Thyroid Flashcards
Pharyngeal pouches
1st and 2nd
Superior thyroid artery
1st branch of external carotid artery; gives off superior laryngeal artery
Inferior thyroid artery
off thyrocervical trunk off subclavian; supplies sup & inf parathyroids; RLN usually adjacent to inferior thyroid a
Superior & middle thyroid veins
drain into internal jugular vein
Inferior thyroid vein
drains into innominate & brachiocephalic veins
Recurrent laryngeal nerve
motor to all of larynx except cricothyroid muscle; run in tracheoesophageal groove
Left RLN
loops around aorta
Right RLN
loops around right subclavian or innominate artery
RLN injury
hoarseness; b/l injury can obstruct airway
Superior laryngeal nerve
motor to cricothyroid muscle; runs lateral to thyroid lobes
Superior laryngeal nerve injury
loss of projection and easy voice fatigability (opera singers)
Tubercles of Zuckerkandl
most lateral, posterior extension of thyroid tissue rotate medially to find RLNs; this portion is left behind with subtotal thyroidectomy because of proximity to RLNs
Ligament of Berry
posterior medial suspensory ligament; primary point of fixation of thyroid to surrounding structures; close to RLNs
Thyrotropin-releasing factor
released from hypothalamus; acts on anterior pituitary gland & causes release of TSH; release is controlled by T3 and T4 through negative feedback loop
Thyroid stimulating hormone
release from anterior pituitary gland; acts on thyroid to release T3 and T4 through mechanism that involves increase cAMP; release is controlled by T3 and T4 through negative feedback loop; most sensitive indicator of gland function
Thyroglobulin
stores T3 and T4 in colloid
Plasma T4:T3 ratio
15:1; T3 more active form (tyrosine + iodine); most T3 produced in periphery by T4 to T3 conversion by peroxidases (link or separate tyrosine & iodine)
Thyroid-binding globulin
thyroid hormone transport; T3 & T4 also bind albumin
Parafollicular C cells
produce calcitonin (inhibit calcium absorption by osteoclasts; decrease peripheral serum Ca levels)
Thyroxine treatment
TSH levels should fall to 50%; osteoporosis long term side effect
Thyroid storm
tachy, fever, numbness, v/d, hight output cardiac failure (MCC of death); most common after surgery in pt with undx Graves’ disease
Thyroid storm tx
B-blockers, PTU, Lugol’s solution, cooling blankets, O2, glucose, fluid
Wolff-Chaikoff Effect
very effective for pts in thyroid storm; give high doses of iodine (Lugol’s solution, KI) which inhibits TSH action on thyroid & inhibits organic coupling of iodide; results in less T3 & T4 release
Asymptomatic Thyroid Nodule
85% are benign; F>M
1st thyroid function tests: if elevated give thyroxine; nodule should regress in 6 months; if not elevated FNA
FNA thyroid nodule
determinant in 75-90%
follicular cells: total or lobectomy (5-10% malignancy)
thyroid ca: total or lobectomy
cyst fluid: drain; if recurs then surgery
colloid tissue: likely goiter; low chance of malignancy (
Radionuclide study
hot nodule: thyroxine for 6 months, if size does not decrease then surgery
cold nodule: total or lobectomy (more likely malignant than hot)
Goiter
any abnormal enlargement; most common cause is iodine deficiency; tx with iodine replacement
Nontoxic colloid goiter
diffuse enlargement w/o evidence of functional abnormality; tx: try to suppress with thyroxine; Iodine-131 (may be ineffective); subtotal thyroidectomy or lobectomy if medical tx fails
Substernal goiter
usually secondary → vessels originate from superior and inferior thyroid arteries
primary → rare; vessels originate from innominate artery; tx: try to suppress with thyroxine; Iodine-131 (may be ineffective); subtotal thyroidectomy or lobectomy if medical tx fails
Mediastinal thyroid tissue
most likely from acquired disease with inferior extensions of normally placed gland
Lingual thyroid
thyroid tissue that persists in area of foramen cecum at base of tongue
Sxs: dysphagia, dyspnea, dysphonia
2% malignancy risk
Tx: thyroxine suppression; abolish with Iodine-131 or resection if it is enlarged or suggestive of cancer, or if it does not shrink after medical tx
Thyroglossal duct cyst
classically moves upward with swallowing
susceptible to infection & may be premalignant
tx: resection; need to take midportion or all of hyoid bone along with thyroglossal duct cyst (Sistrunk procedure)
Graves’ disease
MCC of hyperthyroidism (80%); caused by IgG antibodies to TSH receptor; decrease TSH, increase T3 & T4; tx with thioamides (70% recurrence), RAI (10% recurrence), subtotal thyroide (10% recurrence) or total thyroid with thyroxine replacement if medical tx fails
Graves’ disease and surgery
medical therapy usually manages hyperthyroidism; unusual have to operate on these patients unless in setting of suspicious nodule
Pre op prep → PTU or methimazole until euthyroid, β-blocker 1 week before surgery, Lugol’s solution for 10-15 days to decrease friability & vascularity (start only after euthyroid)
Indications for surgery in Graves’ disease
noncompliant pt, recurrence after medical therapy, children, pregnant women not controlled with medical therapy, or concomitant suspicious thyroid nodule
Toxic Multinodular Goiter
MCC of thyroid enlargement; women; age > 50, normal thyroid fx tests; cardiac symptoms, weight loss, insomnia, airway compromise; symptoms can be precipitated by contrast dyes; caused by hyperplasia 2/2 chronic low-grade TSH stimulation
Tx: RAI & thioamides; subtotal thyroidectomy if medical tx ineffective; unusual have to operate on these pts unless in setting of suspicious nodule
Hashimoto’s disease
MCC of hypothyroidism in adults; enlarged gland, painless, chronic thyroiditis; women; hx of childhood xRT; can cause thyrotoxicosis in acute early stage; caused by both humeral & cell-mediated autoimmune disease (microsomal & thyroglobulin antibodies); goiter 2/2 lack of organification of trapped iodide inside gland; path shows a lymphocytic infiltrate; Tx: thyroxine 1st line; partial thyroidectomy if continues to grow despite thyroxine, if nodules appear or compression symptoms occur; frequently no surgery is necessary for Hashimoto’s disease
Bacterial Thyroiditis
usually 2/2 contiguous spread; normal thyroid function tests, fever, dysphagia, tenderness; upper respiratory tract infection (URI) symptoms most common precursor (staph/strep); Tx: antibiotics; may need lobectomy to r/o cancer in pts with unilateral swelling & tenderness; may need total thyroidectomy for persistent inflammation
De Quervain’s Thyroiditis
can be associated with hyperthyroidism initially; viral URI, tender thyroid, sore throat, mass, weakness, fatigue; more common in women; elevated ESR; Tx: steroids & ASA; may need lobectomy to r/o cancer in pts with unilateral swelling & tenderness; may need total thyroidectomy for persistent inflammation
Riedel’s Fibrous Struma (rare)
woody, fibrous component that can involve adjacent strap muscles & carotid sheath; can resemble thyroid CA or lymphoma (need biopsy); disease frequently results in hypothyroidism & compression symptoms; associated with sclerosing cholangitis, fibrotic diseases, methysergide treatment, and retroperitoneal fibrosis; Tx: steroids & thyroxine; may need isthmectomy or tracheostomy; if resection needed, watch for RLNs
Follicular adenomas
colloid, embryonal, fetal; no increase in cancer risk; still need lobectomy to prove its adenoma
Papillary thyroid carcinoma
most common (80-90%) thyroid ca; least aggressive, slow growing, has best prognosis; young adults, women, children; childhood XRT; lung mets most common; Path psammoma bodies (calcium) & orphan annie nuclei; lymphatic spread 1st but is not prognostic
Papillary thyroid ca TX
minimal / incidental ( 1cm; clinically + cervical nodes → need ipsilateral MRND; extrathyroidal tissue involvement → need ipsilateral MRND;
metastatic disease, residual local disease, + lymph nodes, or capsular invasion → RAI 6 weeks post op;
XRT only for unresectable disease not responsive to RAI
Enlarged lateral neck LN that shows normal thyroid tissue
papillary thyroid CA with lymphatic spread; tx with total thyroid & MRND
Follicular Thyroid Carcinoma
hematogenous spread → bone most common; 50% have metastatic disease at time of presentation; more aggressive than papillary; older adults 50-60s, women; FNA shows just follicular cells → 10% chance of malignancy; need thyroidectomy
Follicular Thyroid Ca TX
lobectomy → if pathology shows adenoma or follicular cell hyperplasia, nothing else needed;
if follicular CA → total thyroidectomy for lesion > 1cm or extrathyroidal disease;
clinically positive cervical nodes → need ipsilateral MRND;
extrathyroidal tissue involvement → need ipsilateral MRND;
pts with lesion > 1cm or extrathyroidal disease or capsular invasion → RAI 6 weeks post op;
if microinvasive (
Medullary Thyroid Carcinoma
can be assoc with MEN IIa or IIb (RET protooncogene);
usually 1st manifestation of MEN IIa and IIb → screen for hyperparathyroidism & pheochromocytoma;
tumor arises from parafollicular C cells (which secrete calcitonin);
C-cell hyperplasia considered premalignant; Pathology → shows amyloid deposition;
Gastrin can be used to test for medullary thyroid CA → causes increase in calcitonin;
elevated calcitonin can cause flushing and diarrhea;
most have involved nodes at time of dx;
early mets → lung, liver, bone
Medullary Thyroid Carcinoma TX
total thyroidectomy with central neck node dissection;
MRND if pt has clinically + nodes (b/l MRND if both lobes have tumor) or if extrathyroidal disease present;
prophylactic thyroidectomy in MEN IIa or IIb patients before 5 yo;
liver & bone mets prevent attempt at cure;
XRT may be useful for unresectable local & distant metastatic disease;
may be useful to monitor calcitonin levels for disease recurrence;
more aggressive than follicular & papillary CA;
50% 5 year survival rate; prognosis based on presence of regional & distant mets
Hurthle cell carcinoma
most are benign (adenoma); presents in older pts; early nodal spread if malignant; mets go to bone and lung; Tx: total thyroidectomy; MRND for clinically + nodes
Anaplastic Thyroid Cancer
elderly patients with long-standing goiters; most aggressive thyroid ca; rapidly lethal (0% 5 year survival rate); usually beyond surgical management by dx; Tx: total thyroidectomy for compressive symptoms or give palliative chemo or XRT
