Thyroid Drugs (Staudinger)

Question 1

What are the 4 thyroid hormone agonists?

Answer 1

1. Levothyroxine (T4)
2. Liothyronine (T3)
3. Liotrix
4. Thyroid desiccated

Question 2

What are the 4 anti-thyroid agents?

Answer 2

1. Radioactive iodine
2. Potassium iodide
3. Methimazole (10X more potent then PTU)
4. Propylthiouracil (PTU)

Question 3

Propranolol

Answer 3

non selective beta blocker; indicated in thyrotoxicosis (thyroid storm); reduced heart rate and tremors; inhibits peripheral conversion of T4 to T3 by blocking monodeiodinase I & II and blocks the B1 receptor on the heart

Question 4

What is the most sensitive screening test for both primary hyper and hypothyroidism?

Answer 4

TSH

Question 5

Thiocynate (SCN-) and Perchlorate (CIO4-)

Answer 5

environmental contaminants that inhibit the biosynthesis of thyroid hormones

Question 6

Amiodarone

Answer 6

an anti-arrhythmic drug that can cause thyrotoxicosis due to exceeding amount of iodine released (50X); pts on this drug will need baseline thyroid hormones measured before start and then every 6-12 months afterwards

Question 7

levothyroxine

Answer 7

T4 analogue; side effects of hyperthyroidism; has impaired absorption when taking with cholestramine

Question 8

Methimazole

Answer 8

anti-thyroid drug; blocks iodide organification by inhibiting thyroperoxidase (necessary enzyme in T3 & T4 synthesis

Question 9

Methimazole works by blocking which enzyme?

Answer 9

thyroperoxidase (necessary enzyme in T3 & T4 synthesis

Question 10

Propylthiouracil (PTU)

Answer 10

anti-thyroid drug; indicated in Graves disease and pts with a toxic multi nodular goiter; use if pts are intolerant of methimazole or if pregnant; does NOT inactivate pre-existing T4 and T3 but does stop the conversion of T4 to T3

Question 11

Potassium iodide

Answer 11

stable form of iodine; indicated in iodine deficiency; does NOT affect heart rate or produce irregular heartbeat

Question 12

Drug indicated in iodine deficiency?

Answer 12

Potassium iodine

Question 13

Radioactive Iodine (I-131)

Answer 13

indicated in thyroid cancer; gland absorbs the iodine and radiation destroys it; contraindicated in pregnant women

Question 14

When is radioactive iodine contraindicated?

Answer 14

in pregnancy

Question 15

Perchlorate blocking agent

Answer 15

competitive inhibitor of iodide uptake; indicated to control amiodarone induced thyrotoxicosis

Question 16

A 24 yr old women was found to have Graves disease. The decision has begun treat with methimazole. Methimazole reduces serum concentration of T3 primarily by which of the following mechanisms?

a. accelerating the peripheral metabolism of T3
b. Inhibiting the proteolysis of thyroid-binding globulin
c. Inhibiting the secretion of TSH
d. Inhibiting the uptake of iodide by cells in the thyroid
e. Preventing the addition of iodine to tyrosine residues on thyroglobulin

Answer 16

e. Preventing the addition of iodine to tyrosine residues on thyroglobulin; prevent conversion of tyrosine residues in thyroglobulin to MIT or DIT

Question 17

A 24 yr old women was found to have Graves disease. The decision has begun treat with methimazole. Though rare, a serious toxicity associated with the thioamides is which of the following?

a. Agranulocytosis
b. Lupus erythematous-like syndrome
c. Myopathy
d. Torsades de pointes
e. Thrombotic thrombocytes purpura (TTP)

Answer 17

a. Agranulocytosis (most dangerous)
Others: vasculitis, hepatic damage, and hypoprothrombinemia