Thyroid

Question 1

TPO antibodies correlate with Hashimoto’s hypothyroidism but are NOT necessary for diagnosis. When would we ever use them?

Answer 1

In a patient with “subclinical hypothyroidism” (elevated TSH, normal T4). If they were anti-TPO+, we would know they have an additional 4% risk of getting hypothyroidism each year

Question 2

Name 3 situations in which a serum thyroglobulin level (thyroglobulin = glycoprotein involved in storage of thyroid hormone) would be useful

Answer 2

1. High thyroglobulin suggests hyperthyroidism or destructive thyroiditis
2. Intake of exogenous thyroid hormone suppresses thyroglobulin
3. Papillary and follicular thyroid cancer marker (should be zero after thyroidectomy/radioactive iodine ablation)

Question 3

Patient has thyroid nodule. CBC, TSH, BMP normal. Ultrasound shows 2 cm solid nodule. What is the next best step?

Answer 3

FNA (because its >1cm). No point doing a thyroid scan and radioactive iodine uptake test because TSH is not suppressed, so we already know its not producing.

Question 4

When is FNA indicated?

Answer 4

Nodule bigger than 1cm OR

Question 5

What is the cancer risk for any given thyroid nodule?

Answer 5

5-10%

Question 6

What factors make a thyroid nodule more likely to be canceR?

Answer 6

• Young (60) age
• Male
• History of head or neck radiation
• FH of thyroid cancer (esp. medullary)
• Nodule >1 cm
• Rapid nodule growth
• Hoarseness
• Cold nodule (not suppressing TSH)

Question 7

For how many weeks of birth does the baby rely on the mother’s thyroid hormone?

Answer 7

10-12 weeks

Question 8

What is goal T4 and TSH for a pregnant woman?

Answer 8

Goal T4: 1.5x normal
Goal TSH: Lower end of normal

…may have to increase levothyroxine dose by 35-50% in order to do this!

Question 9

What happens to TBG and T4 in pregnancy?

Answer 9

TBG levels go up, which binds up more T4, so T4 levels decrease

Question 10

What is normal range TSH? T4?

Answer 10

TSH: 0.4-4.2 microunits/mL
Free T4: 0.7-1.9 mg/dL???
T3: 75-200 ng/dL???