Thyroid Flashcards
Embryologic origin of thyroid?
Endodermal cells of foramen cecum
What may persist during descent of thyroid tissue
pyramidal lobe
If the thyroglossal duct doesn’t close what can happen
Thyroglossal duct cyst
What are the C cells origin?
4th pharyngeal pouch
Neural crest tissue
What is the blood supply of the thyroid gland?
Superior thyroid
Inferior thyroid
What is the anatomic location of the superior thyroid artery?
1st branch of external carotid, runs with superior laryngeal nerve.
What is the anatomic location of the inferior thyroid artery?
Branch off thyrocervical trunk, runs with recurrent laryngeal nerve
Provides blood supply to all 4 parathyroid glands
50% of the time passes ant, 50% passes post to recurrent laryngeal
What provides blood supply to all 4 parathyroid glands
Inferior thyroid artery
What is the anatomic location of the thyroid IMA?
Rises off of inominate
5% of people
Venous drainage of thyroid gland?
Superior/Middle Drain into internal jugular
Inferior drains into inominate(bracheocephalic)
Hyperthyroidism tx?
1st medical therapy
PTU, Methimazole: Agranulocytosis, aplastic anemia
PTU okay for pregnancy
Methimazole causes cretinism in pregnancy
Graves Disease pathophys?
Autoimmune dz caused by Ab to TSH -> hyperthyroid
What does graves look like on scintigraphy?
Diffuse uptake of entire thyroid gland
Grave Disease tx?
1st medical management
PTU, Methimazole, beta blocker
2nd
Radioactive ablation
3rd - Surgical tx
Thyroidectomy
If grave’s needs thyroidectomy what is important to do pre-op?
Must be euthyroid
Beta blocked + Lugol’s solution 14 days prior to surgery
To avoid thyroid storm
Toxic multinodular goiter - pathophys
Prolonged low grade TSH stimulation - cause
Toxic multinodular goiter Tx
Total or subtotal lobectomy
because iodine ablation doesn’t work as well
Hyper-Thyroid workup
1st: TSH
If low then think hyperthyroid
2: US w/ FNA
Hashimoto’s thyroiditis pathophy, s/s, treatment?
Chronic lymphocytic thyroiditis
Anti thyroid antibodies
Enlarged painless thyroid
Tx: Tyroid replacement
Dequervian’s (subacute granulomatosis thyroiditis) pathophy, s/s, treatment?
Viral etiology Painful Elevated ESR Dec radioiodine uptake Tx: Pain control, beta blockers, steroids
Palpable thyroid nodule workup
5% turn out to be malignant
H/P: Hx of radiation, FHx of thyroid and endocrine cancers
Labs: TSH
Imaging: US - hypoechogenicity, microcalcification, irregular margins, lymphatic invasion
Thyroid scintigraphy: Distinguish btw solitary toxic adenoma and graves disease with cold nodules
FNA Biopsy: Solid hypoechoic nodule > 10 mm
Bethesda Criteria
6 possibilites, if discordinant with imaging repeat biopsy.
Repeat FNA if non diagnostic, Follicular cells of undetermined significance;
Just due lobectomy if follicular neoplasms;
If suspicious for malignancy do lobectomy w/ frozen section to see if you need to do a total
1: Non diagnostic - repeat FNA
2: Benign - Okay
3: Follicular of undetermined sig - repeat FNA
4: Follicular neoplasm - lobectomy
5: Suspicious of malignancy - lobectomy with frozen
6: Malignant - Total thyroidectomy
Papillary CA - MC cancer
Hx: irradiation to neck
Epidemiology: Women
s/s: Palpable lymph nodes, rare mets
Local invasion affects prognosis
Path: Orphan annie nuclei -> White circle, cleared out nuclei
Tx: Total thyroidectomy - b/c 3 benefits - Removal of potential multifocal disease, preparation of post op radioiodine therapy, able to use thyroglobulin for surveillance
What if with papillary CA identify + nodes, biopsy of nodes shows thyroid tissue, or intraop have + nodes
Tx: Total thyroidectomy, expand dissection (include level 6), removal of nodes in section where nodes are posititve
Adjuvant therapy?
Adjuvant radioactive iodine when TSH elevated ->4-6 weeks post op
Hold exogenous thyroid hormone (levothyroxine - because long half life), or give a recombinant TSH b/c shorter half life post op
Follicular thyroid CA
Hematogenous spread
Rare lymph spread
Hurthle cells - more aggressive follicular
Tx: Total thyroidectomy after lobectomy for diagnosis, w/ radioactive iodine ablation
Modified radical neck dissection (if positive nodes)
Medullary thyroid CA
Parafollicular C cells - neural crest origin, 4th pharyngeal pouch
Produces calcitonin - if > 400 then higher likelihood of mets
Radioactive iodine is ineffective
50% secretes CEA
20% germline mutations in RET proto-oncogene (MEN, familial thyroid cancer)
80% sporadic
Tx: Total thyroidectomy w/ central node dissection if - nodes
Total thyroidectomy w/ central and lateral node dissection if + nodes (levels 2-6)
Surveillance: Measure calcitonin and CEA levels q 6 months for 1 year, then annually afterwards
Central node dissection
level 6
Lateral node dissection
Levels 2-5
Anatomic variation - non recurrent R laryngeal nerve
Arteria lucoria: Aberrant R subclavian artery
How to avoid injury to superior laryngeal nerve
Ligate superior pole vessels close to thyroid
Monitor for surveillance
Total thyroglobulin
Most active thyroid hormone
T3
Where is T3 most produced?
Peripherally with deiodinase
Midline mass moves up and down with patient swallowing?
Thyroglossal duct cyst- Remanant of foramen cecum
Tx: Resect cyst with mid point of hyoid bone, b/c of small risk of malignant regeneration and risk of infection
What causes fever, tachycardia, HTN post op in pt with Graves?
Thyroid storm
Did not pre-op with beta blockade, PTU, lugols
Tx: Cooling blankets, beta blockade, PTU, lugols, O2
Elevated calcitonin most common symptom?
Diarrhea
MEN 2A when is prophylactic thyroidectomy
6 y.o
MEN 2B when is prophylactic thyroidectomy
< 2 y.o.
Likelihood of thyroid cancer in a kid < 14 w/ thyroid nodule
50%
Most commonly papillary cancer
Acute suppurative thyroiditis most common organisms
Staph aureus
Strep pyogenes
Acute suppurative thyroiditis presentation
Tender, fluctuant goiter, Inc WBC, normal thyroid function tests, age 20-40 y.o.
Acute suppurative thyroiditis diagnosis
Imaging - US
FNA -> Gram stain and culture
Acute suppurative thyroiditis treatment
IV abx
If pyriform sinus fistula or abscess then surgical drainage
Non tender asymptomatic thyroid nodule w/o adenopathy workup
US
FNA
(scintigraphy not useful, it is useful if the person is hyperthyroid and you want to know if hot or cold nodule)
Malignant US findings
Heterogeneous Hypoechoic Microcalcifications Hypervascular Cervical Adenopathy
Treatment for nodule in Men > 60
Excision
Risk of cancer goes from 12 -> 70% from age 60->70 in men.
Men at higher risk for nodule being cancer, women at higher risk for having a nodule
Cold nodule more likely to be cancerous.
Myxedema coma presentation
hypothyroidism; hypocortisolemia; hypoventilation, often requiring intubation; hypothermia; hyponatremia; hypotension; hypoglycemia; and infection. Insulin administration would be inappropriate in the setting of hypoglycemia.
