Anatomy & Pathology of 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) Sternocleidomastoid (lateral) sternohyoid sternothyroid omohyoid Sternocleidomastoid (lateral) Longus colli (posterior)

Neck Vessels Thyroid Vessels Major Neck 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: T4/T3: TSH/T4 work together 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 Antibodies TG 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 Shape variations 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 Causes Symptoms: 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 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 Normal glands are small 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 Appearance Pathology Parotid Submandibular Sublingual Appearance Pathology

Salivary Glands Parotid Submandibular Sublingual 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