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Thyroid Flashcards

0
Q

where is the thyroid located?

A

anteriorinferior neck at level of thyroid cartliage

rt and lt lobe

joined by isthmus

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1
Q

What is the function of the thyroid?

A

synthesiszes, stores and secretes hormones through tissue/blood - not ducts

control BMR - basial metabolic rate

maintains metabolism growth and development

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2
Q

what is the third lobe of the thyroid that some people have?

A

pyramidal lobe - arises from isthmus

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3
Q

how does the thyroid interact with the trachea?

A

straddles trachea anteriorly

bounded laterally by carotid arteries and jugular veins

pyramidal lobe arises from isthmus

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4
Q

When does the thyroid develop prenatally?

A

in the third week

thyroglossal duct -connects thryoid to tongue and atrophies by 8th week - if it persists = cysts, fistulas, pyramidal lobe

ectopic tissue

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5
Q

What is the shape of the thyroid?

A

U or H shaped

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6
Q

Which lobe is larger rt or lt, male or female?

A

Right is larger

Females > males

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7
Q

what is the normal size of the thyroid?

A

4-6cm (L) x 1.3-1.8cm (AP) x 1.5-2cm (W)

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8
Q

What is the relational anatomy to the thyroid?

Review/learn slide 12

A

anterior: strap muscles (sternohyoid, omohyoid, sternothyroid)*

sternocleidomastoid muscle

posterolateral: CCA, IJV, *longus colli muscle

Medial: larynx, trachea, esophagus

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9
Q

What is the blood supply to the thyroid?

A

highly vascular

two superior thyroid arteries from ECA descend to upper poles

two inferior thyroid arteries from subclavian and ascend to lower poles

corresponding veins drain into IJV

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10
Q

What role does iodine play in they thyroid function?

A

processed by follicular cells to manufacture, store and secrete thyroid hormones

(the thyroid maintains body metabolism, growth and development)

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11
Q

What hormones does the thyroid produce?

A

T3 triiodothyronine

T4 thyroxine

when thyroid hormone is needed by the body it is released into the blood stream by action of thyrotropin or thyroid stimulating hormone (TSH), produced by the pituitary gland

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12
Q

What is calcitonin?

A

decreases concentration of calcium in blood by first acting on bone to inhibit its breakdown

helps maintain homeostasis of blood calcium

secreted by C-cells or parafollicular cells

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13
Q

Which thyroid hormone is most potent T3 or T4

A

T3 - 10% produced - most potent

T4 - 90% produced less potent

both stored in colloid

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14
Q

what does Euthyroid mean?

A

the correct amount of hormone production

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15
Q

What causes hypothyroidism?

A

undersecretion of hormones

low intake of iodine

inability of thyroid to produce thyroid hormone

chronic autoimmune thyroiditis

pituitary gland or hypothalamus diseases

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16
Q

What are the clinical signs of the hypothyroidism?

A

myxedema: nonpitting waxy edema of the skin on the face and shins

weight gain

hair loss

tissue around eyes

lethargy

intellectual and motor slowing

cold intolerance

constipation

hoarseness

dry skin

menstrual irregularities

decrease sweating

bradycardia

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17
Q

What is the sonographic appearance of hypothyroid?

A

diffusely abnormal

decreased heterogeneous echogenicty

normal

enlarged with irregular surface

small calcifications

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18
Q

What is hyperthyroidsim?

A

over-secretion of thyroid hormones

entire gland out of control

Graves’ disease

localized neoplasm causes overproduction of hormones:

trophoblastic tumors: hydatidiform mole, choriocarcinoma, some testicular tumors

toxic adenomas

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19
Q

what are the clinical symptoms of hyperthyroidism?

A

dramatic ^ in metabolic rate

weight loss despite ^ in appetite

nervous energy

tremor

excessive sweating

heat intolerance

tachycardia/palpitation

exophthalmos - bulging eyes and retraction of eyelids

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20
Q

what is the sonographic appearance of hyperthyroidism?

A

normal sized or enlarged gland

inhomogeneous

hypervascularity - key sign for Graves’ disease

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21
Q

What are the thyroid function tests?

A

nuclear medicine

blood tests to measure T3 and T4

US does not evaluate function

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22
Q

What is a “hot” nodule from a nuc med scan?

A

hyperfunctioning nodule

5-10% of all nodules - usually benign

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23
Q

What is a “cold” nodule from a nuc med scan?

A

non-functioning

80-85% of all nodules – 10-15% of these are malignant

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24
What controls the secretion of TSH and what produces it?
controls: thyrotropin releasing hormone (TRH) Produced: hypothalamus
25
What is the most common pathology of the thyroid?
iodine deficiency
26
What does an iodine deficiency lead to?
goiter formation hypothyroidism
27
if its not iodine deficiency, what else can cause hypothyroidism and hyperthyroidism?
autoimmune disorders
28
What is a goiter?
diffuse enlargement of thyroid peak age 35-50 yrs old females 3:1 hamper hormone secretion may become very large endemic goiter
29
what percent of thyroid disease is caused by hyperplasia of the gland?
80%
30
What are the different types of goiters?
nodular hyperplasia multinodular goiter adenomatous hyperplasia simple/non-toxic multinodular toxic
31
what is multinodular/ toxic goiter?
may be spontaneous may be end stage of simple goiter enlarged heterogenous slide 44 for image focal scarring, ischemia, necrosis, cyst formation, calcifications asymmetry
32
What causes goiters?
iodine deficiency thyroid hormone deficiency grave's disease thyroiditis neoplasm cyst
33
What is a non-toxic simple goiter?
diffuse uniform enlargement iodine deficiency - gland unable to supply adequate hormones dietary shortage or gland malfunction may lag behind = hypothyroidism often gland keeps up with demand and provides normal release of hormones
35
What are the labs for grave's disease?
increase T3 and T4
36
What is thyroiditis?
swelling and tenderness infection or autoimmune two types: De Quervain's (viral) Hashimoto's (destructive autoimmune disorder)
37
What is De Quervain's (subacute granulomatous thyroiditis)?
fever enlarged gland pain on palpation pain may radiate to ear or jaw
38
what is Hashimoto's (chronic autoimmune lymphocytic)? see slide 52 for image
painless onset diffusely enlarged gland young to middle age females heterogeneous as progresses and tenderness eventual severe gland damage = hypothyroidism ***most common cause in adults***
39
How does Hashimoto's appear sonographically?
hypoechoic, coarse and homogeneous thickened fibrous strands - chronic sign increased color flow - in acute stage fibrotic, ill-defined and heterogeneous over time increased risk for malignancy
40
What are the benign lesions of the thyroid?
Palpable nodule - ****most common cause for US**** Cysts - degeneration of follicular adenoma, may have debris adenoma - neoplasm, complete fibrous encapsulation, more often females, may have appearance of peripheral halo, may cause hyperfunction
41
What are cysts?
10-15% of solitary nodules common - colloid or degeneration or necrosis of adenomatous nodules benign if < 4 cm
42
What is an adenomas?
true benign neoplasm encapsulated solitary well - defined females MOST COMMON THYROID NEOPLASM "COLD" nuc med nodule
43
what are the different types of adenomas
embryonal fetal colloid follicular hyperplastic
44
What is carcinoma of the thyroid?
malignant rare most common 40-60 yrs risk of malignancy decreases with multiple nodules variable in appearance ***calcifications present 50-80% of all types*** non shadowing females especially suspicious single nodules and under 14 yrs old and over 65 yrs old
45
What is papillary carcinoma?
most common form of malignant thyroid cancer see slide 65 for image 3rd and 7th decades of life females predominant thyroid cancer in children 25% laminate calcifications 20% metastatic cervical adenopathy (check those lymph nodes!!) least aggressive hypoechoic microcalcifications hypervascularity cervical lymph node metastasis
46
what shape are healthy lymph nodes? suspicious?
oval/flat round
47
What is follicular carcinoma?
more aggressive than papillary females solid nodule sonographically = irregular, firm, nodular enlargement metastases to lung, bone and other distant sites
48
What is medullary carcinoma?
5% of thyroid cancers hard bulky mass, enlargement sonographically = bright enchogenic foci within solid mass associated with elevated serum calcitonin and multiple endocrine neoplasm (MEN) type II
49
What is anaplastic carcinoma?
rare, <2% occurs after age 50 ***most lethal*** hard fixed mass with rapid growth invades neck structures, causing death by compression and asphyxiation 6months - 1 year life expectancy
50
what is lymphoma?
primarily Non-hodgkin's type older females s sonographically = nonvascular hypoechoic mass, adjacent thyroid heterogeneous
51
what is the parathyroid anatomy?
four individual glands PAIRED together (2 at the top, 2 at the bottom) 2 posterior superior poles, 2 posterior inferior poles may be in neck/mediastinum flat and disc shaped
52
Where is the location of the parathyroid?
medial and posterior to the thyroid gland (closest to the trachea)
53
What are the sonographic findings of the parathyroid glands?
not usually seen, isochoic to thyroid 5mm enlarged, hypoechoic ***enlongated masses between posterior longus colli and anterior thyroid****
54
What is the parathyroid physiology?
calcium sensing organs produce (PTH) parathyroid hormone serum calcium decrease PTH^ PTH acts on bone, kidney and intestine to enhance calcium absorption unexplain hypercalcemia = US
55
what is primary hyperparathyroidism?
increased function of the parathyroid glands females ^ PTH from an adenoma, hyperplasia or carcinoma primary hyperplasia - hyperfunction without and apparent cause
56
What is secondary hyperparathyroidism?
chronic hypocalcemia from renal failure, vitamin D deficiency or malabsorption syndromes compensatory reaction leads to PTH stimulation includes all 4 glands primary hyperplasia - parathyroid
57
what is a parathyroid adenoma?
***most common cause of primary hyperparathyroidism*** 80% sonographically - hypoechoic, solid, encapsulated, discrete borders cannot discern adenoma from cancer
58
What is a thyroglossal duct cyst? see slide 85 for image
congenital anomaly midline and anterior to trachea remnant of tubular development sonographically: cystic mass anterior to trachea oval or spherical masses rarely larger than 2 or 3 cm
59
What is branchial cleft cysts?
remnant of embryologic development tract from pharyngeal cavity to auricle results in cystic formation lateral to thyroid gland may present with solid components especially if infected see slide 88 for image
60
What is an ascess?
can be anywhere in the neck wide range of appearances most common - low level echogenicity and irregular walls increased blood flow check for air shadowing
61
What is adenopathy?
shape of node should be oval homogeneous with central core echo complex more round ? malignant has the patient been scratched any where echo-free node ? inflammatory process fine needle aspiration to confirm
62
What does an abnormal lymph node look like?
loss of fatty hilum irregular margins cystic areas of degeneration calcifications round > 7mm width or AP
65
What is Grave's disease?
female > 30 autoimmune most frequent cause of hyperthyroidism ***triad - diffuse toxic goiter, exopthalmos, dermis thickening*** sonographically - hypoechoic, diffuse homogeneous enlargement, increase color flow ***"thyroid inferno"***because of the increased color flow on doppler

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