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Thyroid gland is located in
the neck
isthmus
connects the 2 lateral lobes; narrow section
Pyramidal lobe
3rd love arising from the superior portion of the isthmus; ascends to the level of the hyoid bone
Thyroid epithelial cells
the cells responsible for synthesis of thyroid hormones
arranged in spheres called thyroid follicles
Colloid
follicles are filled with this
a proteinaceous depot of thyroid hormone precursor
Thyroid Hormones secreted
T4, T3, Calcitonin
More than _____ of the T3 and T4 circulating in blood is bound to carrier proteins
99%
calcitonin
hormone produced in the C cells of the thyroid gland which participates in calcium and phosphorus metabolism
Calcitonin reduced blood Ca++ by:
decreasing calcium absorption by intestines, increasing calcium storage in bones, increasing calcium excretion through kidneys
Control of thyroid hormone synthesis and secretion is stimulated by
TSH from anterior pituitary gland
Effects of thyroid hormone
development, growth, metabolism
Euthyroid
normal thyroid
Hypothyroidism
the under-secretion of thyroid hormones; decreased activity of thyroid gland
The most common thyroid function disorder is
hypothyroidism
Hypothyroidism can be caused by
low intake of iodine in the body
inability of the thyroid to produce enough
problem in the pituitary gland that doesn’t properly control thyroid production
Primary hypothyroidism
Most common
caused by defective hormone synthesis, endemic iodine deficiency, iodine excess, inflammatory conditions
secondary hypothyroidism
less common, caused by pituitary adenoma, tumors, irradiation, medication, congenital disorders
Signs and symptoms of hypothyroidism
weight gain, hair loss, lethargy, cold intolerance, muscle cramps, slow metabolic rate, decreased heart rate, increased subcutaneous tissue around eyes
Hyperthyroidism (thyrotoxicosis)
The over-secretion of thyroid hormones; hyperactivity of the thyroid gland
caused by elevated free T3 and T4
Underlying cause of hyperthyroidism in 50-80% of cases is
Graves Disease
Primary hyperthyroidism
form of thyrotoxicosis which excess thyroid hormone is synthesized and secreted by the thyroid itself
Secondary hyperthyroidism
rare, caused by TSH-secreting pituitary adenoma
Signs and symptoms of hyperthyroidism
nervousness, weight loss, tremors, excessive sweating, palpitations, increased heart rate, diarrhea, protruding eyes
T4 and T3 is high in
hyperthyroidism
t4 and t3 is low in
hypothyroidism
TSH is low in
hyperthyroidism
TSH is high in
hypothyroidism
We use ultrasound to
determine size of gland and mass location, differentiating between cystic and solid lesions, FNA
Sonography cant determine the difference of
benign and malignant masses
Normal size of 1 thyroid lobe length
4.0-6.0cm
Normal size of 1 thyroid lobe AP
1.3-1.8cm
Normal size of 1 thyroid lobe width
1.5-2cm
normal size of isthmus
4.0-6.0mm
size of thyroid varies with
gender and body surface area
Normal ultrasound appearance of thyroid
homogenous, medium-level echo pattern
more echogenic than surrounding muscles
fibrous capsule is smooth-bordered
trachea
appears medially as a bright reflector with acoustic reverberation artifacts and shadowinge
esophagus
appears posterolateral and to the left of the trachea as a hypo echoic structure with a central echogenic center; elevates/moves with swallowing
Longus colli
located on the anterior surface of vertebral column
lies posterior to the thyroid lobe and CCA
Sternocleidomastoid muscles
lateral and superficial neck muscles
located anterior and lateral to the thyroid libes
strap muscles
group of long flat neck muscles
located anterior to the thyroid muscles
surrounding musculature appears
hypoechoic compared to normal thyroid tissue
CCA
appears anechoic
located medial to IJV, lateral to thyroid lobe
IJV
located lateral to CCA and thyroid lobe
will enlarge with valsalva maneuver
Superior thyroid artery arises from
external carotid artery
inferior thyroid artery arises from
thyrocerival artery
superior and middle thyroid veins drain into the
Internal jugular vein
inferior thyroid vein drain into the
innominate vein
Athyrosis
absence of the thyroid gland
rare
absent isthmus
complete absence of the isthmus
gland appears as 2 independent lobes
Ectopic thyroid tissue
gland development can occur ectopic anywhere along the pathway of descent
ectopic thyroid tissue is most common under
the tongue
Nodular thyroid disease (goiter)
most common thyroid abnormality
nontoxic goiter refers to
an enlargement involving the entire gland without producing nodularity and with out evidence of functional disturbance
Most common cause of nodular thyroid disease is
iodine deficiency
goiter is the term used for
enlargement of thyroid gland
a goiter may
compress the esophagus and interfere with swallowing or cause pressure on the trachea
nodular thyroid disease are
mostly isoechoic compared to normal thyroid, but as gland enlarges, becomes more hyperechoic
fibrosis or calcification may be present
True epithelium-lined cysts in the thyroid are
uncommon and are almost always benign
thyroid cysts are
cystic degeneration of a preexisting nodule, may become hemorrhagic spontaneously
clinical findings of a cysts are
palpable mass or neck swelling. accounts for the majority of “cold nodules” on nuc med scans
Thyroid adenoma
benign solid neoplastic growth
slow growing
complete fibrous encapsulation
thyroid adenoma appearance on ultrasound
may appear solid but also cystic due to degeneration
most are solitary but may develop as multinodular process
most are well circumscribed; circular or oval
thyroid adenoma commonly have
peripheral halos or calcification along the rim
thyroid carcinoma
rare, solitary nodule may be malignant in small percentages of cases, but risk of malignancy decrease with presence of multiple nodules
types of thyroid carcinoma
papillary, follicular, medullary, anaplastic
thyroid carcinoma signs and symptoms
lump in the neck which feels like hard mass on palpation, history of enlarging goiter, hoarseness, pressure symptoms
thyroid carcinoma has a
highly variable appearance, and depends on which type. calcifications are present in 50-80%. increased vascularity
Papillary carcinoma
most common type of thyroid carcinoma, least agrressive
major route of spread is through lymphatics to nearby cervical lymph nodes.
papillary carcinoma ultrasound appearance
usually hypoechoic and microcalcifications/hypervascularity are present.
follicular carcinoma
second most common type of carcinoma. spreads via the blood stream, usually solitary mass
2 types of follicular carcinoma
minimally invasive: well-encapsulated, focal invasion of capsular blood vessels of fibrous
widely invasive: not encapsulated, invasion of blood vessels and adjacent tissue occurs
follicular carcinoma appearance on ultrasound
irregular margins, thick irregular “halo”, nodular enlargement, tortuous internal blood vessels.
Follicular adenomas and follicular carcinoma’s cant be
distinguished on sonography of FNA. MUST USE HISTOLOGY
medullary carcinoma
rare, neuroendocrine neoplasm that secretes calcitonin.
aggressive
medullary carcinoma appearance
usually hypoechoic solid mass. calcium deposits and microcalcifications are noticed. coarse califications too.
anaplastic carcinoma
rare, highly aggressive, rapid growth. presents as a hard fixed mass. no effective therapy
anaplastic carcinoma ultrasound apperance
large, solid, hypoechoic mass, invasion of surrounding muscles and vessels of the neck
lymphoma
uncommon, primarily the non-hodgkin’s type
symptoms are airway obstruction
usually have hasimotos already
lymphoma ultrasound apperance
large, solid, hypoechoic, lobulated mass
color doppler typically hypovascular/nonvascular.
may compress or infiltrate adjacent thyroid parenchyma.
thyroiditis
swelling and tenderness of the thyroid gland.
caused by infection leading to massive infiltration of lymphocytes into the gland. also can be related to autoimmune disturbances
signs and symptoms of thyroiditis
diffusely enlarged, soft, palpable thyroid, hoarseness, neck swelling, decreased T3 and T4 in 50% cases
thyroiditis ultrasound appearance
diffusely enlarged gland, slightly irregular echo pattern, calcifications may occur after inflammation
subacute thyroiditis
granulomatous, diffuse inflammation following viral infection, benign, occurs transiently, gradual or fairly onset, may have severe pain
subacute thyroiditis signs and symptoms
enlarged, tender thyroid gland, painful swelling, fever, normal WBC count
subacute thyroiditis appearance on ultrasound
may be asymmetric, hypoechoic, discrete areas of increased and decreased echogenicity
Chronic (Reidel’s) thyroiditis
chronic, fibrotic inflammatory process
results in replacement of thyroid tissue with fibrotic tissue and scarring
rare; least common inflammatory process
signs and symptoms of chronic thyroiditis
insidious onset, patients present with pressure from adherence of the gland to the trachea and subcutaneous neck tissue
chronic thyroiditis ultrasound apperance
diffuse enlargement of both lobes and isthmus, heterogeneous echo pattern compared to that of normal gland due to fibrosis and scarring
hashimotos
chronic, progressive, destructive autoimmune disorder leading to chronic inflammation of thyroid
most common form of thyroiditis
signs and symptoms of hashimotos disease
painless, diffusely enlarged gland, mild to moderate tenderness, more common in young-middle aged females
ultrasound apperance of hashimotos
diffuse coarse parenchymal texture that is slightly more hypoechoic than normal thyroid.
ill-defined hypoechoic areas separated by thickened fibrous strands
eventually gland becomes severely damaged
homogenous enlargement initially, then heterogenous
graves disease
thyroid hyperfunction related to production of autoimmune antibodies directed against thyroid
characterized by thyrotoxicosis and is most common cause of hyperthyroidism
causes diffuse cellular hyperplasia
graves disease symptoms
hypermetabolism, increased t3 and t4, cutaneous manifestations, diffuse toxic goiter, protruding of the eyes
ultrasound of graves disease apperance
diffuse enlargement of gland with homogeneous texture, usually hypoechoic, low impedance vascularity
TI-RADS
Thyroid Imaging Reporting And Data System
helps avoid unnecessary cost and patient discomfort
fine needle aspiration (FNA)
ultrasound guided. fine needle attached to syringe
specimens obtained by the capillary action technique which is an up and down motion
core biopsy
ultrasound guided, preserves spatial arrangement of cells. tissue samples obtained using an automated hollow core needle. loud