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Nucs Board Review > Oral Exam - Thyroid and Parathyroid > Flashcards

Oral Exam - Thyroid and Parathyroid Flashcards

1
Q

Grave’s findings

A

○ Homogeneously enlarged thyroid with markedly
increased radiotracer uptake

○ Decreased uptake in salivary glands

○ Superimposed nodules occur in 5-10%
– Consider Marine-Lenhart syndrome

• RAI: Usually > 50%, often 80-90%

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2
Q

Thyroid scan protocol

A

– Radiopharmaceutical:
I-123 (200-400μCi PO
Tc-99m pertechnetate (2-10 mCi)

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3
Q

Thyroid uptake dose

A

Radiopharmaceutical
□ I-131: 5-10μCi(0.2-0.4MBq) I-131 for uptake if planning Tc-99m pertechnetate scan

□ I-123: can do uptake and scan with same dose (200-400 uCi)

○ Uptake acquisition
– 24 hr most common, may add 4hr uptake to evaluate for rapid turnover

○ NormalRAIUvalues(varybyinstitution)
– 4hr:~5-15%
– 24hr:~10-35%

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4
Q

Differential Graves

A

Subacute thyroiditis - low RAIU (<5%)

MNG - heterogeneous, RAIU not as high

Toxic adenoma - nodule, RAIU not as high

Autoimmune thyroiditis - Hashimoto’s with hashitoxicosis (anti-TPO, anti-thyroglobulin); Silent/post-partum

Medication/contrast -

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5
Q

Graves treatment

A

PTU/Tapazol - Rare agranulocytosis and hepatic dysfunction

RAI
Empiric - SEE NEW NOTES
Calculated - SEE NEW NOTES

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6
Q

MNG findings

A

○ Heterogeneous uptake in enlarged thyroid gland with multiple variable-intensity nodules

○ Dominant cold nodule in MNG: 5% chance of malignancy

○ May extend substernally

○ Evaluate for dominant cold nodule (large, cold nodule
when compared with other nodules)

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7
Q

RAIU in nodular thyroid disease

A

– Can be low, normal, or mildly elevated (often<50%)
in thyroid nodular disease

– Obtained in patients with hyperthyroidism
– Used for diagnosis and radioactive iodine therapy
planning

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8
Q

DDx cold or warm nodule

A

Cyst/hemorrhage/abscess
Adenoma - non-functioning
Carcinoma - thyroid, lymphoma, metastases
Parathyroid adenoma

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9
Q

Ddx hot nodule

A

Functioning adenoma
Focal thyroiditis
Discordant nodule on Tc99m pertechnetate (traps, does not organify)
Toxic multinodular goiter

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10
Q

Dual phase Sestamibi protocol

A

– 20-30 mCi Tc-99m sestamibi/tetrofosmin

○ Early images
– 10-20 min post injection
– Activity in thyroid and parathyroid adenoma

○ Delayed images
– 90 min post injection
– Activity in thyroid washes out, activity in adenoma
persists
□ ~60% of adenomas retain radiotracer longer than
thyroid

○ SPECT/CT
– SPECT/CT at 90 min (after thyroid washes out)
– Better to localize activity posterior to thyroid, in
tracheoesophageal groove, or to ectopic site

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11
Q

• Dual radiotracer protocol

A

Sestamibi + 10-20 mCi Tc-99m pertechnetate

○ Tc-99m sestamibi parathyroid scintigraphy to localize thyroid and parathyroid adenoma
○ Thyroid-only radiotracer to distinguish borders of thyroid gland:Tc-99m pertechnetate or I-123
○ Often used when Tc-99m sestamibi parathyroid scintigraphy indeterminate

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12
Q

Ddx parathyroid adenoma

A

Parathyroid hyperplasia
Parathyroid carcinoma
Other malignancy
Thyroid adenoma

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13
Q

Location of Parathyroid glands

A

○ Posterioror inferior to thyroid (mostcommon)
○ Intrathyroidal(2%): Withinthyroidparenchyma
• Ectopic (5-10%)

• Supranumerary
○ 25% may have 5 or more glands

• Multiple adenomas
○ 4-5% have multiple adenomas
○ Consider parathyroid hyperplasia

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14
Q

RAI treatment dose Graves

A

10-15 mCi

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15
Q

RAI treatment dose MNG

A

10-20 mCi

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16
Q

Post-op - pre-therapy thyroid scan

A

Used if post-op stage not adequately assessed

I123 preferred

Should be done within 72 hours of therapy

17
Q

Thyroid CA risk stratification

A

Low risk:

  • No local/distant mets
  • No tumour invasion
  • Non-agressive histology (not tall cell)
  • Clinical N0 or <= 5 micromets on path
18
Q

Low risk RAI

A

If total thyroidectomy - RAI not routinely recommened
- if so, 30 mCi

If subtotal thyroidectomy - RAI not recommended

19
Q

Moderate risk

A

Consider RAI

20
Q

High risk

A

Routinely recommend RAI

21
Q

Benefits RAI

A

Reduces risk of local recurrence
Prolongs survival in patients with lung and/or bone metastases
Eliminates sources of Tg to facilitate follow-up
Helps complete staging

22
Q

RAI dosing recommendations

A

For RAI remnant ablation
Dose of 30 mCi recommended

For treatment of suspected microscopic residual disease
Dose up to 150 mCi can be considered

Lung mets
100-200 mCi (Max 150 if > 70)

Bone mets
100-200 mCi

23
Q

Mediastinal uptake on Thyroid scan

A

Substernal uptake in an enlarged gland

Physiologic thymic uptake

24
Q

Grave’s bloodwork

A

Anti-TSH antibodies
Anti-thyrotropin receptor antibodies

If inferior activity, ask to swallow water

25
Q

Sestamibi

A

Non-specific malignancy/inflammatory agent

26
Q

Rising thyroglobin with negative I131 post-op scan

A

Do F18-FDG PET for de-differentiated thyroid CA

27
Q

Follow-up for hot nodule on Tc99m-pertechnetate study

A

Consider I123 scan to exclude a discordant nodule

28
Q

Subacute thyroiditis differential on thyroid scan (low uptake, clinically thyrotoxic)

A 
Subacute thyroiditis (granulomatous, post-partum, silent)
Exogeneous thyroid use
Amiodarone
Iodine load
Struma ovarii
29
Q

Ddx lingual thyroid

A

Hyperfunctioning thyroid adenoma

Ectopic thyroid

30
Q

Hashimoto’s

A

Early hashimoto’s can be associated with an increased RAIU, mimicking Grave’s

Thyroid hormon production is inefficient and TSH should be increased (hypothyroid)

Same pattern in early phase of subacute thyroiditis

31
Q

Ddx Poorly visualized thyroid gland and clinical hypothyroid

A

After I131 ablation, surgery, radiation
Hashimoto’s
Amyloid

32
Q

Ddx Poorly visualized thyroid gland and clinical euthyroid

A

Iodine load
IV contrast
Amiodorone
Antithyroid medications

33
Q

Ddx Poorly visualized thyroid gland and clinical hyperthyroid

A

Subacute, silent, or post-partum thyroiditis
Facticious
Amiodorone
Ectopic thyroid tissue - mets or struma ovarii

Nucs Board Review (21 decks)

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