Chapter 22 Thyroid Flashcards
The thyroid is part of what system?
endocrine system
What is the thyroid function?
it maintains metabolism, growth, and development.
Also, it produces, stores, and secretes thyroid hormones
What are the 3 main thyroid hormones?
T4, T3, Calcitonin
Where is the thyroid located?
Located in the anterorinferior neck at the level of the thyroid cartilage
What connects the two lobes of the thyroid?
isthmus
What is bounded laterally to the thyroid?
Bound laterally by the carotid artery and jugular vein
The size and shape of the thyroid gland varies with what?
gender, age, and body surface area
What small percentage of population has this superior from the isthmus?
pyramidal lobe
What is the size of the thyroid for adults?
Length- 40-60mm (4-6cm)
AP- 20-30mm (2-3cm)
Width- 15-20mm (1.5-2cm)
What is the size of the thyroid for children?
Length- 20-30mm (2-3cm)
AP- 12-15mm (1.2-1.5cm)
Width- 10-15mm (1-1.5cm)
What is the size of the isthmus?
4-6mm
What lies anterolateral to the thyroid?
Muscles- Strap muscles- sternothyroid, omohyoid, and sternohyoid
Muscles- Sternocleidomastoid muscles
What lies posterolateral to the thyroid?
Carotid artery, jugular vein, and vagus nerve
What lies medial to the thyroid?
Larynx
Trachea
Esophagus-may be to the left of midline
Posterior border of each lobe has superior and inferior parathyroid glands
Blood supplies by how many arteries?
4
from where do the two superior thyroid arteries arise from?
Two superior thyroid arteries arise from external carotid artery (ECA) and descend to the upper poles
From where do the two inferior thyroid arteries arise from?
Two inferior thyroid arteries arise from the thyrocervical trunk of the subclavian artery and ascend to the lower thyroid poles
Where do the thyroid veins drain into?
Corresponding veins drain into the internal jugular veins.
what is the mechanism for producing thyroid hormones?
iodine metabolism
How is T3 and T4 produced?
The thyroid traps iodine from the blood and, through chemical reactions produces T3 and T4 (stored in colloid of the gland)
When the body needs thyroid hormone , it is released into the bloodstream by the action of what?
When the body needs thyroid hormone , it is released into the bloodstream by the action of thyrotropin also known as thyroid-stimulating hormone (TSH)
What is TSH produced by?
pituitary gland and hypothalamus
What does calcitonin decrease?
the concentration of calcium in the blood
What does euthyroid mean>
When the thyroid is producing the correct amount of thyroid hormone
This is a normal state
Define hypothyroidism
undersecretion of thyroid hormone
What are the causes of hypothyroidism?
Low intake of iodine (goiter) in the body
Inability of the thyroid to produce adequate amount of the thyroid hormone
A pituitary gland that does not control the thyroid production
Clinical signs and symptoms for hypothyroidism
Myxedema-swelling and thickening of the skin Weight gain* Hair loss* Increased subcutaneous tissue around the eyes Lethargy-no energy, tired* Intellectual and motor slowing Cold intolerance Constipation Deep husky voice*
define hyperthyroidism
oversecretion of thyroid hormone
what are causes of hyperthyroididm?
Occurs when the entire gland is out of control or when a localized neoplasm (adenoma) that causes overproduction of the thyroid hormone
What does hyperthyroidism increase?
dramatically increases metabolic rate
What are the clinical signs for hyperthyroidism?
Weight loss* Increased appetite High amount of nervous energy Tremor Excessive sweating* Heat intolerance* Palpitations* Exophthalmos (Protruding eyes)
What is important to obtain with the patient?
Obtain pertinent patient history
General health
Use of thyroid medication or history of use
Previous imaging of thyroid
Family hx. Of hyperparathyroidism or thyroid cancer
History of radiation or surgery to the neck
What is the most common cause of thyroid disorders?
iodine deficiency
what does iodine deficiency lead to?
goiter formation and hypothyroididm
What are some nodular thyroid diseases?
Nontoxic simple goiter Toxic multinodular goiter Grave’s disease Thyroiditis Benign Lesion Cyst Adenoma
Define goiter
Enlargement of the thyroid gland that is often visible as an anterior protrusion of the neck.
When a goiter enlarges what can happen?
May become very large, compressing the esophagus and interfering with swallowing, or it can put pressure on the trachea
What are some characteristics of a goiter?
May be diffuse and symmetrical or irregular and nodular
What are some causes of goiters?
Graves’ disease
Thyroiditis
Neoplasm
Cyst
Sonographic findings of a goiter?
Enlarged, nodular and appearance may vary
Overall heterogeneous thyroid
Isoechoic to hyperechoic nodules
Thin peripheral halo as a result of perinodular blood vessels and edema
Fibrosis and calcifications may develop
Ultrasound is used to determine the location and characteristics of the masses
describe cysts in thyroid
Cyst-thought to be cystic degeneration of a follicular adenoma
Anechoic-serous or colloid fluid
Echogenic or moving fluid-hemorrhage
describe adenoma
Adenoma-follicular adenoma is benign and characterized by complete fibrous encapsulation.
Adenomas are more common in who?
females
describe adenomas
Range from anechoic to echogenic
Commonly have peripheral halo
Halo may be a result of edema of compressed thyroid tissue or capsule of the adenoma.
describe malignant lesions
Rare
The ultrasound appearance is variable- size, single vs. multiple, solid, largely cystic or complex
The risk of malignancy decreases with multiple nodules
What is an indication for malignancy?
Solitary nodule with cervical adenopathy on the same side suggest malignancy
What is present in thyroid carcimonas 50-80%?
calcifications
what are the types of malignant lesions?
Papillary Follicular Medullary Anaplastic Lymphoma
What is the most common thyroid carcinoma?
papillary carcinoma
How does papillary carcinoma spread through?
spreads through the lympathics
What are ultrasound findings of papillary carcimona?
25% cases have round laminated calcifications
20% will have cervical lymphadenopathy
Ultrasound Findings
90% hypoechoic
Microcalcification with or without shadowing
90% hypervascular
What are the two types of follicular carcinoma?
Two types- minimally invasive and widely invasive
Usually solitary
True or false- follicular carcinoma is more aggressive than papillary
true
how does the follicular carcinoma spread by?
Spreads through bloodstream rather than lymphatics
Ultrasound findings of follicular carcinoma
Irregular margin with thick irregular halo
Nodular enlargement
Tortuous internal blood vessel
Where can mets spread to?
bone, lung, brain, and liver
What accounts for 5% of thyroid cancers?
medullary carcinoma
ultrasound findings of medullary carcinoma
Ultrasound findings
Similar to papillary ca.- hypoechoic
Calcium deposits are often noted
Careful evaluation of the entire neck are and liver to rule out metastases
What does medullary carcinoma have a high incidence in?
High incidence in metastatic involvement of lymph nodes
a characteristics of medullary carcinoma
Often familial- 20% of the time
May be multicentered and/or bilateral in familial cases
What accounts for less than 2% of carcinoma?
anaplastic carcinoma
characteristics of anaplastic carcinoma
Usually occurs after age 50
Hard fixed mass with rapid growth
Growth is locally invasive in surrounding neck structures
It usually causes death by compression and asphyxiation due to invasion of the trachea
ultrasound findings of anaplastic carcinoma
Hypoechoic
Invasion of surrounding muscles and vessels
Lymphoma in the thyroid is usually what type
non-Hodgkin
Lymphoma clinically is ?
rapid growing neck mass
What are preexisting cases for patients with lymphoma?
Many cases patient has preexisting chronic lymphocytic thyroiditis (Hashimoto’s disease) or hypothyroidism
ultrasound findings of lymphoma
Nonvascular Hypoechoic Lobulated Thyroid tissue may be heterogeneous because of associated thyroiditis Can have areas of cystic necrosis
define diffuse thyroid disease
Generally causes diffuse enlargement of the gland without palpable nodules
conditions that cause diffuse enlargement
Graves/ disease
Thyroiditis
Colloid or adenomatous goiter
how is diffuse thyroid disease diagnosis made?
Diagnosis is made on the basis of clinical and lab findings
define thyroiditis
Swelling and tenderness of the thyroid
What is thyroiditis caused by
Caused by infection or related to autoimmune abnormalities
What are types of thyrioditis
Acute suppurative
Subacute (de Quervain’s)
Chronic lymphocytic (Hashimoto’s disease)
What is the most common type of thyroiditis?
hashimotos thyroiditis
what is hashimotos thyroiditis
Characterized by destructive autoimmune disorder, which leads to chronic inflammation of thyroid
Young or middle age female
Painless and diffuse enlargement
ultrasound findings of hashimotos
Coarse and slightly more hypoechoic
Initially homogenous enlargement occurs with nodularity then progresses to inhomogeneous enlargement.
What can hashimotos develop into
hypothyroidism
what is graves disease
More frequently in women over 30 and related to autoimmune disorder
Characterized by thyrotoxicosis and is the most frequent cause of hyperthyroidism
What are findings of graves disease
Findings- hypermetabolism, diffuse toxic goiter, exophthalmos, and cutaneous manifestations
appearance of graves disease
Thyroid gland is diffusely homogeneous and enlarged
What is thyrotoxix crisis or thyroid storm
acute situation with uncontrolled hyperthyroidism-usually extremely vascular
Usually precipitated by infection or surgery
May be life threatening- hyperthermia, tachycardia, heart failure, and delirium
what is the most common number for parathyroid
4 but some have 3-5
parathyroid are most commonly paired how?
Most commonly paired- 2 posterior to superior pole and the other 2 posterior to inferior pole
describe how parathyroid looks like
Flat disk shaped
Echo texture similar to thyroid tissue
Normal size 4mm and not seen on ultrasound
Occasionally a single gland can be seen as a flat hypoechoic mass posterior and adjacent to the thyroid
Glands > 5mm can be seen as an elongated hypoechoic mass between the posterior longus colli and anterior thyroid lobe
What is parathyroid lab data
Calcium sensing organs in the body
Produces parathyroid hormone (PTH) and monitor serum calcium feedback mechanism
Patients with unexplained hypercalcemia are the most common referrals for parathyroid sonography.
what can be done to detect inferior parathyroid glands
have the patient swallow in realtime
What is primary hyperparathyroidism
Increase in function
Women two to three times more likely than men
Particularly common after menopause
what is primary hyperparathyroidism characterized by
Characterized by- hypercalcemia, hypercalcuiria and low serum levels of phosphate (hypophosphatasia)
true or false patients are most asymptomatic at the time of diagnosis for primary hyperparathyroidism
true
what are manifestations for primary hyperparathyriodism
Manifestations are nephrolithiasis and osteopenia
when does primary hyperparathyriodisn occur
Occurs when PTH is increased by adenoma, primary hyperplasia, or, rarely, carcinoma of the parathyroid
characterics of primary hyperplasia
10% of primary hyperparathyroidism cases
Hyperfunction of all parathyroid glands with no apparent cause
Rarely > 1cm
Hyperplasia may or may not involve all glands
what is the most common cause of primary hyperparathyroidism (80%)
adeoma
what is the most common shape of adenoma
Most common shape is oval, hypoechoic
Benign usually
primary hyperparathyroidism carcinoma
Differentiation between adenoma and cancer is difficult
Mets to regional nodes or distant organs, capsular invasion or local recurrence must be present for cancer to be diagnosed
Most- small, irregular, firm mass
define secondary hyperparathyroidism
Chronic hypocalcemia
Usually all four glands are involved
The abnormalities listed below induce PTH secretion leading to secondary hyperparathyroidism
what are the causes of secondary hyperparathyroidism
Renal failure
Vitamin D deficiency (rickets)
Malabsorption syndromes
define thyroglossal duct cyst
Thyroglossal Duct Cyst
congenital midline of neck anterior to trachea.
Oval or spherical masses rarely larger than 2 or 3cm
define bracial cleft cysts
Brachial Cleft Cyst
Usually lateral to thyroid gland
define abscess
Can occur in any location in the neck
Most common low level echoes with irregular walls. Can be anechoic to echogenic
define Lymphadenopathy
Enlargement of lymph nodes or lymph vessels
