slide 3 surgery thyroid

7/29/2019 slide 3 surgery thyroid

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Thyroid diseases


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Thyroid Anatomy

1. Endocrine gland2. Normally extends from ~ C-5

through ~ T-1

3. Highly vascular

4. Weights ~20 - 30 grams


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Thyroid, Detailed Anatomy, continued

5. Pyramidal lobea. present in ~ 33% of population.

b. Extends upward from isthmus

c. anterior to thyroid cartilage


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The Thyroid Gland

Located in theanterior region of

the neck This gland has an

accessory(pyramidal) lobe


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Thyroid, General Information, continued

8. Isthmus crosses trachealcartilages 2-4

9. Base located ~4-5th tracheal cartilage

10. Thyroxin function: regulates basic

metabolism in all cells


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Thyroid Gland, Anterior and Posterior Views

Thyroid Gland: anterior view (left); and posteriorview (right)


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Thyroid, Detailed Anatomy, continued

c. Lobes:1. Attached to cricoid cartilage

by ligaments

2. Medial surface adapted to

larynx and trachea


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Thyroid, Detailed Anatomy, cont

d. Isthmus

1. 1.25 cm x 1.25 cm

2. Crosses @

tracheal rings ~2-4

3. Occasionallyabsent


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Histology

Functional unit of thyroid gland is thethyroid follicle

cuboidal epithelial cells surrounding

colloid filled lumen

active follicles are smaller

responsible for thyroid hormone

synthesis Parafollicular C Cells (Clear cells)

secrete calcitonin

respond to serum ionized calcium levels


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Embryology

Thyroid gland is derived frominvagination of endoderm of firstbranchial pouch near lingual bud

Grows inferiorly around the hyoid toanterior trachea

remnant is thyroglossal duct

Aberrent thyroid tissue can belocated anywhere along thyroglossalduct


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Embryology

Parafollicular Cells are of differentorigin than thyroid follicular cells

these cells originate from

ultimobranchial apparatus near inferiorportion of pharyngeal pouch

ultimobranchial organ seen in lower

vertebrates as a separate organ


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Physiology

Primary function of the thyroid glandis the secretion of thyroid hormones

T4 is primary released hormone

T3 at least 10 times more active

T4 is converted to T3 peripherally

Production of thyroid hormones isregulated in normal gland by thyroidstimulating hormone (TSH) from theanterior pituitary gland


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Physiology

Thyroid Hormone Secretion:

TSH joins follicular cell receptor, then:

cAMP mediates:

active transport of iodide

synthresis of thyroglobulin (TG) by ER

Thyroperoxidase (TPO) mediates:

conversion of iodide to iodine coupling of iodine to tyrosine and TG

(colloid)

Lysosymes release T4/T3


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Ultrasound

Used to establish the size & shape ofthe gland .

May indicate if nodules are single ormultiple.

It will distinguish between cystic &solid lesions. (intrathyroid lesion)


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Radioisotpe scan

Single or multiple nodules .

Over functioning (hot nodules) ornon-functioning (cold nodules)

20% of cold nodules are malignant

Hot nodules .rarely malignant

Hot n Cold n


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FNA

Should be performed in the investigation of all

thyroid nodules.

Distinguish between a solid lesion & a cyst

If the lesion is solid.cells are sent for

cytological examination If the lesion is a cyst .then the fluid can be

removed


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Hypothyroidism - Primary

Autoimmune Diseases are the mostcommon cause of hypothyroidism

Hashimotos Thyroiditis

Graves disease (usuallyhyperthyroidism)

Iatrogenic causes are the next most

common causes Surgery, radioiodine ablation,

inadequate replacement, Li,

Amiodarone, iodide


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Hypothyroidism - Congenital

Cretinism

severe hypothyroidism in the newborn

PE: protuberant abdomen, face, flat

nose, yellow skin, constipation,lethargy, feeding difficulties, hoarse, MR

Endemic: goiter present. Maternal IgG

or maternal antithyroid medications Sporadic: thyroid agenesis (Di George

syndrome most common)


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Treatment

thyroxine

to render the patient euthyroid normal dose 75-150 ug

TSH cheacked every 12-18 months

liothyronine(T3) is an alternative

elderly patient with ischemic heart disease

starting at 25ug & dose every fortnight

(to avoid tachyarrhythmias & cardiac failure)


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Common Signs and Symptoms

of Hyperthyroidism

Nervousness

Irritability

Difficulty Sleeping

Bulging Eyes

Unblinking Stare

Goiter

Rapid Heartbeat

Increased Sweating

Heat Intolerance

Unexplained Weight Loss

Scant Menstrual Periods

Frequent Bowel

Movements

Warm, Moist Palms

Fine Tremor of Fingers

May Include:


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Thyroiditis - Continued Acute Suppurative Thyroiditis

Bacterial infection, usually S. aureus orS. pneumo. Usually preceded bytrauma

Tx: IV abx, I and D if abscess Painful Thyroiditis (de Quervains)

Unknown virus

Painful thyroid following URI Hyperthyroidism followed by

hypothyroidism - lasts 2 month

Tx: beta blockers/thyroxine, supportive


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Thyroiditis, Continued

Postpartum Thyroiditis

Silent thyroiditis of pregnancy andfirst few postpartum months

Associated with Graves disease andother autoimmune diseases

Tx: beta blockers/synthroid as needed

Usually self limiting, but high titers ofantibodies heralds long term disease


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Hashimotos Disease, Cont.

Histology: Askanazy changes-predominant lymphocytes withgerminal centers. Scant follicles

Tx:

Hypothyroid patients: synthroid

Hyperthyroid: antithyroid medications

Surgery reserved for failure ofsuppression or suspicion of lymphoma


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Thyroid Diseases

Medullary Thyroid Cancer

Uncommon

Can run in families

Good cure rate

Intermediate


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slide 3 surgery thyroid

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