5. ENT Thyroid Gland 2014A
-
Upload
liw-estavillo -
Category
Documents
-
view
218 -
download
0
Transcript of 5. ENT Thyroid Gland 2014A
-
8/17/2019 5. ENT Thyroid Gland 2014A
1/7
1 of 7 |Page Guevara, Guiang, Harris, Hwang; Andrade (editor)
September 19, 2012
Thyroid land
Dr. Lago
OUTLINE
1. History and Introduction
2. Anatomy of the Thyroid Gland
3.
Physiology of the Thyroid Gland
4. Diffuse Thyroid Disease
a. Goiter
b. Hypothyroidism
c.
Hyperthyroidism
5. Evaluation of an Ant. Neck mass
6. Thyroid Carcinoma
HISTORY AND INTRODUCTION
Thyroid gland is an endocrine (ductless) gland
First described by Thomas Wharton in 1656 (also discovered the
submandibular gland)
Secretes substance that lubricates the trachea
Cosmetic
Chemical substance is Thyroxine
o Stimulates O2 consumption of most cells of the body
o Helps regulate lipid and carbohydrate metabolism
o Necessary for growth and maturation
Essential for life
o Absence – poor resistance to cold temperature, mental and
physical slowing. In children, mental retardation/dwarfism
o Excess – body wasting (metabolic acceleration resulting in rapid
consumption of body energy and substrates), nervousness,
tachycardia, tremors, excess heat production
ANATOMY OF THE THYROID GLAND
[2013B]
Composed of 2 lobes connected by the isthmus at the level of the 2nd
and 3rd
tracheal rings (sites of tracheostomy)
o Isthmus of the thyroid gland covers the first few tracheal rings [Boies]
o Thyroid lobes rest on the lateral tracheal wall and may even extend up
onto the thyroid alae [Boies]
Located on the anterolateral portion of the trachea, just below the larynx
o Thyroid gland is located below the cricoid cartilage
Located underneath the anterior muscles of the neck:
o Sternohyoid – most anterior
o Sternothyroid
Thyrohyoid (technically does not pass over the thyroid)
Situated in the muscular triangle of the neck
o Boundaries
Hyoid bone
Omohyoid
Sternocleidomastoid
[Boies]
A normal thyroid gland is normally not palpable
o Palpable mass in the midline compartment of the neck (between the
sternocleidomastoid muscles and overlying the larynx and upper
trachea) that move up and down with swallowing represent thyroidabnormality
o Firm, discrete nodules are more likely to contain malignancy
o Abnormalities of vocal cord function or the presence of palpable lymph
nodes suggest malignancy
HISTOLOGY
Follicular Cells
o Simple cuboidal epithelium surrounding a colloid-filled lumen
o
Acini are filled with pink-staining proteinaceous material
(colloid)
Thyroid cell functions:
o Collect and transport iodine
o Synthesize thyroglobulin and secrete into the colloid
o Remove the thyroid hormones from the thyroglobulin secreting
them into the circulation
BLOOD SUPPLY[2013B]
Superior Thyroid Artery (from the ECA) supplies the upper pole of the gland
Inferior Thyroid Artery (from the thyrocervical branch of the Subclavian
Artery)
VENOUS DRAINAGE[2013B]
Superior, Inferior, and Middle Thyroid veins
LYMPHATIC DRAINAGE[2013B]
Risk for metastasis into the:
o Central Jugular Nodes (Levels 2, 3, and 4)
o Pretracheal Nodes
o Paratracheal Nodes
NERVOUS SUPPLY
Superior Laryngeal Nerve is in close proximity to the superior thyroid a.
ligate at the area proximal to the thyroid to avoid hitting the nerve [2013B].
Injury can lead to low-frequency vocal range and inability to sing higher
notes [Probst]
-
8/17/2019 5. ENT Thyroid Gland 2014A
2/7
2 of 7 |Page Guevara, Guiang, Harris, Hwang; Andrade (editor)
Recurrent Laryngeal Nerve branch of the vagus nerve that passes alongside
the trachea. Injury may cause paralysis of the true vocal cords [2013B]
resulting to hoarseness [Probst]
PARATHYROID GLANDS
[2013B] Located at the back of the thyroid gland at the superior pole and middle
portion.
4 in total 2 on each side
Yellowish in color resembling fat on dissection
Accidental resection leads to hypocalcemia tetanus
May be implanted in other tissues such as the SCM
EMBROYOLOGY
First seen as a ventral midline diverticulum of the floor of the pharynx just
caudal to the junction of the 1st
and 2nd
branchial arches at the site known as
the foramen cecum [Boies]
o Day 24: median epithelial thickening appears in the floor of the
ectodermal pharyngeal gut, dorsal to the future tuberculum impar
[Probst]
Thyroid migrates caudally along a tract that passes ventral to the body of thehyoid, then curves underneath it and downward to the level of the cricoids
cartilage [Boies]
o End of 7th
week: Thyroid gland reaches pre-tracheal position and
thyroglossal duct obliterated or resorbed [Probst]
THYROGLOSSAL DUCT CYST
Vestigial remnants of thyroglossal duct tract [Boies] due to incomplete
obliteration or resorption of the thyroglossal duct [Probst]
Usually tense, firm, midline swelling [Probst] found anywhere between the
base of the tongue and superior border of the thyroid gland that elevates
with swallowing and slide upward when tongue is protruded [Boies]
75% are manifested before 5 years of age and most are diagnosed before 12
months [Probst]
Papillary carcinoma has been reported within thyroglossal duct cysts [Boies],
but malignant transformation is rare [Probst]
Treatment:o Antibiotic therapy (to treat any inflammation/infection) [Boies]
o Complete excision of cyst and thyroglossal duct tract wi th removal of the
central portion of the hyoid bone to prevent recurrence [Boies]
PHYSIOLOGY OF THE THYROID GLAND
THYROTROPIN RELEASING HORMONE (TRH)
Produced by the hypothalamus
Release is pulsatile, circadian (9pm-12am) [2013B]
Travels through the portal venous system to the thyrotropic
cells of the adenohypophysis (anterior pituitary)
Stimulates production and release of thyrotropin (TSH)
Down-regulated by T4
THYROID STIMULATING HORMONE (TSH)
Produced by the adenohypophysis
Travels through the portal venous system to cavernous sinus, body
Stimulates several processes
o Synthesis and release of T3, T4
o Growth of the thyroid gland
Up-regulated by TRH
Down-regulated by T4, T3
THYROID HORMONES
Regulated by the hypothalamic-pituitary gland axis [2013B]
Majority of circulating hormone is T4
o T4 – 98.5%
o T3 – 1.5%
Total hormone load is influenced by serum binding proteins
o Thyroid binding globulin (TBG) – 70%
o Albumin – 15%
o Transthyretin – 10%
Regulation of thyroid hormone production is based on the free
component of thyroid hormone
THYROID HORMONE SYNTHESIS
IODINE – raw material essential for thyroid hormone synthesis
T4 and T3o Synthesized in the colloid by iodination and condensation of
tyrosine molecules bound to TG
Thyroglobulin (TG)
o Synthesized in the thyroid cells
o Excreted into the colloid by cell extrusion (exocytosis) of
granules that also contain an enzyme – thyroid peroxidise
o Hormones remain bound to TG until these are secreted
Iodide iodine (active form) iodine + tyrosine MIT and DIT T3
(MIT+DIT) and T4 (DIT + DIT) binds with thyroglobulin stored within
follicle lumen [2013B]
When secreted
o Colloid is engulfed or ingested by the thyroid cells
o Peptide bonds are hydrolyzed
o
Free T4, T3 are released into the capillarieso Enzyme splitting of the thyroxine from TGB by lysosomes and
endosomes TGB released back into cells and T3 and T4 into the blood
[2013B]
FUNCTION OF THE THYROID HORMONES
Increase sensitivity of target tissues to catecholamines
Promote:
o Lipolysis
o Glycogenolysis
o Gluconeogenesis
Metabolism
o INCREASED:
-
8/17/2019 5. ENT Thyroid Gland 2014A
3/7
3 of 7 |Page Guevara, Guiang, Harris, Hwang; Andrade (editor)
Sensitivity to catecholamines
Basal metabolic rate
Carbohydrate, protein and lipid metabolism
o Normal growth: Increased bone turnover
Normal development
o Especially CNS development (fetal brain and skeletal
maturation)
Regulation of:
- Synaptogenesis
-
Neuronal Integration- Myelination
- Cell Migration
Endocrine system:
o INCREASE in serum GLUCOSE
o DECREASE in serum CHOLESTEROL
CVS:
o Inotropic effects (increase CO)
o Chronotropic effects (increase HR)
Reproduction: Fertility requires normal thyroid function
GIT: Stimulates gut motility
DIFFUSE THYROID DISEASE[Boies]
May be due to:
o Goiter
o Thyroiditis
Inflammatory lesions of the thyroid
Tenderness
Signs and symptoms of inflammation
o Hyperthyroidism
o Grave’s disease
o Advanced carcinoma
GOITER[2013B]
General term for enlargement of the thyroid gland
Not a disease
Can be NODULAR or DIFFUSE
HYPOTHYROIDISM HYPERTHYROIDISM
Puffy Skin
Sluggishness, lowered vitality
Weight GAIN
COLD intolerance
Insomnia
Muscle pain and spasm
Bradycardia
Decreased Libido
Brittle Nails
Profuse sweating
Irritability
Weight LOSS
HEAT intolerance (abnormally
high temperature)
Muscle pain and weakness
Tachycardia
High BP
Exophthalmia – if uncontrolled
Hypothyroidism – reduction in the rate of oxidative energy-releasing
reactions within the body cells
Hyperthyroidism – increase in metabolic rate
Most of these conditions are medically treated [2013B]
CRETINISM
Manifestation of hypothyroidism in children which may result in
mental retardation, dwarfism, permanent sexual immaturity anddeafness [2013B]
TREATMENT
Hyperthyroidism
o Partial removal or by partial radiation (destruction of the gland)decrease the levels of hormone release [2013B]
o Several drugs that inhibit thyroid activity (lifetime management) [Boies]
EVALUATION OF ANTERIOR NECK MASS
[2013B]
Most common reason for consult: anterior neck mass
Decide on either medical or surgical treatment
o Hyperthyroid/Hypothyroid usually treated medically
o
Euthyroid may be medically treated or surgically managed ENTs – Surgical treatment
Endocrinologists – Clinical/Medical treatment
Most have clinically evident signs and symptoms, some look normal
(subclinical variants); Subclinical – may not exhibit symptoms
Hyperthyroid Hypothyroid
Euthyroid
First do hormone testing. If found to be hypothyroid/hyperthyroid treat
medically. If euthyroid evaluate and do thyroid scan. If it is a warm nodule,
then it is most likely benign and so do suppression. If it is a cold nodule there is
high probability of being malignant so do a thyroid ultrasound and do FNAB if
necessary [2013B]
THYROID EVALUATION
*Pituitary Hypo/Hyperthyroidism = Primary Hypo/Hyperthyroidism↑ / ↓ – refer to endo; Euthyroid – work-up (poss. malignancy or surgery)
TSH
Why requested?
o Suspicion of hyperthyroidism/hypothyroidism
o Presence of goiter or nodules
o Monitor response to therapy
o Screening for thyroid dysfunction in certain risk groups (previous
thyroid surgery, DM, history of neck irradiation)
Best assessment of the integrity of Hypothalamic-Pituitary-Thyroid
axis, due to improvements in assays
o Above 0.5 mu/ml – Hyperthyroidism
o Below 0.3 mu/ml – Hyperthyroidism
o
Normal Range: 0.3-0.5 mu/ml Patients with abnormal results are referred to endocrinologists [2013B]
ENTs only manage patients with normal TSH [2013B]
FREE T3 AND T4
Gives an accurate reflection of thyroid hormone production [2013B]
FT4 is more commonly used because it also reflects FT3 levels (TBG common
binding site) [2013B]
Free T4 (FT4) – measures concentration of free thyroxine which is
the only biologically active fraction in serum
Bound thyroxine does not have an effect on pituitary TSH secretion
o Free thyroxine is the only one that has reflex effect on TSH
secretion
TSH
INCREASED
Serum FT4
Increased
PituitaryHypothyroidism
Decreased
Hypothyroidism
DECREASED
Serum FT4
Increased
Hyperthyroidism
Decreased
PituitaryHyperthyroidism
NORMAL
Euthyroid
-
8/17/2019 5. ENT Thyroid Gland 2014A
4/7
4 of 7 |Page Guevara, Guiang, Harris, Hwang; Andrade (editor)
Free T4 is not affected by changes in concentration of binding
proteins, thus conditions like pregnancy, estrogen or androgen
therapy does not affect FT4 levels
TOTAL T3/T4
T3 measures concentration of triiodothyronine in the serum
T4 measures concentration of thyroxine
Test measures both bound and unbound forms
Bounded therefore no direct correlation with metabolic state
Can be affected by changes in the levels of the thyroid binding
globulins, albumin levels. Conditions such as use of contraceptive
pills, acute liver disease will increase binding proteins
RADIOACTIVE IODINE UPTAKE (RAIU)
Measurement of iodine uptake by the thyroid gland from the
extracellular pool over a set period of time
Useful in indicating hyperthyroid states
THYROGLOBULIN
10% normal individuals
15-30% CA patients
Not reliable [2013B]; Best for follow-up on CA after thyroidectomy
Determines remnant thyroid cells after thyroidectomy [2013B]
THYROID SCINTIGRAPHY/THYROID SCAN
Radionuclide imaging of the thyroid
One of the earliest procedures developed in nuclear medicine
Not preferred for work-up of neck mass because test takes a lot of
preparation (radioactive tracer) and is only available in certain
institutions
Uptake studies involve the measurement of the amount of tracers
extracted by the thyroid at specific times
o Concentrated in the thyroid gland which allows visualization of
the gland
The most commonly used radioactive tracers are isotopes of iodine
(I-123, I-131) and technetium pertechnetate (Tc99-m)
o Of the three, technetium pertechnetate can be used with
children because of its short imaging time and less radiationexposure
o Radioactive iodine is administered orally and reaches the
follicular lumen in 20-30 minutes
I-131 has a half-life of 8 days compared to I-123 which has a
half-life of 13 hours
- Higher particulate emission on the gland
- Stays in the body for a longer period of time
Alternative is Tc99-m with a half-life of only 6 hours
- Low particulate emission - Short imaging time and lessened exposure to radiation [2013B]
- Good for children
Is read either as hot (increased uptake) or cold (decreased uptake) nodules
depending on the thyroid gland uptake of the tracer [2013B]
Suspected thyroid nodule
Thyroid scan
“ HOT” “COLD” Multinodules
nodules nodules
Hormone Suppression Ultrasonography Signs of Clinically
Malignancy Benign
Biopsy
Approx. 80-85% are “cold” with 14-22% of them malignant whichneeds surgical treatment [2013B]
5% are “hot” with a 2cm, chances are it will not change in sizeo If ineffective or signs of malignancy appear, then surgery is necessary
[Boies]
10-15% are warm
Scan is 89-93% sensitive but only 5% specific
Indications:
1.
Identification of functional solitary nodules when initial serumthyrotropin is decreased
2. If FNAB findings show "follicular" neoplasm or "suspicious"
results, the finding of a “hot” nodule may decrease the risk of
malignancy
3.
Detecting neck metastasis
ULTRASOUND
Ultrasound – sound is reflected back
Test is easily accessible, so preferably used for work-up of neck mass
Can detect small nodules (
-
8/17/2019 5. ENT Thyroid Gland 2014A
5/7
5 of 7 |Page Guevara, Guiang, Harris, Hwang; Andrade (editor)
o Non-diagnostic fine needle aspirate (as an adjunct for repeat
FNAB)
UTZ
Cystic Solid
FNAB
Malignant Suspicious Benign
FINE NEEDLE ASPIRATION BIOPSY (FNAB)
The single most helpful test to establish the nature of a solitary
nodule (benign or malignant? what kind of malignancy? )
o Gauge 20-25 needle with local anesthetic used (BUT Sir
personally uses a 23 gauge needle without local anesthesia) 10cc, 23 gauge needle – mass is punctured and aspirated to about 4-
5mm pressure [2013B]
o 4-5 separate skin punctures into the nodule to obtain an
adequate specimen for examination
o Must have an experienced cytopathologist
o Extremely safe and inexpensive
o Large "core" needle biopsy (gauge 18,19,21) [2013B]
Increased complication, size limitation, andadditional info vs. FNAB
Not used by Doc: he says that large bore needles tend to
aspirate blood (bloody tap)
Accuracy rates range from 50-90% with a low false positive (90%
4 RECOGNIZED CATEGORIES FOR FNAB
1.
Malignant
2.
Benign
3. Suspicious
4.
Insufficient
RESULTS THAT WARRANTS A SUSPICIOUS LABEL
1.
Hurthle Cell Neoplasm
2.
Follicular variant of papillary carcinoma
3. Low-grade papillary carcinoma
4. Hashimoto's disease
MANAGEMENT ALGORITHM ACCORDING TO FNAB RESULTS
BENIGN
o Is unpredictable therefore needs close observation
o Repeat FNAB after 6-24 months
o Thyroid suppression benefits in five separate studies given at
doses ranging from 100-200μg proved to be not significant in
shrinking nodules especially those >2cm in size [2013B]
MALIGNANT
o Is more straightforward for the predictive value for a positive
FNAB is close to 100% and the specificity is 100%
o Surgery is warranted
SUSPICIOUS
o Includes follicular and Hurthle cell neoplasm
o Limiting factor of FNAB
o Malignancy rate accounts for only 10-20%
o Surgical management is indicatedo Look for poor clinical indicators, if there are presence of poor indicators
it is more likely malignant [2013B] and warrants surgery if malignant Age (60)
Gender (Male)
Prior Radiation
Family History
Pain
Compressive or invasive features
Cervical metastasis
Size (>4cm)
Rapid Growth
INSUFFICIENT
o Requires a repeat FNAB under ultrasound guidance
THYROID SUPPRESSION
1.
Administer Levothyroxine 2. Maintain TSH levels at
-
8/17/2019 5. ENT Thyroid Gland 2014A
6/7
6 of 7 |Page Guevara, Guiang, Harris, Hwang; Andrade (editor)
o Orphan Annie Sign: prominent nucleoli
Peak incidence – 3rd decade of life
Female to Male ratio 3:1
Propensity to spread to lymph nodes in 30-50% of patients
o Lymph node metastasis has no effect on survival
o Presence of lymph nodes may indicate papillary carcinoma
Late metastasis to lungs and bones
Multicentricity seen in 30-60% of patients (higher rate seen in
irradiated patients) – Do not remove just one lobe, remove other lobes[2013B]
Favorable prognosis
5 year survival rate: 90-95%
Occult, incidental thyroid CA (50 years old
Death from papillary CA depends on:
o Age >50 years
o Tumor size and grade
o Initial extent of disease
PATTERNS OF LATERAL NECK METASTASIS IN PAPILLARY CA
Level 1 14%
Level II 52%
Level III 57%
Level IV 41%
Level V 21%
Most metastasis found within the deep cervical lymph nodes
Levels II-V are most commonly involved so selective neck
dissections(SND) II, III, IV, and V is the treatments of choice
Location of Positive Nodes # of Cases
Middle Jugular 85
Lower Jugular 67
Upper Jugular 50
Posterior Cervical 22
Superior Mediastinum 7
Submandibular 4
Haagensen CD et al 1972
FOLLICULAR CARCINOMA
Occur in older patients, typically age 40-60 years
Female to male ratio probably nearly equal
Propensity for angioinvasion and hematogenous spread
Lymph node metastasis are not a prominent feature and only occur
after angioinvasion is seen
Distant metastasis to lungs and bones seen in 50-65% of patients,
and are detected and treated by radioactive iodine I-131 following
total thyroidectomy
Categories:
a. Low-grade: encapsulated, well-differentiated
b. High-grade: angioinvasive and Hurthle Cell CA
10-year survival rate 30-85% depending on tumor grade and
category, BUT NOT on tumor size (Avg = 70%)
Differentiate from follicular adenoma by capsular, vascular, or
stromal invasion. Differentiation is difficult by frozen section and
impossible by FNAB
These tumors concentrate Iodine I-131 quite well, but may lose thischaracteristic with older patients resulting in a worse prognosis
TREATMENT OF DIFFERENTIATED THYROID CARCINOMAS
Controversy involves extent of necessary thyroid resection and
degree of lymph node dissection
o Papillary CA – total thyroidectomy + LN dissection
o Follicular CA – total thyroidectomy
Some data suggest similar survival with total thyroidectomy vs.
ipsilateral thyroid lobectomy and isthmectomy
Treat all patients with papillary or follicular CA with exogenous
thyroid hormone or lifelong TSH suppression. Serum TSH levels
should be nearly undetectable, but toxicity should be avoided
TOTAL THYROIDECTOMY
Treatment for multicentric disease (30-80%)
Probable lower recurrence rate Use Iodine I-131 and thyroglobulin post-operatively
Low incidence of recurrent nerve paresis/hypoparathyroidism
THYROID LOBECTOMY
Avoid hypoparathyroidism and bilateral recurrent nerve injury
Reliance on similar survival data
Difficult, if not impossible, to use Iodine I-131 post-operatively to
treat local and/or distant metastasis fol lowing ablation with Iodine I-
131
-
8/17/2019 5. ENT Thyroid Gland 2014A
7/7
7 of 7 |Page Guevara, Guiang, Harris, Hwang; Andrade (editor)
RADIOACTIVE IODINE THERAPY
Relies on the thyroid tissue’s affinity for iodine uptake in treating
residual or metastatic disease
May give large dose of Iodine I-131 and spare surrounding non-
thyroid tissue from injury
PRIMARY use is in patients following total thyroidectomy
Indicated in ALL patients with LN or distant metastasis
Maybe used selectively in patients with Thyroid CA confined to the
thyroid gland following total thyroidectomy
Discontinue all exogenous thyroid hormone for 3-4 weeks and
confirm preparation by elevated serum TSH
EXTERNAL IRRADIATION
Appears useful only in selected locally invasive thyroid CA (usually
aggressive follicular tumors) and anaplastic CA
CHEMOTHERAPY
Has limited to no usefulness at present
MEDULLARY THYROID CARCINOMA (MTC)
Originally described by Hazard and associates in 1959
Solid histologic pattern with amyloid in its stroma and calcification
seen
In 1967, MTC discovered in association with calcitonin-secreting
parafollicular C cells of neural crest origin (ultimobranchial body) in
the thyroid gland
Elevated levels of serum calcitonin are usually present in MTC and
form a reliable marker for the presence of occult MTC in familial
cases and recurrent MTC in previously treated patients
LN metastasis, detected in 50% of patients, have an adverse effect
on survival and are treated with modified radical neck dissection Systemic metastasis is not responsive to radiation and MTC does not
concentrate Iodine I-131. The usefulness of chemotherapy
(Adriamycin and Cisplatin) is limited
Diarrhea, increased intestinal motility, and elevated calcitonin may
be the first sign of recurrent MTC
ANAPLASTIC CARCINOMA
Uncommon thyroid malignancy affecting older patients
May arise from a well-differentiated thyroid CA
80% of patients have a history of a long standing goiter with sudden
rapid growth, hoarseness, dysphagia, and airway compromise
Tracheal invasion and/or bilateral recurrent nerve paralysis can
be seen
Poor prognosis, usually results in 100% death when diagnosed , with
mean life expectancy of 6-9 months
Death occurs from local invasion of vital cervical structures and
airway compression
Surgical excision is rarely possible without sacrificing essential
cervical structures, but tissue diagnosis is needed for differentiating
it from a lymphoma. Usually do not operate anymore
Tracheostomy and total thyroidectomy are both extremely difficult
External radiation may temporarily control the local effects of
the malignancy
Limited effect from systemic chemotherapy (Adriamycin);
No hormonal manipulation known
References:
2013B Trans, Recording, Lecture, Probst, Boies