22 Thyroid Flashcards
Embryological origin of thyroid
1st and 2nd pharyngeal arches
Origin of superior thyroid artery
First branch off external carotid
Origin of inferior thyroid artery
Of thryocervical trunk
Supplies both the inferior and superior parathryoids
Ima artery
From innominant or aorta
Supplies the thyroid isthmus
1% of patients
Superior and middle thyroid veins drain to:
Internal jugular vein
Inferior thyroid vein drains to:
Innominante vein
Superior laryngeal nerve
Motor to cricothyroid muscle
Runs lateral to thyroid lobes
Runs close to superior thyroid artery
Injury - loss of projection and easy voice fatigability
Recurrent laryngeal nerve
Motor - all of larynx except cricothyroid muscle
Runs posterior to thryoid lobe in tracheoesophageal groove
Can run with inferior thyroid adrtery
Left RLN - around aorta; Left LLN - around innominate artery
Injury - hoarseness; bilateral injury can obstruct airway
Liagment of berry
Posterior medial suspensory ligament close to RLNs
Needs careful dissection
Peroxidases
Link iodine and tyrosine together
Deiodinases
Separates iodine from tyrosine
Most sensitive indicator of thyroid gland function?
TSH
Tubercules of Zuckerland
Most lateral, posterior extension of thyroid tissue
Rotate medially to find RLNs
Leave behind in a subtotal thyroidectomy
Post-thyroidectomy stridor
Incisional hematoma (open neck and remove emergent) Bilateral RLN injury (emergent tracheostomy)
Thyroid storm
Sx: Tachycardia, fever, numbness, irritability, vomiting, diarrhea, HOCF
Undiagnosed Graves’ disease
Precipitants - anxiety, excessive gland palpation, adrenergic stimulants
Tx: B-blockers, PTU, Lugol’s solution, cooling blankets, oxygen, glucose
Wolff-Chaikoff effect
High doses of iodine (Lugol’s solution, potassium iodide) - inhibits TSH action on thyroid and inhibits organic coupling of iodide.
Results in less T3 and T4 release.
Transitory effect.
Best initial test for asymptomatic thryoid nodule?
FNA
Thyroid function tests
Thyroid FNA shows: Follicular cells
Lobectomy (10% CA risk)
Thyroid FNA shows: THyroid cancer
Thyroidectomy or lobectomy
Thyroid FNA shows: Cyst fluid
Drain fluid
If recurs or is bloody - lobectomy
Thyroid FNA shows: collid tissue
Most likely to be a colloid goiter - low chance of malignancy (<1%)
Tx: thyroxine, lobectomy if it enlarges
Thyroid FNA shows: normal thyroid tissue and TFTs are elevated
Solitary toxic nodule
Tx:
- Asymptomatic can monitor
- Symptomatic - PTU and 131I
Thyroid FNA shows: Indeterminant
Get radionuclide study
- Hot nodule - PTU and 131I if symptomatic
- Cold nodule - lobectomy
Goiter
Any abnormal enlargemetn
MCC - iodine deficiency
Operate if airway compression or suspicious nodule
Tx: subtotal or total thyroidectomy
Substernal goiter
Usually secondary - vessels originate from superior and inferior thyroid arteries
Primary - rare, vessles originate from innominate artery
Mediastinal thyroid tissue
Inferior extension of normally placed gland
Lingual thyroid
Thyroid tissue that persists at foramen cecum
Sx: dysphgia, dyspnea, dysphonia
2% malignancy risk
Tx: thryoxine suppression, abolish with I131
Thyroglossal duct cyst
Moves upward with swallowing
Risk for infection and malignancy
Tx: Sistrunk procedure (remove midportion of hyoid bone with thyroglossal duct cyst)
Treatment for young patients, small goiters and mild T3/T4 elevations?
Propylthiouracil
Methimazole
Treatment for pregnant patients?
PTU
PTU (thioamide)
Inhibits peroxidases, inhibits peripheral conversion
AE: aplastic anemia, agranulocytosis
Methimazole
Inhibits peroxidases
AE: creatinism, aplastic anemia, agranulocytosis
Radioactive iodine (131I)
Poor surgical risk or unresponsive to PTU
CI - children, pregnancy
Graves disease
Exophthalmos, pretibial edema, afib, heat intolerance, thirst, increase appetite, weight loss, sweating, palpitations
IgGG antibodies to TSH receptor
Dx: decreased TSH, increased T3/T4; increased 123I uptake, diffusely
Tx: Thioamides, 131I, thyroidectomy
Operating on graves disease?
Indication - suspicious nodule, non-compliant patient, recurrence after medical therapy, children, pregnancy (not controlled with PTU)
Preop prep - PTU until euthyroid, B-blocker, Lugol’s solution (decrease friability and vascularity)
Op - bilateral subtotal or total thyroidectomy
Toxic multinodular goiter
Women, >50yo
Sx: tachycardia, wt loss, insomnia, airway compromise (can be precipitated by contrast dye)
Hyperplasia secondary to chornic low-grade TSH stimulation
Tx: Surgery (subtotal or total thyroidectomy), 131I if elderly and frail
Single toxic nodule
Women, younger, usually >3cm if symptomatic, functions autonomously
Dx: Thyroid scan (hot nodule)
Tx: Thioamides and 131I, lobectomy if medical tx infeffective
Hashimoto’s
Hyopthyroidism
Enlarge gland, painless, chronic thyroiditis
History of childhood XRT
Humeral and cell-mediated autoimmune disease (microsomal and thyroglobulin antibodies)
Tx: Thyroxine, partial thyroidectomy if continues to grow, nodules appear or compression symptoms
Bacterial thyroiditis
Contiguous spread from URI
normal thyroid function test, fever, dysphagia, tenderness
Tx:
- ABX
- Lobectomy (R/O cancer for unilateral swelling)
- Total thyroidectomy (persistent inflammation)
DeQuervain’s Thyroiditis
Hyperthyroid > hypothyroid
Viral URI precursor
Elevated ESR
Tx: Steroids, ASA
- Lobectomy (R/O cancer for unilateral swelling)
- Total thyroidectomy (persistent inflammation)
Riedel’s fibrous stomra
Woody, fibrous compartment - invasive Need biopsy to R/O CA/lymphoma Compression symptoms Tx: - Steroids, thyroxine - Isthmectomy or trachesotyom for airway symptoms - RLNs at great risk if resected
Thyroid nodule - worrisome for malignancy
Solid Solitary Cold Slow growing Hard Male Age >50yo PRevious neck XRT MEN IIa or IIb
Follicular adenoma
Colloid, embryonal, fetal
No increased cancer risk
Lobectomy to prove it is an adenoma
Papillary thyroid carcinoma
Best prognosis
Childhood XRT
Lymphatic spread first - but prognosis based on local invasion
Pathology - psammoma bodies, oprhan annie nuclei
Treatment of papillary thyroid carcinoma - minimal/incidental (<1cm)
Lobectomy
Treatment of papillary thyroid carcinoma - Bilateral lesion, multicentricity, history of XRT, positive margins or tumors >1cm
Total thyroidectomy
Treatment of papillary thyroid carcinoma - clinically positive cervical ndoes
Ipsilateral MRND
Treatment of papillary thyroid carcinoma - extrathyroidal tissue involvement
Ipsilateral MRND
Treatment of papillary thyroid carcinoma - metastatic disease, residual local disease, positive LN or capsular invasion
131I
4-6 weeks after surgery
When do you use XRT in treatment of papillary thyroid carcinoma?
Unresectable disease not responsive to 131I
Enlarged lateral neck lymph node with normal-appearing thyroid tissue?
Papillary thyroid CA with lymphatic spread
Total thyroidectomy and MRND
131I 4-6 weeks after surgery
Follicular thyroid carcinoma
Hematogenous spread - bone
FNA shows follicular cells
Tx: Lobectomy
- Adenoma/folliclar cell hyperplasia - done
- Follicular CA - total thyroidectomy and 131I (if >1cm or extrathyroidal)
Medullary thyroid carcinoma
MEN IIa or IIb Parafollicular C cells Path - amyloid deposition Screen for hyperPTH and Pheo Lymphatic spread Tx: total thyroidectomy with central neck node dissection
What is the first manifestation of MEN IIa or IIb?
Diarrhea
Where does medullary thyroid cancer spread to?
Lung, liver, bones
Prophylaxtic thyroidectomy and central node dissection for MEN - when?
MEN IIa - 6yo
MEN IIb - 2yo
Hurthle cell carcinoma
Most benign
Bone and lung mets
Tx: Total thyroidectomy and MRND for clinically positive nodes
Anaplastic thyroid cancer
Most aggressive
Tx: total thyroidectom, palliative thyroidectomy or chemo-XRT
XRT effective for:
Papillary, follicular, medullary and Hurthle cell thyroid CA
131I effective for:
Papillary and follicular thyroid CA only
Indications for 131I
Recurrent CA
Primary inoperable tumors due to invasion
Tumars >1cm or extrathyroidal disease (extra-capsular invasion, nodal spread or mets)
I131 AE
Sialoadenitis GI symptoms Infertility BM suppression Parathyroid dysfunction Leukemia
Gene Mutations: Papillary Thyroid Carcinoma
BRAF
Gene Mutations: Medullary Thyroid Carcinoma
RET-1
Gene Mutations: Anaplastic Thyroid Carcinoma
p53
Gene Mutations: Follicular thyroid carcinoma
PAX8/PPAR-gamma
