Thyroid lecture, extra Qs

Question 1

Pt with hypothyroidism: What drugs are on your differential? (4)

Answer 1

Primary: antithyroid agents, lithium

Scondary: DA, glucocorticoids

Question 2

How can TSH be within the reference range in secondary/tertiary hypothyroidism?

Answer 2

Think: Pituitary tumor that inhibitis TSH secretion.

-Initially, low TSH from pituitary reduces TH release. High TRH stimulates remaining functioning pituitary to try to raise its TSH secretion, but it is unable to.

“Inappropriately un-elevated”

Question 3

You start Hashimoto’s with levothyroxine. What do you check to monitor adequate replacement, and when do you next check?

Answer 3

Check TSH in 6 weeks.

-TSH has long half life, you want to reach steady state

Question 4

Methimazole vs PTU

• when to use PTU over methimazole (2)
• most feared side effect of each. (so what to monitor?)

Answer 4

1. 1st trimester pregnancy. fewer birth defects
2. Thyroid storm–high dose can reduce T4 to T3 conversion immediately, which can help in thyroid storm. Peroxidase blocking activity is irrelevant b/c it takes much longer time to reduce TH
   - reversible agranulocytosis! So monitor WBC count

Question 5

Nuclear fallout: How to protect your thyroid?

Answer 5

Take iodine. This keeps your thyroid from uptaking radioactive iodine in the radioactive fallout.

Question 6

Your patient is euthyroid (normal free TH), but total TH may be abnormal

When does this happen? (3)

Answer 6

High estrogen increases TBG

1. pregnancy
2. oral contraceptives

Low TBG production from liver

3. Liver problems, ICU

Question 7

new onset hypothyroidism after what age does not affect brain maturation?

Answer 7

Hypothyroidism after age 3