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