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Prognostically poor characteristics in thyroid cancer.
- Age, males >41, females >51
- Extent (extrathyroidal extension)
- Size greater than 5 cm
- Also: h/o radiation, thyroiditis, and children with mets
RET and BRAF abnormalities are associated with which thyroid neoplasm?
- RET and BRAF: PTC
- RAS: follicular ca
- RET: MTC
Thyroid lobes arise from which branchial derivative?
- Fourth branchial arch
- (superior para and parafollicular c cells from fourth pouch, inferior para from third pouch)
The inferior thyroid artery is commonly found in which orientation in relation to the RLN?
These structures cross one anther. The inferior thyroid artery is anterior to the RLN 70% of the time.
The external branch of the SLN is ___ to the superior thyroid artery
The right recurrent nerve loops around this structure/embryologic derivative. The left?
- Right: subclavian (fourth arch)
- Left: ligamentum arteriosum (sixth arch)
A nonrecurrent RLN occurs on the ___ side and is associated with what other anomaly.
- Right (unless pt has situs inversus, then left)
- Retroesophageal subclavian artery
___% of patients have 4 parathyroid glands
___% of patients have more than 4
- 80% have 4
- 10% have more than 4
Syndromes associated with well-differentiated thyroid carcinoma
- the MEN syndromes
- Gardner's (polyposis coli)
- Cowden's (multiple hamartomas almost everywhere)
What is Pemburton's maneuver, and what does it evaluate?
For thoracic inlet obstruction in substernal goiters. Pt raises his or her arms over the head, positive findings include subjective respiratory discomfort or venous engorgement of face.
What defines a T3 thyroid carcinoma?
- >4 cm or with extension into the perithyroid soft tissue, including muscle.
- extension into subcutaneous tissue, larynx, trachea, esophagus, or RLN makes it T4
Describe the nodal staging for thyroid carcinoma
- N1a: pretracheal, paratracheal, delphian mets
- N2b: any other mets
A generous prognosis is given to those patients with papillary or follicular thyroid CA younger than the age of __ years? What is the staging system.
- For patients 45 years and younger:
- Stage 1: M0
- Stage 2: M1
False positive rate of FNA in diagnosing PTC
Next step after obtaining a nondiagnostic FNA of a thyroid nodule
- 15% of FNAs are nondiagnostic
- repeat FNA
- if repeat FNA is nondiagnostic consider hemithyroidectomy
- In this scenario, 4% of women and 29% of men, hemi shows carcinoma
Where is a Delphian node found?
What three proteins bind thyroxine (T4)?
Thyroxine-binding globulin (75%), thyroxine-binding prealbumin (15%), albumin (5%)
Between T3 and T4, which is more plentiful and which is more potent?
- T4 is 90% of thyroid output
- T3 is 4 times more active, binds with higher affinity to TBG
Common goal range of TSH in a low-risk pt now free of disease when titrating synthroid?
- TSH 0.3-2 mIU/mL (low-normal)
- High risk, free of disease: 0.1-0.5
- Persistent disease: <0.1
- Based on ATA guidelines
What do the thinamides (PTU, methimazole) do? What are some adverse effects of these drugs?
- Inhibits T4 conversion and organification of iodine
- May cause hepatitis, agranulocytosis, parotitis
Factors that favor malignancy in pt with thyroid nodule.
- age <20 or greater than 70 years old
- Neural involvement
- Family hx
- Cervical LAD
- Radiation exposure
Thyroid FNA reveals deposits that stain with congo red. Dx?
Medullary ca (amyloid deposits)
99mTc pertechnetate is trapped by which cells? What are the advantages of this test over radioactive iodine?
- Trapped by follicular cells, does not measure uptake
- Adv: low dose radiation, less expensive, images obtained in 30 min
In what two scenarios would you use I-131?
- This test has a high radiation dose and requires 2-3 days for results
- Tracer of choice for evaluation of mets
- Used for ablation in hyperthyroidism or residual disease
Malignancy rate in cold nodules? Hot?
Malignancy rate in hot nodules is 4%
Most common benign adenoma of the thyroid?
Follicular. Papillary adenoma is exceedingly rare
Most common thyroid cancer?
In PTC, risk of metastasis?
- Palpable neck 15-30 %
- Occult neck 70%.
- Distant 5-10%
What nuclear medicine procedures will typically follow thyroidectomy for PTC?
6 weeks- RAI uptake study followed by I-131 ablation
How do you monitory a patient s/p thyroidectomy for PTC?
Whole body RAI uptake 6-12 months then 2 years. serum thyroglubulin
What is the 5 year survival for each of the well-differentiated thyroid carcinomas?
- Papillary: 95%
- Follicular 70-85%
- Hurthle cell: 50%
- Medullary 50-80%
Poor prognostic factors for PTC
- Tumor >1.5 cm
- Extra capsular spread
- Cervical mets doesn't affect survival, only increases risk of nodal recurrence
Poor prognostic factors for medullary
- Sporadic (not familial)
- Younger pt
Management of medullary thyroid ca
- Total thyroid, elective MRND
- Medical thyroid suppression
- Annual screening with pentagastrin stimulated calcitonin levels
- (Parafollicular cells do not take up iodine, so RAI is not effective)
What percentage of MTC is sporadic?
What percentage of MTC has lymph node involvement?
- Only 8% distant mets
What serum tests can suggest MTC?
- Ret-3 oncogene on chromosome 10
- Elevated calcitonin (can stimulate with pentagastrin)
- Elevated CEA
Lymphoma of the thyroid is most commonly of which type?
Primary lymphoma of the thyroid can be associated with which underlying thyroid pathology?
- Chronic lymphocytic thyroiditis
Treatment of primary lymphoma of the thyroid?
Usually RT, but surgery can be used of disease is confined to the thyroid
What effect does KI (lugol's solution) have in the preoperative management of thyroid disease?
Reduce vascularity of the gland, reducing risk of thyroid storm.
Risk of death in thyroid storm?
Management of thyroid storm
- PTU (give at least 30 minutes before iodine)
- Inorganic iodine
- Supportive measures
How does iodine deficiency produce goiter?
Elevates TSH, chronic thyroid hyperplasia.
Tests to establish Graves diagnosis
- Thyroid-stimulating immunoglobulin levels
- Diffuse uptake of RAI
Most common cause of hypothyroidism in US
Patient presents with rock hard thyroid gland and hypoyroidism. Likely diagnosis?
Reidel's thyroiditis. Thyroid fibrosis of unknown etiology. Consider isthmus release for symptoms of pressure.
Most common location of the superior parathyroid
Posterolateral aspect of the superior pole, 1 cm above intersection of inf thyroid artery and RLN.
Most common location of inferior parathyroid
- More variable location than superior
- 1-2 cm inferior to junction of inf thyroid artery and thyroid gland
What percentage of serum calcium is bound to albumin?
What happens to Albumin/calcium complex in acidosis?
H+ competes with Ca, so acidosis increases serum Ca.
Average weight of a parathyroid
Effect of PTH on serum phosphate?
Decreases PO4 by increasing PO4 excretion in kidneys
What percentage of primary hyperparathyroidism is caused by a single adenoma?
What is tertiary hyperparathyroidism?
Parathyroid hyperplasia from secondary hyperparathyroidism becomes autonomous and irrepressible.