Thyroid gland Flashcards
Function of the thyroid gland
- Maintains body metabolism
- Maintains growth
- Maintains development
Why are ultrsound the most sensitive modality to evaluate the thyroid gland
- It can detect thyroid lesions
- it can accurately calculate the dimensions of the thyroid gland
- It can identify the structures and vascularity
- It evaluates diffuse changes to the thyroid parenchyma
- Helps to differentiate between thyroid nodules, and cervical masses
Where is the thyroid located
Anteroinferior at the level of the thyroid cartilage
How many lobes in the thyroid
Two
What connects the two lobes of the thyroid
Isthmus
What are the anterior muscles at the thyroid
Strap muscles and sternocleidomastoid muscle
What are the three strap muscles
- Sternohyoid muscle
- Omohyoid muscle
- Sternothyroid muscle
What are the posterior structures of the thyroid and neck
- CCA
- JV
- Vagus nerve
What is the normal length of the thyroid in an adult
4 - 6 cm
What is the normal height of the thyroid gland in adult
1.3 - 1.8 cm
What is the normal width of thyroid gland in adult
1.5 - 2.0 cm
What is the normal length of the thyroid in children
2 -3 cm
What is the normal height of thyroid gland in children
0.2 -1.2 cm
What is the normal width of the thyroid gland in children
1.0 - 1.5 cm
What is the length, height and widht measurement of the parathyroid in an adult
5-7 mm
1-2 mm
3-4 mm
What are the three hormones released by thyroid
- Triidothyronine (T3)
- Thyroxine (T4)
- Calcitonin
The pathway of the hormones
- Hypothalamus releases thyrotropin releasing hormone
- TRH triggers pituitary gland to release thyroid stimulating hormone
- TSH Stimulates the thyroid to release T3 and T4
What gland secretes parathyroid hormone
Parathyroid gland
What is the function of the parathyroid hormone
Maintains homeostasis of blood calcium concentration by promoting calcium absorption into the blood preventing hypoglycemia.
Why a thyroid ultrasound
When there is a palpable thyroid nodules or multinodular goiter
Patient that are of high risk for thyroid malignancy due to radiation exposure and who are in their reproductive years.
In women between ages of 40-44 and in men between ages of 70- 74. Patients with palpable cervical adenopathy suspicious of malignancy
What should you look for in a thyroid ultrasound
If the mass is palpable
If the mass is within o4 adjacent to the thyroid
If the tumor is confined to the thyroid
Is the cervical lymphnodes involved
After operation is there residual or recurrent tumor in the thyroid bed or is there metastases to the lymphnodes in the neck.
What is the normal appearance of the thyroid on ultrasound
Uniformly
What are variants of the thyroid gland
Pyramidal lobe
Absence of isthmus
Assemetry
Absence of lateral lobes
The three composition of the nodule is
Solid
Cystic
Complex
What is the echogenisty of the nodule
Hyperechoic
Hypoechoic
Isoechoic
Markedly hypoechoic
How does the margins of the nodule appear
Well defined and regular
Ill defined, blurred, irregular
What is the measurement of the nodule
Is it taller than wide
Malignant thyroid nodules
- Hyoechoic
- Micro or interrupted rim calcification
- Irregular margins
- Absence of halo or incomplete halo
- Increased intranodular flow
- Height is greater than width
- Significant increase in size over time
- Invasion of anterior strap muscles
- Presence of abnormal cervical lymphadenopath.
Benign thyroid lesions
- Pure cystic nodule
- Hyperechoic
- Halo sign or smooth margin
- Spongiform nodule
- Uninterrupted eggshell calcifications
- Absent or peripheral vascularity.
- Significant decrease in size over time
- Multiple coalescent modules without normal intervening parenchyma
- Normal small reactive cervical nodes
What is a goiter
It’s the enlargement of the thyroid gland due to any cause
What are the two types of goiters
Toxic goiter
Non toxic goiter
What is a toxic goiter
A hyperthyroid condition resulting from hyperactivity of the thyroid gland
What is a non toxic goiter
Diffuse thyroid enlargement not resulting of inflammation, neoplasm, hypo- or hyperthyroidism.
The thyroid is enlarged but the thyroid levels are normal.
What are the sonographic findings of a goiter
- Isochoic compared to normal thyroid tissue
- As it enlarges it becomes more isoechoic
- A well defined halo surrounding nodules
- There is colloid component of cystic elements
- Focal scarring and ischemia, necrosis and cyst formation
- Fibrosis or calcifications
What is hyperplasia
The enlargement of an organ or tissue caused by an increase in the reproduction rate of its cells.
Thyroid hyperplasia
Caused by an iodine deficiency.
Results from anything that lessons the intrthyroidal iodine levels
The sonographic finding of a cyst in thyroid
Purely anechoic areas containg serous or colloid fluid
What is an adenoma in thyroid
A benign thyroid neoplasm that is characterized by complete fibrous encapsulation
What are the sonographic features of a thyroid adenoma
- Peripheral halo that appears anechoic to completely hyperechoic
- Predominantly cystic or mixed cystic and solid lesions
- Isoechoic or predominantly anechoic
- Homogenous or heterogenous
- Increased peripheral blood flow patterns on colour doppler or within
What suggest malignancy in the thyroid
A solitary nodule with cervical adenopathy at the same side
What is the most common malignancy of the thyroid
Papillary carcinoma
What are the risk factors of papillary carcinoma
Females
History of exposure to radiation in childhood
Family history
Obesity
What are the sonographic appearance of papillary carcinoma
- Hypoechoic lesion
- Irregular outline
- Microcalcifications ( small punctate hyperechoic foci)
- Hypervascularity
- Cervical lymphonode metastases
Follicular carcinoma
Second most frequent malignancy of the thyroid
What is the stage of invasiveness of an encapsulated follicular carcinoma
Minimally invasive
What is the stage of invasiveness of a non capsulated follicular carcinoma
Widely invasive as there can be invasion of the blood vessels
What organs does follicular carcinoma metastasis to
Bone
Brain
Lung
Liver
What are the risk factors of follicular carcinoma
Females between ages of (40-60)
Radiation exposure
Iodine deficiency
Pre existing thyroid disease
What are the sonographic findings of follicular carcinoma
Hypoechoic
Irregular margins with thick irregular halo
Nodular enlargement
Tortuous internal blood flow
Modullary carcinoma
A familial neoplasm derived from parafollicular C cells and secretes calcium
What are the sonographic features of medullary carcinoma
Hypoechoic mass
Calcium deposits
Increased vascularity
Anaplastic thyroid carcinoma
A rare aggressive thyroid cancer composed of undifferentiated follicular cells with epitheloid and or spindle cell features
Risk factors of anaplastic carcinoma
Elderly patients
Usually above 50 years
What are the sonographic findings of anaplastic carcinoma
Large hypoechoic mass
Ill defined
Calcifications
Invasion of surrounding soft tissue and vessels
Thyroid lymphoma
Non Hodgkins type
Presents as a rapidly growing painless mass
What are the symptoms of thyroid lymphoma
Obstructive symptoms such as
Dyspnea
Dysphasia
What are the risk factors of lymphoma
Females older than 60
History of chronic lymphocytic disease
Subclinical or overt hypothyroidism
What are the sonogrphic features of thyroid lymphoma
Hypoechoic
Lobulated/ nodular mass
Non vascular
Ill defined
Heterogenous
Large areas of cystic necrosis
Encasement of adjacent vessels
What is acute supportive thyroiditis
A rare inflammatory disease caused by a bacterial infection in immunocompramised patients and children
The presentation of acute supportive thyroiditis
Pain
Firmness
Tenderness
Redness
Swelling
Fever
Dysphagia
Difficulty moving neck
Ultrasound features of acute supportive thyroiditis
Perithyroidial soft tissue involvement
Increased vascularity
Heterogenous ecotecture
Lymphnodes
Hypoechoic
Absess formstion
What is subacute granulomatous thyroiditis (de Quervains disease)
A spontaneously remitting inflammatory disease following a viral infection such as hepatitis B/C, mumps, cytomegalovirus, adenonvirus, measels, influenza
What is the presentation of De Quervains disease
Painful swelling in lower neck
Fever
Lethargy
Gradually/ fairly abrupt onset of pain
Can cause transient hypothyroidism
Sonographic features of deep Quervain disease
Hypoechoic mass
Ill defined mass
Decreased vascularity
Sometimes involvement of contralateral lobes
What is chronic lymphocytic thyroiditis (Hashimotos disease)
The most common thyroiditis that is characterized by a destructive autoimmune disorder which leads to chronic inflammation of the thyroid
How does Hashimotos disease present
Painless
Diffusely enlarged gland
Young middle age females
Sonographic features of Hashimotos disease
Acute phase
Small hypoechoic nodules
Ill defined margins
Origin in anterior portion of isthmus and thyroid
Sonographic features of Hashimotos disease
Subacute
Infiltration proceeds to whole gland
Hypervascular
Sonographic features of Hashimotos disease
Chronic
Enlarged Slightly
Lobulated / lobular outline
Atrophied gland small
What is Graves disease
An autoimmune disorder caused by hyperthyroidism
Risk factors of Graves disease
Females over 30
What are the characteristics of Graves disease
Thyrotoxicosis
Hypermetabolism
Diffuse toxic goiter
Exophthalmus
Cutaneous manifistations
Hyperthyroidism
What are the sonographic features of Graves disease
Enlarged
Hypoechoic
Inhomogenous
Hypervascularity
What is the function of the parathyroid gland
Calsium sensing organ
What happens when there is a decrease in the serum calcium levels
A decrease or drop in the serum calsiumn levels Stimulates the parathyroid gland to secrete parathyroid hormone. The parathyroid hormone acts one the bone, kidneys and instine to enhance calcium absorption.
What transducer is used to scan the thyroid and parathyroid
High frequency transducer (7.5 -15 Mhz)
What is primary hyperparathyroidism
A condition where there is an increase function of the parathyroid gland, to much production of hormones that leads to a loss of bone tissue
Risk factors of primary hyperparathyroisdism
Women
2-3 times more likely to develop
Hyperthyroidism
What are the characteristics of primary hyperparathyroisdism
Hypercalcemia
Hypercalcuria
Low serum levels of phosphate
What conditions causes primary parathyroidysm
Ademonas
Primary hyperplasia
Causes increase amount of pth
Parathyroid ademona
Benign tumor of parathyroid gland and most common cause of primary hyperparathyroisdism
Sonographic features of parathyroid adenoma
- Oval shape
- Homogenous
- Hypoechoic solid
- Usually smaller than 3cm
- Larger addnomas measure greater than 5 cm in length
- Encapsulated with discrete border
- Hypervascular
Parathyroid carcinoma
A rare small irregular mass.
What is important to the diagnostic process of parathyroid carcinoma
Metastases to the regional nodes, distant organs capsules invasion or local occurrence must be seen
What are the sonogrphic features of parathyroid carcinoma
Larger than ademona (>3cm)
Lobular contour
Heterogenous internal architecture
Internal cystic components
Absence of suspicious vascularity
What is secondary hyperparathyroisdism
Chronic hypercalcemia that is caused by renal failure, vitamin D deficiency (Rickets), or malabsorption syndromes.
What happens in secondary hyperparathyroisdism
The abnormalities induces PTH secretion that leads to hypercalcemia.
What are two examples of developmental cyst in the midline of the neck?
Thyroglossal duct cyst
Brachial cleft cyst
What is a thyroglossal cyst
A congenital anomaly that appears at the midline of the neck anterior to the trachea.
What is a brachial c,eft cyst
A cystic formation usually located laterL to thyroid gland
