Anatomy & Pathologyof the Thyroid

Teresa M Bieker, MBA, RT, RDMS, RDCS, RVT

Lead Diagnostic Medical Sonographer

University of Colorado Hospital

Denver Colorado

Objectives

• Anatomy and Pathology of the thyroid and surrounding structures

• Identify suspicious characteristics of thyroid nodules

• Types and occurrences rates of thyroid cancers

Embryology of the Thyroid

Formation of the thyroid begins approximately at the 4th week of gestation

The two lobes are connected by the thyroglossal duct (at the level of the tongue)

By the 7th week, the thyroid should be descended to the level of the trachea

Anatomy of the Thyroid Right and left lobes are located

anterolateral to the trachea & esophagus Right and left lobes are connected midline

by the isthmus Size (adults)

Length: 4-6cm AP: 1.3-1.8cm Isthmus: 4-6mm

Neck Muscles

Strap muscles (anterior) sternohyoid sternothyroid omohyoid

Sternocleidomastoid (lateral) Longus colli (posterior)

Neck Vessels

Thyroid Vessels superior thyroid arteries and veins inferior thyroid arteries and veins

Major Neck vessels carotid artery jugular vein

Function of the Thyroid

Produce, store, secrete thyroid hormones

Thyroid hormones are important for: Proper growth Development Metabolism Body temperature Heart rate/rhythm

Iodine metabolism: converts iodine from food into thyroid hormones

Thyroid Hormones

TSH (Thyroid Stimulating Hormone) T3 (Triiodothyronine) T4 (Thyroxine) Calcitonin Antibodies Thyroglobulin (TG)

Thyroid Hormones

• TSH: – Stimulates the thyroid to produce T4 and

then T3. – Controlled by the pituitary gland

• T4/T3:– Produced by the thryoid

• TSH/T4 work together

Thyroid Hormones• Calcitonin

– Produced by the thryoid– Helps to regulate calcium levels

• Antibodies– Typically present in autoimmune thyroid

diseases (Graves, Hashimoto’s)• TG

– Produced by thyroid tissue– Tumor marker

Indications for Neck Ultrasound• Palpable enlargement• Abnormal thyroid hormone levels• Palpable mass• Swelling in the neck• Asymmetry of the neck• Redness and/or tenderness• Difficulty swallowing• Post thyroidectomy evaluation

Scanning Technique Patient Position

Supine with neck extended Elevating the head 20o in larger

patients may be helpful Neck rotation

Transducer Frequency 7-15 MHz

Image optimization Scanning Planes

Congenital Anomalies Pyramidal lobe

10-40% of patients Arises superiorly from isthmus

Shape variations Missing isthmus “H” shape

Ectopia (rare, follows embryological path) Agenesis

One lobe Complete

Pyramidal lobe

Agenesis of the Right Thyroid

Diffuse Thyroid Pathology

Hyperthyroidism (Grave’s Disease) Hypothyroidism Thyroiditis

Acute Chronic

Hyperthyroidism (Grave’s Disease) Overproduction of thyroid hormone

Low TSH, high T3, T4 Causes

Abnormal hormone production Pituitary tumor Thyroid nodule/neoplasm

Symptoms: Increased metabolism Weight loss, increased appetite Nervous energy Tremors Excessive sweating Palpitations Heat intolerance Fatigue Exophthalmos

Hyperthyroidism (Grave’s Disease)

Sonographic Appearance: Enlarged Heterogeneous Hypervascular

Treatment: Radioactive iodine Medication Surgery

Hypothyroidism Under secretion of hormone production

High TSH, low T3, T4 Causes

Low intake of iodine Thyroid hormone failure Pituitary disease

Symptoms: Weight gain Hair loss Increased tissue around eyes Intellectual and motor slowing Cold intolerance Constipation Deep voice Myxedema (coma, life threatening)

Hypothyroidism

Sonographic appearance Variable in size and echogencity

Treatment Medication

Acute/Subacute Thyroiditis Acute

Rare, caused by bacterial infection Painful, firm, enlarged thyroid, may see

abscess Patients have neck swelling, fever, pain

Subacute (de Quervain’s Disease) Diffuse inflammatory disease Painful enlarged thyroid Thyroid appears large and hypoechoic

Chronic Thyroiditis-Hashimoto’s Autoimmune disease, often resulting in

hypothyroidism Increased risk for papillary thyroid cancer Symptoms

Cold intolerance, weight gain, fatigue Sonographic appearance

Enlarged, hypoechoic, heterogenous thyroid with fibrous strands

May have scalloped edges Multiple lymph nodes “Burned out” thyroid late in disease

Treatment (medication)

Hashimoto’s Thyroiditis (early)

Hashimoto’s Thyroiditis (burn out)

Riedel’s Thyroiditis

• Rare• Thyroid tissue is replaced by dense

fibrous tissue• Thyroid is hard (stone-like) and fixed• Can cause tracheal compression• Can treat with steroids and possible

surgery

Benign Focal Thyroid Pathology

Colloid Adenomas Goiters Cysts

Colloid Nodules• Colloid is product of the thyroid that

consists of thyroglobulin and serves as a storage reservoir for thyroid hormones

• Reservoirs can form within the thyroid and fill with colloid and colloid crystals

• Anechoic with echogenic focus/foci with comet tail artifact

• Overwhelmingly benign

Insert colloid pix

Adenomas Usually benign Single or multiple Normal labs unless functioning Sonographic appearance

Focal with smooth borders May have hypoechoic “halo” May have rim calcification Range in size and echogenicity

Patients are usually asymptomatic

Adenoma

Goiter Thyroid is enlarged (can have neck tightness

difficulty swallowing) Causes:

Iodine deficiency Hereditary Medications

Can be associated with Graves disease Toxic vs Non Toxic Goiter:

Toxic: Nodules are functioning, causing changes in lab values

Non Toxic: non functioning

Goiter

Sonographic appearance Multiple nodules Nodules vary in size and echogenicity Heterogeneous gland

Treatment & Symptoms depend on thyroid size and hormone levels

Goiter

Cysts True cysts are uncommon Cystic appearing lesions are usually

degenerating adenomas or colloid nodules

Sonographic appearance: display cystic characteristics may have internal echoes and irregular walls

Alcohol ablation is a treatment option

Cysts

Malignant Pathology

Papillary Carcinoma Follicular Carcinoma Medullary Carcinoma Huthle Cell Carcinoma Anaplastic Carcinoma (Giant Cell) Lymphoma Metastasis to Thyroid

Papillary Carcinoma

Most common type of thyroid cancer Cause usually unknown, but more common in

females Symptoms:

Palpable nodule Asymptomatic Thyroid hormones can be normal or

abnormal Slow growing, least aggressive thyroid cancer Spreads through lymphatic system

Papillary Carcinoma Sonographic appearance

One or multiple nodules with irregular borders

Typically hypoechoic, but can vary Microcalcifications (strong sign) Increased internal vascularity May see multiple central or lateral

lymph nodes Treatment

Follicular Carcinoma Second most common thyroid cancer More common in females Not aggressive but can metastasize Tends to spread through bloodstream Sonographic appearance

One or multiple nodules with irregular borders Vary in echogenicity, may have calcifications Increased internal vascularity Thick, irregular halo

Treatment

Medullary Carcinoma Often familial More aggressive than papillary or follicular Often secretes calcitonin Likely to metastasize to lymph nodes Sonographic appearance

Hypoechoic mass(s) that may contain multiple calcifications

May also have lymph node/liver metastases Treatment

Hurthle Cell Uncommon Not aggressive but likely to

metastasize (nodes, blood, lungs, bone)

Sonographic appearance is variable Treatment

Anaplastic (Giant cell) Least common, most aggressive, most

lethal Neck is tender, mass is hard and fixed Rapidly growing Invades neck muscles, vessels, trachea Sonographic appearance

large hypoechoic mass Treatment

Lymphoma

• Typically non-Hodgkin’s type• Rapidly growing, hypoechoic, lobulated

mass• Prognosis varies depending on stage

Metastsis to Thyroid Typically from melanoma, breast and

renal cell Primary is typically diagnosed Patients feels neck fullness, palpable

mass Sonographic appearance

Solid, homogeneous, hypoechoic without calcifications

Parathyroid Glands Anatomy Hormones Pathology

Adenomas Hypoparathyroidism Hyperparathyroidism

primary secondary

Parathyroid Anatomy Four parathyroid glands

2 superior 2 inferior (more variable in location)

Normal glands are small 1 x 3 x 5 mm

Function Produce parathyroid hormone which

regulates blood calcium levels

Parathyroid Adenomas

Typically just one gland is affected Sonographic appearance

enlarged round homogeneous and hypoechoic

Treatment

Hypoparathyroidism

Post thyroidectomy complication Clinical diagnosis Symptoms:

Numbness at mouth, then into extremities Seizures Cardiac arrhythmias/arrest

Temporary or chronic Treatment:

Calcium and Vitamin D supplements (IV and oral)

Primary Hyperparathyroidism Usually caused by functioning adenomas High calcium levels during routine lab work

Symptoms: Often asymptomatic Can develop fatigue, depression, weakness Severe symptoms: constipation, confusion, painful

bones, renal stones Sonographic appearance

Enlarged Round Homogeneous and hypoechoic

Treatment

Secondary Hyperparathyroidism Found in patients with chronic renal failure

unable to produce vitamin D leading to decrease in calcium levels. More parathyroid hormone is produced trying to increase calcium levels

Sonographic appearance enlarged parathyroids, often bilateral

Uncommon (due to the success of dialysis)

Secondary Hyperparathyroidism

Salivary Glands

Location Parotid Submandibular Sublingual

Appearance Pathology

Salivary Glands• Parotid

– Anterior to ear, largest gland, triangular• Submandibular

– Deep to mandible• Sublingual

– Under tongue, small, not seen well by ultrasound

• Sonographic appearance– Homogeneous and echogenic

Salivary Gland Pathology

Susceptible to infection and inflammation

Patients can have swelling, pain, fever Ultrasound helpful in identifying

possible fluid collections or abscess

Other Neck Lesions

Thyroglossal Duct Cyst Branchial Cleft Cyst Carotid Body Tumor

Thyroglossal Duct Cyst Congenital anomaly Located midline, anterior to trachea More commonly seen in children Sonographic appearance

Anechoic to hypoechoic Can contain debris or fluid level

Treatment

Branchial Cleft Cyst Fetal remnant Located slightly to the right or left of midline

and anterior to the sternocleidomastoid Sonographic appearance

Anechoic to hypoechoic Can contain debris or fluid level

Treatment

Carotid Body Tumor/Paraganglioma Rare, typically benign, slow growing Usually unilateral, located at carotid

bifurcation, and fed by the ECA Patients feel neck mass or have a

sudden change in blood pressure Sonographic appearance

Round, smooth borders Typically hypervascular

Treatment

Carotid Body Tumor

Thyroid Nodule Summary

Benign Nodules: Wider then tall Cystic Hyper/iso/

hypoechoic Thin halo Well defined Course calfications Peripheral flow

• Malignant Nodules:– Taller then wide– Hypoechoic– Thick, incomplete

halo– Absent halo– Spiculated– Microcalcifications– Internal flow