supernumerary
113
What is supernumerary gland associated with?
Thymus
114
Where are superior thyroid glands located?
Posterior to the middle third of the thyroid
115
Where are the inferior thyroid glands located?
Posterior to the lower third or the level of thymus
