Antithyroid Agents

Question 1

What is the basis for the selective cell destruction of the thyroid gland by 131I? Indications?

Answer 1

active accumulation of iodide into the gland/ hyperthyroidism

Question 2

Proteolytic release of T3 and T4 from thyroglobulin is inhibited by what therapy?

Answer 2

inhibited by high doses of iodide

Question 3

Conversion of T4 to T3 via 5’ deiodinase in peripheral tissue is inhibited by what drug therapy?

Answer 3

propranolol and PTU

Question 4

What are the thioamide drugs?

Answer 4

propylthiouracil (PTU), methimazole

Question 5

Indications for thioamides.

Answer 5

uncomplicated hyperthyroid conditions

Question 6

S/E of thioamide use?

Answer 6

maculopapular rash; agranulocytosis, liver failure (PTU)

Question 7

Why is PTU safer for use in pregnancy than methimazole?

Answer 7

While both drugs cross the placental barrier, PTU is safer in pregnancy because it is highly protein bound

Question 8

Indications for potassium iodide plus iodine (Lugol solution)?

Answer 8

thyrotoxicosis used preoperatively > dec. gland size, fragility, and vascularity

Question 9

Oxidation of iodide to iodine by peroxidase (TPO) is inhibited by what drugs?

Answer 9

thioamides

Question 10

Iodination of tyrosyl residues (organification) on thyroglobulin to form MIT and DIT is inhibited by what antithyroid drugs?

Answer 10

inhibited by thioamides

Question 11

Coupling of MIT and DIT to form T3 and T4 is inhibited by use of what drugs?

Answer 11

thioamides