Thyroid Flashcards
where is the thyroid located?
anteriorinferior neck at level of thyroid cartliage
rt and lt lobe
joined by isthmus
What is the function of the thyroid?
synthesiszes, stores and secretes hormones through tissue/blood - not ducts
control BMR - basial metabolic rate
maintains metabolism growth and development
what is the third lobe of the thyroid that some people have?
pyramidal lobe - arises from isthmus
how does the thyroid interact with the trachea?
straddles trachea anteriorly
bounded laterally by carotid arteries and jugular veins
pyramidal lobe arises from isthmus
When does the thyroid develop prenatally?
in the third week
thyroglossal duct -connects thryoid to tongue and atrophies by 8th week - if it persists = cysts, fistulas, pyramidal lobe
ectopic tissue
What is the shape of the thyroid?
U or H shaped
Which lobe is larger rt or lt, male or female?
Right is larger
Females > males
what is the normal size of the thyroid?
4-6cm (L) x 1.3-1.8cm (AP) x 1.5-2cm (W)
What is the relational anatomy to the thyroid?
Review/learn slide 12
anterior: strap muscles (sternohyoid, omohyoid, sternothyroid)*
sternocleidomastoid muscle
posterolateral: CCA, IJV, *longus colli muscle
Medial: larynx, trachea, esophagus
What is the blood supply to the thyroid?
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
What role does iodine play in they thyroid function?
processed by follicular cells to manufacture, store and secrete thyroid hormones
(the thyroid maintains body metabolism, growth and development)
What hormones does the thyroid produce?
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
What is calcitonin?
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
Which thyroid hormone is most potent T3 or T4
T3 - 10% produced - most potent
T4 - 90% produced less potent
both stored in colloid
what does Euthyroid mean?
the correct amount of hormone production
What causes hypothyroidism?
undersecretion of hormones
low intake of iodine
inability of thyroid to produce thyroid hormone
chronic autoimmune thyroiditis
pituitary gland or hypothalamus diseases
What are the clinical signs of the hypothyroidism?
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
What is the sonographic appearance of hypothyroid?
diffusely abnormal
decreased heterogeneous echogenicty
normal
enlarged with irregular surface
small calcifications
What is hyperthyroidsim?
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
what are the clinical symptoms of hyperthyroidism?
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
what is the sonographic appearance of hyperthyroidism?
normal sized or enlarged gland
inhomogeneous
hypervascularity - key sign for Graves’ disease
What are the thyroid function tests?
nuclear medicine
blood tests to measure T3 and T4
US does not evaluate function
What is a “hot” nodule from a nuc med scan?
hyperfunctioning nodule
5-10% of all nodules - usually benign
What is a “cold” nodule from a nuc med scan?
non-functioning
80-85% of all nodules – 10-15% of these are malignant
What controls the secretion of TSH and what produces it?
controls: thyrotropin releasing hormone (TRH)
Produced: hypothalamus
What is the most common pathology of the thyroid?
iodine deficiency
What does an iodine deficiency lead to?
goiter formation
hypothyroidism
if its not iodine deficiency, what else can cause hypothyroidism and hyperthyroidism?
autoimmune disorders
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
what percent of thyroid disease is caused by hyperplasia of the gland?
80%
What are the different types of goiters?
nodular hyperplasia
multinodular goiter
adenomatous hyperplasia
simple/non-toxic
multinodular toxic
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
What causes goiters?
iodine deficiency
thyroid hormone deficiency
grave’s disease
thyroiditis
neoplasm
cyst
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
What are the labs for grave’s disease?
increase T3 and T4
What is thyroiditis?
swelling and tenderness
infection or autoimmune
two types: De Quervain’s (viral) Hashimoto’s (destructive autoimmune disorder)
What is De Quervain’s (subacute granulomatous thyroiditis)?
fever
enlarged gland
pain on palpation
pain may radiate to ear or jaw
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
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
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
What are cysts?
10-15% of solitary nodules
common - colloid or degeneration or necrosis of adenomatous nodules
benign if < 4 cm
What is an adenomas?
true benign neoplasm
encapsulated
solitary
well - defined
females
MOST COMMON THYROID NEOPLASM
“COLD” nuc med nodule
what are the different types of adenomas
embryonal
fetal
colloid
follicular
hyperplastic
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
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
what shape are healthy lymph nodes? suspicious?
oval/flat
round
What is follicular carcinoma?
more aggressive than papillary
females
solid nodule
sonographically = irregular, firm, nodular enlargement
metastases to lung, bone and other distant sites
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
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
what is lymphoma?
primarily Non-hodgkin’s type
older females
s
sonographically = nonvascular hypoechoic mass, adjacent thyroid heterogeneous
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
Where is the location of the parathyroid?
medial and posterior to the thyroid gland (closest to the trachea)
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*
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
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
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
what is a parathyroid adenoma?
most common cause of primary hyperparathyroidism 80%
sonographically - hypoechoic, solid, encapsulated, discrete borders
cannot discern adenoma from cancer
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
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
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
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
What does an abnormal lymph node look like?
loss of fatty hilum
irregular margins
cystic areas of degeneration
calcifications
round
> 7mm width or AP
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
