Module 1: Thyroid Anatomy/Pathology

What is the frequency range of high resolution probes?

7-18 MHz

Are transvaginal and transrectal probes considered high frequency?

Yes

What additional tool(s) can be used to assist visualization of the dead zone during high resolution scanning?

Stand-off pads, gel baths, compound imaging

What is the common thickness of a stand off pad?

1-2 cm

Name the largest endocrine gland that produces hormones.

Thyroid

Define endocrine and exocrine.

Endocrine: ductless, secretes directly into bloodstream

Exocrine: secretes through ducts

Name the structures that have endocrine and exocrine functions.

Pancreas, testicles, ovaries

What is the function of the thyroid gland?

Synthesize, store, secrete-hormones to regulate cell metabolism

Name the hormones the thyroid produces.

•Thyroxine

•Triiodothyronine

•Calcitonin

Which is the primary hormone?

Thyroxine

Which hormone inhibits bone resorption?

Calcitonin

Which hormone is T3?

Triiodothyronine

Which hormone is T4?

Thyroxine

What is necessary to produce T3 and T4?

Iodine

Define TSH

Thyroid stimulating hormone

What is another name for TSH?

Thyrotropin

What produces TSH?

Anterior pituitary gland

Secretion of the thyroid hormones is controlled by?

Hypothalamus and pituitary gland

Calcitonin is secreted by?

Parafollicular cells of the thyroid

Define TRF

Thyrotropin releasing factor

What is another name for TRF?

Thyrotropin releasing hormone

TRF is produced by?

Hypothalamus

What regulated TSH production?

TRF

What regulates TRF?

BMI (basal metabolic rate)

Hypothalamus secretes _______.

TRF

Anterior pituitary secretes______.

TSH

Thyroid then produces _______ and _______.

T3 and T4

When the pituitary senses there’s enough ______and _____, it stops secreting _______.

T3 and T4, TSH

What is the most commonly used blood test to determine thyroid function?

Serum TSH

Define TFT

Thyroid function tests

What is the normal range of serum TSH?

Normal range: 0.5 – 4.7 U/ml

What are the components of the thyroid gland?

Right lobe, left lobe, isthmus

The isthmus lies ______ to the trachea.

Anterior

The right and left lobes are _______ inferiorly and _______ superiorly.

Wider, thinner

Name the arteries that supply blood to the thyroid.  

Superior thyroid artery, Inferior thyroid artery

The ___________ artery is the first branch off the external carotid artery.

Superior thyroid

Describe pyramidal lobe.

Congenital anomaly associated with an additional thyroid lobe.

Where is the pyramidal lobe located?

Upward from the isthmus, left of midline

Name the vessels used as landmarks when imaging the thyroid. Where are they located relative to the thyroid?

•Common carotid arteries (right/left), Internal jugular vein (right/left).

•Both lateral to the thyroid gland.

Name the muscles used as landmarks when imaging the thyroid. Where are they located relative to the thyroid gland?

•Sternocleidomastoid (SCM) muscle, strap muscle, longis collimuscle

•SCM-anterior/lateral to gland

•Strap-anterior/lateral to the gland

•Longis colli-posterior to the gland

Name the images acquired in the transverse plane.

Superior pole, mid pole, inferior pole

Name the images acquired in the sagittal (long axis) plane.

Lateral, mid, medial

What measurements are acquired in the transverse plane?

Width

What measurements are acquired in the long axis plane?

Length, AP (anterior/posterior)

The isthmus is imaged in what imaging plane?

Transverse

What measurement is acquired of the isthmus?

AP

What are the normal size ranges of the following:

•Right/left thyroid lobe:

•Isthmus

•Long: 4-6 cm, AP: 1.3-1.8 cm, width 1.5-2 cm 

•4-6 mm (< 10 mm)

Describe the characteristics of a non-toxic goiter.

Enlarged gland, normal TFT’s

Describe the characteristics of a toxic goiter.

Patient symptomatic, abnormal TFT’s, enlarged or atrophic (small) gland

True or false? Thyroid nodules are:

•Extremely common

•Often malignant

•More common in Males

•More common with exposure to ionizing radiation

•True

•False

•False

•True

What is the most common thyroid mass?

Adenoma

What is another name for adenoma?

Colloid nodules

Name the most common type of adenoma.

Benign follicular

Describe the sonographic appearance of an adenoma.

•Solid masses, variable in size

•May be solitary or numerable

•May appear: hyperechoic, isoechoic, hypoechoic

•Peripheral hypoechoic halo from fibrous tissue encapsulating the adenoma

•Peripheral color Doppler flow

•Cystic components (representing cystic degeneration)

Of the sonographic characteristics, which is most unique to adenoma?

•Peripheral hypoechoic halo from fibrous tissue encapsulating the adenoma

Define MNG.

Mutlinodular goiter

What is MNG the result of?

Multiple adenomas developing over a period of time

Define hyperthyroidism.

Hyperthyroidism-overactive thyroid gland

Define hypothyroidism.

Hypothyroidism-underactive thyroid gland

Define thyrotoxicosis.

Hyperthyroidism caused by too much thyroid hormone, results in an accelerated metabolism

Name 3 common hyperthyroid conditions.

Grave’s disease, toxic adenoma, toxic MNG

Describe the clinical presentation of hyperthyroidism.

•Fatigue with inability to rest

•Trembling hands

•Weight loss with increase in appetite

•Inability to tolerate heat

•Increased sweating

•Increase in bowel movements

•Protruding eyeballs (exophthalmos)

•Skin rash on front of legs

•Staring gaze

•Tachycardia

•Very light menstrual periods

Define exophthalmos

Protruding eyeballs

Define tachycardia

Fast heart rate

Define Grave’s disease

•Diffuse toxic goiter

•Most common form of thyrotoxicosis

•Autoimmune disease

Who and what age group is Grave’s disease most prevalent in?

Females, ages 20-40

What will the lab results show in a patient with Grave’s disease?

Decrease TSH, increase T3 and T4

A tell tale sign of a person with Grave’s disease is:

Exophthalmos

What will the radionuclide (iodine uptake) test show in a patient with Grave’s disease?

Increased uptake (increased activity)

What is the sonographic appearance in a patient Grave’s disease?

Diffusely enlarged, heterogeneous, hypoechoic gland. Hypervascular

Describe thyroid inferno.

Hypervascularity detected with color Doppler in a patient with Grave’s disease.

Which condition is more severe, a patient with Grave’s disease or hyperthyroidism with MNG?

Grave’s disease

What will the lab results show in a patient with hyperthyroidism with MNG compared to Grave’s disease.

Elevated T3 and T4, but not as severely elevated as seen in with Grave’s disease.

Describe toxic adenoma.

Single hyperfunctioning adenoma

What will the radionuclide (iodine uptake) test show in a patient with a toxic adenoma.

Thyroid uptake “hot nodule“

What is the treatment of a patient with hyperthyroidism.

•Antithyroid medication: PTU and methimazole

•Radioactive iodine treatment: I-131 dose given orally via capsule

•Surgical removal: depending on severity

Define thyrotoxic crisis.

Acute thyrotoxicosis

What is another name for thyrotoxic crisis?

Thyroid storm

True or false? Thyroxic crisis is:

•A medical emergency

•Life threatening

•Can occur after thyroid surgery

•May occur after a stressful disorder or illness.

•True

•True

•True

•True

What are the symptoms of thyrotoxic crisis?

•hypermetabolism

•high fever (104 or higher)

• flushing/sweating

•marked tachycardia

•HBP

•N/V/D

•heart failure

•restlessness

•abdominal pain

•delirium and coma

•heart failure and shock lead to death

What is the treatment of thyrotoxic crisis?

•requires immediate management in ICU

•Propranolol (Inderal) given by IV for arrhythmias

•Block production of hormones with PTU

Describe a nontoxic goiter

Goiter not assoc. with hyperthyroidism

What is the TSH level in a patient with a nontoxic goiter?

Normal

Who and what age group is hypothyroidism most prevalent in?

Females, ages 40-50

What will the lab results show in a patient with hypothyroidism?

Elevated TSH, decrease T3 and T4

What are the symptoms of hypothyroidism?

•Fatigue

•Weight gain

•Constipation

•Dry, brittle hair

•Facial edema

•Slow heart rate

Describe primary hypothyroidism.

Permanent destruction of the thyroid from radiation injury or autoimmune disorder

Describe secondary hypothyroidism.

Results form insufficient TSH stimulation

What is the treatment for hypothyroidism?

•Dependent upon T4 levels

•Usually daily thyroid hormone pill

•Meds: synthetic version of T4: (Synthroid, levothyroxine)

•Follow up blood tests to assess T4 levels

True or false? Hypothyroidism is:

•Reversible if treated

•Life threatening of untreated

•True

•True

Define thyroiditis.

Inflammation of the thyroid

What are the categories of thyroiditis?

Acute, subacute, chronic

What is the clinical presentation of a patient with thyroiditis?

Enlarged, tender thyroid gland

Describe acute suppurative thyroiditis

Inflammatory process resulting in an enlarged thyroid gland

What causes acute suppurative thyroiditis?

Bacteria

Is acute suppurative thyroiditis common?

No

What is the sonographic appearance of suppurative thyroiditis?

•Thyroid appears nodular and irregular

•May detect an abscess

•Inflammatory nodes often present

Describe subacute granulomatous thyroiditis.

Inflammatory process causing an enlarged gland.

What is another name for subacute granulomatous thyroiditis?

De Quervain’s disease

What causes subacute granulomatous thyroiditis.

Viral infection