Lec 05: Diagnostic Tests in Thyroid Disorders Flashcards

1
Q

T/F: Approximately 1 out of 10 Filipinos has abnormalities in their thyroid function tests (TFTs).

A

T

8.53%

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2
Q

T/F: Majority of the Filipinos with TFT abnormalities have subclinical thyroid disease.

A

T

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3
Q

Reasons for doing thyroid function tests EXCEPT

A. formulate a primary working impression
B. supplement physical exam findings
C. monitor clinical response to treatment
D. determine risk for malignancy
E. NOTA

A

A.

Formulation of primary working impression should be based primarily on history and PE.

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4
Q

ID: What is the only available function test in the 1950s?

A

indirect estimation of thyroxine (T4)

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5
Q

ID: What hormone establishes the set point in the regulation of the H-P-T axis?

A

TSH

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6
Q

ID: Probable diagnosis

↓ TSH, ↑ T4, ↑ RAIU

A

Graves’ disease
hyperfunctional multinodular goiter
hyperfunctional thyroid adenoma

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7
Q

True of iodide uptake

A. mediated by sodium-iodide symporter (NIS)
B. occurs at the basolateral membrane
C. extracts normally around 10-25% of serum iodide
D. A & B only
E. AOTA

A

E. AOTA

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8
Q

ID: What transports iodide from the thyrocyte to the follicular lumen?

A

pendrin

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9
Q

ID: This protein receptor mediates endoyctosis of thyroglobulin back into the thyrocyte.

A

megalin

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10
Q

True of TSH EXCEPT

A. first line test in most clinical setting
B. may be sufficient to diagnose a patient
C. exhibits log-linear relationship with T4
D. controls the H-P-T axis
E. NOTA

A

B.

TSH is not enough to diagnose a patient. FT4 / FT3 must also be tested.

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11
Q

T/F: A linear fall in FT4 produces a linear increase in TSH.

A

F

It results in LOGARITHMIC increase in TSH. (log-linear relationship)

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12
Q

ID: When does TSH peak in a normal ambulatory patient?

A

between midnight to 4:00 am

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13
Q

True of TSH testing

A. single determination is usually adequate
B. half-life is around 20 minutes
C. good specificity for detecting TSH secreting tumor
D. A & B only
E. AOTA

A

A.

Modest excursions, low variations in levels, and long half-life (50 mins) renders a single TSH test adequate.

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14
Q

What is the concern in TSH testing in hospitalized patients?

A

Non-thyroid illnesses / co-morbidities may alter lab results.

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15
Q

The following drugs increase TBG levels EXCEPT

A. estrogens
B. 5-fluorouracil
C. nicotinic acid
D. glucocorticoids
E. NOTA
A

D.

The following drugs decrease TBG

  • thyroid hormones
  • androgens
  • anabolic steroids
  • glucocorticoids
  • L-asparaginase
  • interleukin-6
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16
Q

The following illnesses / conditions decrease TBG levels EXCEPT

A. nephrotic syndrome
B. hepatic failure
C. chronic alcoholism
D. AIDS
E. NOTA
A

D.

The following conditions increase TBG

  • pregnancy
  • hypothyroidism
  • hepatitis
  • hepatocellular carcinoma
  • adrenal insufficiency
  • AIDS
  • angioneurotic edema
17
Q

ID: This is a specific test for Graves’ disease.

A

thyroid stimulating immunoglobulin (TSI)
- TSI is a type of TSH receptor autoantibody (TRAb)

TSI is almost never found in other autoimmune thyroid disease.

18
Q

ID: Probable diagnosis

↓ TSH, ↑ T4, ↑ RAIU, (-) TSI

A

toxic thyroid nodule

19
Q

True of thyroglobulin EXCEPT

A. only found in thyroid tissue
B. most useful as a tumor marker for recurrence
C. utilized for anaplastic thyroid cancer screening
D. measure simultaneously with anti-Tg
E. NOTA

A

C.

Anaplastic and undifferentiated thyroid cancers do not produce thyroglobulin, hence testing using Tg is not useful.

20
Q

True of thyroid peroxidase autoantibodies (TPOAb)

A. positive in Graves' disease
B. positive in Hashimoto thyroiditis
C. positive in aging individuals
D. A & B only
E. AOTA
A

E. AOTA

Sensitivity is higher though with Hashimoto thyroiditis.

21
Q

True of urine iodine content testing EXCEPT

A. utilized in iodine deficiency diagnosis in individuals
B. ingested iodine is bound to serum proteins
C. main serum protein is albumin
D. unbound iodine is excreted in urine
E. NOTA

A

A.

It is commonly utilized to diagnose iodine deficiency in POPULATIONS not in individuals.

22
Q

ID: A population is said to be iodine deficient when the median urinary iodine concentration reaches what level.

A

< 50 ug/L

23
Q

T/F: Thyroid ultrasound uses low frequency waves to for clearer imaging.

A

F

It uses high frequency waves (7.5-14.0 megahertz).

24
Q

ID: This can be used alongside UTZ to determine blood flow.

A

Doppler

25
Q

ID: This method detects around 50% prevalence of thyroid nodules.

A

autopsy

palpation - 4%
UTZ - 30%

26
Q

What is the usual management for unsatisfactory fine needle aspiration biopsy (FNAB) specimen?

A. repeat FNA with ultrasound guidance
B. proceed to surgical lobectomy and biopsy
C. do clinical follow up
D. start therapy
E. NOTA
A

A.

27
Q

Enumerate the four molecules used in radioisotope scans.

A

I-123
I-125
I-131
Tc-99m

28
Q

In whole body scan, where do metastatic thyroid tissue tend to localize?

A

skull and long bones

29
Q

ID: Probable diagnosis

↓ TSH, ↓ T4, ↓ RAIU, (-) TSI

A

pituitary abnormality

30
Q

Which iodine isotope produces the best image quality?

A

I-123

It also has a short half-life (0.55 d).