Chapter 15: Thyroid Gland, Parathyroid Glands, and Neck
What is the most common cause of primary Hypothyroidism?
( malfunction thyroid gland- not producing enough T3 and T4) Where iodine level are sufficient, is chronic autoimmune thyroiditis aka lymphocytic thyroiditis Hashimoto's thyroiditis referred to as Hashimoto's thyroiditis
Agenesis
(A= absent) no thyroid, leads to Cretinism -occurs in one/both lobes, cause of congenital hypothyroidism -causes mental retardation and dwarfism
thyroid-stimulating hormone
(TSH) hormone secreted by the anterior pituitary gland that secretes the thyroid gland to secrete thyroxine (T4) and triiodothyroxine (T3) - thyroid hormones circulate in the blood both free and bound to (TBG)
Name the strap muscles. Which strap muscle is directly anterior to the thyroid?
(a group of pairs of anterior muscles known as the infra hyoid muscles) -Sternothyroid ( most anterior to thyroid) -Thryohyoid -Omohyoid (2 parts) -Sternohyoid
Hypoplasia
(hypo) underdeveloped thyroid gland
Cold Nodule
(photon-deficient area) seen on a nuclear medicine study as a region of thyroid where the radioisotope has not been taken up; the area may correspond to a palatable mass
Embryology Where did the thyroid initially develop?
(the development of the thyroid) earliest endocrine(ductless) glandular structure in embryo, gland develops from an invagination in the floor of the primitive pharynx at the level of the first and second brachial arches, a point in the adult corresponding to the base of the tongue -lined by epithelial cells--> form their pharyngeal connections--> vesicles becomes a solid mass--> severs as its connection with the pharyngeal cavity (this journey leaves= thyroglossal duct)
Why is it necessary to know the volume of the thyroid gland?
(thyroid volume based on the ellipsoid formula with a correction factor) = length x wide x thickness x 0.52 for each lobe Knowing the volume plays an important role in the treatment of thyroid disease using iodine ( knowing how much to give patient) men: 18.6 to 4.5 ml Females: slightly larger
Hypercalcemia + Symptoms
(too much calcium) -created from excessive calcium levels (Low serum calcium levels) -May be asymptomatic and life threatening Symptoms: weight loss, anorexia, nausea, polyuria, More common Symptoms: Mouth paresthesia Digits and muscles spasms in hands and feet Hyperirritability Fatigue Anxiety
Sonographic findings of malignant lesions
- neoplasm can be any size, single or multiple - solid, partially cystic, or largely cystic masses - usually hypo echoic relative to normal thyroid -Calcifications are present in 50-80% of all types of thyroid carcinoma -Inc. vascularity
Medullary Carcinomas
-5% of thyroid cancers -Derived from C-cells -serum calcitonin can be used as a marker -female predominance -sonographic appearance is similar to papillary carcinoma -high incidence of metastatic involvement of lymph nodes have been reported
Hurthle Cell Carcinoma
-Large thyroglobulin epithelial cells -found in both nonneoplastic and neoplastic thyroid lesions -classified as benign adenoma or malignant -account for 3% of thyroid cancers -sonography can't conclusively diagnostic
Sonographic signs malignancy (occurs in what two types of goiters?)
-Malignancy -incomplete/irregular anechoic rims -hypoechogenisity -inc. vascularity (occurs in both endemic and sporadic distributions)
Primary Hyperparathyroidism
-Most common endocrine disorder -Caused by too much PTH -State of increased function of the parathyroid glands -women Characterized by Hypercalcemia, hypercalciuria and low serum levels of phosphate (hypophosphatasia)
What are some characteristics of a benign thyroid nodule?
-a uniform hypoechoic halo -Avascularity -well-defined, regular margins
Scanning Protocol
-accumulation of transverse, longitudinal, and oblique -Longitudinal: carotid artery, lateral image, mid image, mid image with measurements, medial image, possible isthmus -Transverse: superiorly (Mandible) to inferiorly image superior pole, mid pole, mid pole with measurements, inferior pole Make sure you can through the entire thyroid by scanning beyond the borders to avoid missing any pathology
What is the IMA artery?
-arises from the brachiocephalic trunk -ascends in front of the trachea to the lower part of the thyroid gland -Approx 3-10% of the population -appears to compensate for the deficiency or absence of one of the other thyroid vessels
Malignant lesion
-carcinoma rar -Solitary nodules= greater risks for malignancy (risk of malignancy decreases with multiple nodules)
Common masses in the thyroid
-cysts -nodules -Adenomas -Goiters
Thyroid Nodules
-descriptive term -define any abnormal growth that form in the thyroid -4-7% of adults -common in women -inc. with age -inc. dev. with a dec. in iodine intake (you need the right amount of iodine, the usual cause of abnormalities is when it is off)
Etiology of Graves Disease
-females 5:1 -genetics -immune system -stress -environmental factors
What are some typical Symptoms of Graves Disease?
-hyperthyroidism -elevated level of T3 and T4
What is the thyroid? -what does it do? -main function? -what kind of gland is it? -greatest clinical values
-site of synthesis, storage, and controlled secretion of thyroid hormones. -Functions to control the basal metabolic rate (BMR) - largest endocrine gland -Greatest clinical value is in confirming mass locations, differentiating between cystic and solid lesions, and imaging biopsy needle during FNA
Thyroid Cysts
-true cysts are rare -colloid filled -usually benign -15-25% of cystic lesions are solid nodules that degenerating nodule or hemorrhaged -sonographically described as: mixed (hypoechoic and anechoic,completely black/no echoes, because its degenerating) and complexed masses
What are two true cysts?
1. Thyroglassal duct cyst- located midline 2. Branchial cleft cyst- located lateral to the carotids (both differentiating in their location)
Thyroid secretes what 3 hormones?
1. Triiodothyronine (T3) (10%) 2. Thyroxine (T4) (90%) 3. Calcitonin
What percentage of thyroid nodules develop into cysts and why?
15-25% because they are degenerating and hemorrhage
What is the normal size of the adult thyroid gland? (along with thickness, weight, and largest size)
4.0 to 6.0 in length x 1.3 to 1.8 cm in anterior posterior (AP) thickness: 2 cm weighs 15-20 g in adult larger in females
Thyroid Follicle and its structure
= epithelial cells, chemically processes iodine to secrete T3 and T4 -contains colloid, thryoglobular, T3 and T4 -parafollicular cells (c-cells) secrete calcitonin - iodine pump
Nontoxic Nodules/Goiter
=Functioning -not initially associated with hypo/hyperthyroidism -normal lab values -insufficent amount of thyroid hormones -may result from iodine shortage or gland malfunction -varied sizes -end stage can develop into multinodular nodules -can become malignant
Toxic Goiter
=not functioning -hyperthyroid condition resulting from hyperactivity of thyroid gland (TSH) -goiter/nodule becomes a hyper-functioning nodule which means that it is active and produces thyroid hormones -grows from an existing longstanding goiter(over time, non toxic can become toxic)
Anaplastic Carcinoma
Accounts for less than 2% of thyroid cancers -composed of undifferentiated cells -aggressively metastatic -derived from epithelial cells -usually occurs after the age of 50 Risk factors: pre existing thyroid disease both malignant and benign is a major etiologic factor
Acute vs. subacute Thyroiditis
Acute: suppurative thyroiditis is caused by a bacterial infection Subacute: granulomatos thyroiditis (de Quervains disease)( D q va ins) - caused by viral infection of thyroid - pain may be severe - may cause transient hyperthyroidism but in a period of week of months swelling and pain subside and gland functions normally - gland may appear enlarged and hypo echoic with normal decreased vascularity
Where do adenomas develop?
Adenomas develop from a nodule or from thyroid epithelium
Which aggressive form of thyroid cancer has a tendency a compress and destroy the local structures of the neck?
Anaplastic Carcinoma
which cancer is more prevalent to cause asphyxiation and or compression?
Anaplastic carcinoma
Parathyroid Adenoma
Benign lesion Solitary May involve any of the four parathyroid glands Most found in the typical superior and inferior locations Sonographically Appear hypoechoic Homogenous Echogenicity is less than the thyroid gland and may resemble a cyst Is hypervascular
Thyroid plays major roles in
Body metabolism Heart rate growth BP body temp energy production -effects the development and function of the organs throughout the body
Where is calcium stored?
Bones
How does the thyroid gland control so many of the body's functions?
By the secretion of hormones -thyroxine= tetraiodothyronine= T4 -Triiodothyronine= T3 -Calcitonin= parafollicular cells= c-cells
What is the embryonic development of the parathyroid gland?
Development from tissue migration - 4 parathyroid glands ( posterior to thyroid) -possible to have ectopic extras
The Thyroid and Parathyroid are both what type of glands?
Endocrine Glands
Goiter
Enlargement of the thyroid -due to iodine deficiency -due to compensatory hypertrophy and hyperplasia of follicular epithelium caused by derangement that hampers hormone secretion -focal or diffuse thyroid gland enlargement due to iodine deficiency; multiple nodules may be present -may become very large, compressing esophagus and interfering with swallowing, or cause pressure on trachea toxic nontoxic
Second most common thyroid cancers
Follicular Thyroid Carcinoma two types: 1. minimally invasive (encapsulated) 2. Widely invasive (non encapsulated) -female 3:1 -lacks papillary projections -inc. in areas of endemic goiters
which cancer is both mildly and widely invasive?
Follicular carcinoma
How many arteries feed the thyroid?
Four arteries provide a rich blood supply to the thyroid gland - two paired superior thyroid arteries -two paired inferior thyroid arteries
The thyroid gland is host to what?
Host to benign(not harmful), malignant(infectious), autoimmune( disease cause by something natural in the body), and metazoic conditions- all that have overlapping and carried sonographic appearances
Thyroid Negative feedback system
Hypothalamus--> Hypothalamus releases TRH--> Anterior pituitary--> Anterior pituitary releases TSH->Thyroid gland--> Thyroid gland release thyroid follicles T3 and T4 (inc. metabolism, growth and development, etc.) --> (Homeostasis is restored) Increased T3 and T4 concentration in the blood--> (Homeostasis) Normal T3 and T4 concentrations, normal body temperature--> (Homeostasis disturbed) Decreased T3 and T4 concentration in the blood or low body temperature--> Hypothalamus (cycles starts all over)
The most common cause of thyroid disorder world wide?
Iodine deficiency
What is need to release T3 and T4 from the thyroid follicle?
Iodine/ Iodine Metabolism= TSH binds to a receptor= turns on Iodine Pump= Stimulates the cell to synthesize and secret T3 and T4 from within the colloid of the cell
Primary Hyperparathyroidism
Most patients asymptomatic at time of diagnosis with no signs of nephrolithiasis or osteopenia. Primary hyperparathyroidism occurs when increased amounts of PTH produced by adenoma, primary hyperplasia, or (rarely) carcinoma located in parathyroid gland.
What is the system called that regulates T3 and T4?
Negative feedback system- of the hypothalamus-pituitary system
Can nodules becomes adenomas?
No, nodules can't become an adenoma
Are most thyroid cysts true cysts?
No, true epithelium cysts are rare, colloid filled -usually benign -15-25% of cystic lesions are solid nodules
Euthyroid
Normal, the thyroid gland is producing the right amount of thyroid hormone
What is the system called that regulates the production of calcitonin?
PTH- responsible for monitoring the levels of serum calcium- high levels of calcium produce the hormone calcitonin
Sonographic Evaluation
Patient History-("why was a thyroid Sonogram ordered?") Medication, patient presentation, previous studies, fan history Patient Position- supine, hyperextended neck, patients head turned to the opposite side being examined Transducer Selection- 7.5- 15 MHz linear (transverse and longitudinal)
What controls the thyroid gland?
Pituitary gland - through TSH levels
Thyroid regulates function of body organs and adaptions controls such as
Reg. function of body organs: controls growth and development, coordinates reproductive system, digestion and absorption, H2O and electrolytes Adaptions control: stress (fight or flight response), regulates the adaption of change to environment
Other autoimmune diseases associated with Hashimoto's Thyroiditis
Sjogren disease, Lupus, Rheumatoid arthritis, Fibrosing mediastinitis, non- hodgkins
What is the largest muscle in the neck and where is it located?
Sternocleidomastoid muscles -located anterolateral to the thyroid - attaches in the front of the anterior manubrium and is directly superiorly, laterally and posteriorly to attach at the back of the inferior portion of the occipital bone -largely responsible for the head and neck flexion
Strap Muscles
Sternohyoid and Sternohyoid muscles located anterior to the thyroid (+ Omohyoid muscle)
What is stored and located inside the lumen of the thyroid follicle?
T3 and T4
What does TSH do to the thyroid follicle
The TSH that is Free Fasting in blood attaches to Epithelial cells, that turns on Iodine pump to transfer that iodine into cell. Once the Iodine gets into follicle, then you begin synthesize of T3 and T4
Where to the inferior arteries arises from?
The two inferior arteries originate at the thyrocervical trunk of the subclavian artery and supply(ascend) the lower thyroid poles
Where to the superior arteries arises from?
The two paired superior arteries arise from the external carotids and supply(descend) the upper thyroid poles
Where is T3 and T4 stored?
Thyroid follicular epithelial cells (along with colloid and thyroglobulin and free flowing blood)
How is T3 and T4 produced?
Thyroid gland traps Iodine from blood and through a series of chemical reactions. A colloid is a glycoprotein called thyroglobulin. Iodine trapping is the first step in the metabolism of Iodine. The process commences with uptake of Iodine from capillary into follicular cells of the gland by active transport this produces thyroid hormones triiodothyronine (T3) and thyroxine (T4)
Hyperthyroidism is used interchangeably with?
Thyrotoxicosis (too much T3 and T4 outside the normal functioning gland) -both refer to hyperactivity -TSH is increased during primary hyperthyroidism -TSH is decreased during secondary hyperthyroidism
What is TRH?
Thyrotropin- Releasing Hormone
Where are the carotid arteries located in relation to the thyroid?
Transverse: CCA is posterior/lateral border Longitudinal: laterally
Lymphoma
Uncommon -primarily 5% of all thyroid cancers -encompasses a heterogenous group of diseases -can occur as a generalized lymphoma or as a primary lymphoma( non-Hodgkins) -nearly all lymphomas arises from lymphoma raises from lymphocytic Hasimotos thyroiditis -Female to male 4:1 -sonographically large, solid, hypoechoic, compresses/ infiltrate adjacent parenchyma -hypovascular or chaotic vessel distribution and arteriovenous shunts
Are adenomas nodules?
Yes
Parathyroid adenoma
a benign, solid tumor of the parathyroid gland that secretes parathyroid hormone, which results in elevated levels of serum calcium
Thyroid adenoma
a benign, solid tumor of the thyroid gland
Anaplasia
a loss of differentiation of cells that is a characteristic of tumor tissue and occurs in most malignant tumors
Which hormone is more abundant? Which hormone is more potent?
abundant= T4 potent= T3
Graves Disease + characteristics
an autoimmune hyperthyroidism caused by the antibodies that continuously activate thyroid stimulating hormones (TSH) receptors; it is characterized by enlarged thyroid, protrusion of the eyeballs (exophthalmos- accumulation of fat and inflammation with edema aka Ophthalmopathy), a rapid heartbeat, nervous excitability -diffuse toxic goiter -hypermetabolism (hyperthyroidism) -inc. Vascularity -diffusely homogeneous and enlarged glands
Where are the right and left lobes of the thyroid located in relation to the trachea?
anterior/lateral
What is another name for parafollicular cells?
c-cells (produce calcitonin)
What is Nuclear medicine used for? Classified as?
called Nuclear Up-take scan used to determine function of thyroid aka radio iodine scintigraphy examination -classifed as: Hot (hyper functioning/autonomous) Cold (in a not functioning nodule)
Etiology
cause of a condition or a disease
indolent
causing little pain or slow growing
between hot and cold nodules which one has the potential to become malignant?
cold
What is a sporadic goiter?
comes from a normal (euthyoid) population ( the goiter has nothing to do with the environment and iodine levels) -just someone within that person
Benign Nodular thyroid disease
common among adults and the prevalence increases with age -15-25% of solitary thyroid nodules are either cystic or predominantly cystic -sonographically described as a mixed or a complex lesion
What is the pyramidal lobe? What is it a remnant of?
conceal shape, extends from the upper part of the isthmus, up across the thyroid cartilage to the hyoid bone. It is a remnant of the fetal thyroid stalk, or thyroglassal duct - 41.3% of the population -variations occurring most often, arises from the causal portion of the thyroglassal tract, small extending midline upward the isthmus)
Thyroglossal duct cyst
development fluid-filled spaced; congenital anomaly located anterior to trachea extending from the base of the tongue to the isthmus of the thyroid
Hyperparathyroidism
disorder associated with elevated serum calcium level; usually caused by benign parathyroid adenoma
Adenopathy
enlargement of the glands
Cervical Adenopathy
enlargement of the lymph nodes
comet tail artifacts
grey scale ultrasound finding seen when small calcific/crystalline/ highly reflective) - frequent in complex
Anything with the term Adenoma
has the risk to become malignant
What are the variations of the thyroid gland?
heterotopic locations: (occurring at an abnormal place or upon the wrong place of the body) -thyroglossal duct cyst -Anthyrosis (absence of the thyroid) -pyramidal lobe -others: lingual, sublingual, prelaryngeal, substernal thyroids
Hyperechoic
high amplitude/ or density than the surrounding structures (appearing light)
What kind of transducer is used when scanning the thyroid?
high-frequency, high-resolution designed for small parts scanning (linear) -higher frequency= better resolution -lower frequency= better depth of penetration -12 MHz linear array
Parathyroid Hormone -what are parathyroid hormones produced by?
hormone produced by the parathyroid glands that regulate serum calcium and phosphorus -Parathyroid hormone is produced by the chief cells of the gland -PTH is the Important regulator of calcium and phosphorous concentrations -PTH Major target is bones and kidneys by the absorption of calcium in the intestines (GI tract)
Thyroid Inferno
increase in color Doppler vascular flow in the thyroid -overactivity of Graves Disease manifested monographically by inc. vascularity on color doppler
Thyroiditis
inflammation of the thyroid
Fine-Needle Aspiration
invasive-procedure using a small gauge needle to obtain a tissue specimen from a specific lesion -Ultrasound uses a high-frequency, high-resolution transducer to guide in procedures like FNA and alcohol ablation of adenomas of the parathyroid glands
Sporadic Goiter
is the benign development of a goiter in the thyroid gland in euthyroid (normal) population
What is anterior to the trachea?
isthmus
What is the Thyroglassal duct and where is it located?
it is a cylindrical tube and it is located midline
Sternocleidomastoid Muscles
large muscles located anterolateral to the thyroid
Relational anatomy to the thyroid medial anatomy:
larynx, trachea, inferior constrictor of pharynx, esophagus
Hypophosphatasia
low phosphatase level that can be seen with hyperparathyroidism
Papillary Carcinoma
most common form of thyroid cancer -more common in sporadic goiter regions -(2003) 87% of thyroid cancers -due to early detection -women 3:1 -20% have metastatic cervical adenopathy Risk factors: inc. exposure to radiation, high iodine intake, heredity
Hashimoto Thyroiditis (chronic lymphocytic thyroiditis or Hashimoto Disease)
most common inflammatory disease of the thyroid gland (most common cause of thyroiditis); usually occurs in genetically predisposed individuals, often presents in patients with other autoimmune disorders that may be associated with the formation of antibodies against normal thyroid tissue , and often accompanied by marked hyperemia -painless -3/4 of hypothyroidism is this -sonographic appearance changes with time associated with: too much iodine intake, selenium deficiency, smoking, chronic hep C, ages 45-60
Heterotopic/ Ectopic
occurring at an abnormal place or upon the wrong part of the body -"Outside" but still functions
Endemic Goiter other causes?
occurs in a geographic areas where iodine levels in the soil and food are low other causes: Graves Disease, thyroiditis, neoplasm, or cyst
Where is the foramen caecum?
opening at the base of the tongue (foramen= opening)
Primary Hyperparathyroidism
over secretion of parathyroid hormones
Hyperthyroidism -80% of hyperthyroidism is due to? Results from? leads to? Symptoms?
oversecretion of thyroid hormones TSH low, T3 and T4 high -80%= Graves Disease -result from pituitary- thyroid regulatory system failure due to iodine deficiency ( a decrease in TSH due to an elevation in T3 and T4) -leads to hyperplasia and or goiter -symptoms ( dramatically inc. metabolic rate) weight loss, thin hair, inc. app, excessive sweating, Exopthalmos (protruding eyes)
Where can calcitonin be found in the thyroid gland?
parafollicular cells (c-cells) -Calcitonin= decreases the level of calcium by inhibiting bone breakdown
What glands create the balance of calcium in the blood stream?
parathyroid thyroid
Where are the Parathyroid glands located?
posterior to the thyroid (two superior, two inferior) Usually Four glands Can have more Can be absent Can be ectopically placed
Where is the esophagus located?
primarily a midline structure, may be found left of the trachea (trachea is anterior to the esophagus)
What does the term endemic mean?
regularly found among particular people or in a certain area
conditions for secondary hypothyroidism
related to: -pituitary, hypothalamus, medications, congenital disorders, Sheehan syndrome
Structures in relation to the thyroid: -Strap muscles -longus colli muscle -trachea -CCA and IJV
strap muscles are located anterolateral longus colli muscle is seen posteriorly trachea is located midline/ posterior CCA and IJV are posterolateral
Isthmus
thin band of thyroid tissue connecting the right and left lobes
Halo
thin complete or incomplete peripheral hypoechoic to anechoic rim surrounding lesion, is edema of compressed normal thyroid tissue or fibrous capsule of adenoma
Congenital Abnormalities
things we are born with
Microcalcifications
tiny hyperechoic foci that may or may not shadow; sometimes present within a thyroid nodule
toxic vs. nontoxic goiters
toxic= not functioning nontoxic= functioning
Hypothyroidism usually due to? results in? Symptoms?
underactive thyroid hormones (most common occurring thyroid condition) -usually due to iodine deficiency TSH high, T3 and T4 low ( elevation of TSH due to a decrease in T3 and T4) -results in a normal size thyroid/ or a enlarged thyroid Symptoms fatigue, dry skin, weight gain, muscle weakness
What is the etiology of the cystic portion of a thyroid nodule?
usually hemorrhage( escape of blood from a ruptured blood vessel) or is subsequent degeneration of preexisting nodules
Longus Colli Muscles
wedge-shaped muscle posterior to the thyroid lobes -anterior and lateral to the vertebral column -has 3 parts that are inserted into the upper and lower sections of the cervical vertebrae and depending on which parts extends to the T3 of the thoracic vertebra