Endocrine: Thyroid Flashcards
The thyroid descends from the ______ during fetal development
Foramen cecum (at the base of the tongue)
Zuckerkandl tubercle (a posterior nodular extension of the thyroid that can help with locating the recurrent laryngeal nerve that exists medial to this tubercle)
How can you find the recurrent laryngeal nerve on imaging?
It should be medial to the Zuckerkandl tubercle (a posterior nodular extension of the thyroid)
Which thyroid cancer is classically associated with microcalcifications…
Papillary thyroid cancer
Thyroid ultrasound
Colloid nodule
Note: Comet tail artifact.
Which features would make a thyroid colloid nodule more suspicious?
- Microcalcifications
- Increased vascularity
- Solid components
- Large size (> 1.5 cm)
- Being cold on I-123 nuclear imaging
Solitary thyroid nodule with microcalcifications…
Think papillary thyroid cancer
Note: Microcalcifications in a multinodular goiter are less suspicious.
What is the most specific imaging feature (and highest positive predictive value) for thyroid malignancy?
Microcalcifications
Thyroid nodule with a complete hypoechoic halo…
Highly suggestive of benign nodule
Thyroid nodule with peripheral vascularity…
Likely benign
Thyroid nodule with central vascularity…
Suspicious for malignancy
Note: Solid, hypervascular nodules are more likely to be malignant.
What ultrasound feature has the highest sensitivity for thyroid nodule malignancy?
Solid composition
Note: Pure cystic or spongiform (>50% cystic) echo texture are likely benign.
Ultrasound follow up shows a solid thyroid nodule becoming more cystic over time…
Likely benign
Are hyperechoic or hypoechoic thyroid nodules more concerning?
The more hypoechoic, the more concerning for malignancy
Is size or suspicious features more important when deciding whether to biopsy a thyroid nodule?
Suspicious features
Note: Size is not predictive of malignancy in thyroid nodules.
Are solitary thyroid nodules or multinodular thyroids more concerning?
The risk of cancer per nodule is lower in a multinodular thyroid; however, because there are more nodules the summed risk of thyroid cancer is usually higher in multinodular thyroids.
Thyroid ultrasound
Think hyperfunctioning (toxic) adenoma
Note: Mostly solid thyroid nodule that is hot on I-123 scan (nodule uptake with relatively suppressed background thyroid uptake).
Goiter
A thyroid that is too big
Differential for a goiter
- Multinodular thyroid
- Graves disease
- Low iodine (especially if pt is malnourished)
Female with painful thyroid after an upper respiratory infection…
Think subacute thyroiditis (De Quervains thyroiditis)
Hyperthyroidism followed by hypothyroidism in a pregnant pt with a painless thyroid…
Think Subacute thyroiditis (De Quervains thyroiditis)
Note: In pregnant women, subacute thyroiditis is often painless. Initial hyperthyroidism is due to spilling of thyroid hormones, which if followed by hypothyroidism.
De Quervain thyroiditis
AKA subacute thyroiditis is thyroid inflammation (usually painful, though not during pregnancy) that occurs after an upper respiratory infection
Note: Usually pt will be hyperthyroid during the acute phase and then become hypothyroid.
Iodine radiotracer uptake during the acute phase of subacute/De Quervain thyroiditis…
Decreased
Note: Even though pts are hyperthyroid during the acute phase, this is due to spill of thyroid hormones (not overproduction). Thyroid hormone production is actually turned off because the pt is hyperthyroid, which is why uptake is decreased.
Acute suppurative thyroiditis
A bacterial infection of the thyroid gland, which may progress to a thyroid abscess
Pediatric pt with recurrent acute suppurative thyroiditis
Think 4th branchial cleft cyst
Note: Infection starts in 4th branchial cleft cyst and travels via a pyriform fistula to the thyroid.