Pharm: Thyroid

Question 1

What is the organification step the biosynthesis of TH?

Answer 1

Adding of Iodine to the tyrosine residues on thyroglobulin

Question 2

Name the two drugs used in management of hypothyroidism.

Answer 2

Levothyroxine (Isomer of T4)

Liothyronine (isomer of T3)

Question 3

Which drug is used for myxedema coma?

Answer 3

IV levothyroxine
-this condition is an emergent exacerbation of hypothyroidism and sometimes the faster-acting T3 isomer is needed to reverse the condition so
Liothyronine can also be used but is more difficult to monitor

Question 4

What are symptoms of myxedema coma?

Answer 4

altered mental status, hypothermia, hypoglycemia, hypotension, hyponatremia, hypercapnia, hypoxia, bradycardia, and hypoventilation

ironically myxedema is not always present

Question 5

How is myxedema treated?

Answer 5

Begin with low doses

Myxedema is a manifestation of severe hypothyroidism. The treatment is replacement of TH (either Liothyronine or Levothyroxine). However, myxedema is associated with coronary artery disease. Giving TH too quickly will increase metabolism in the body and O2 demand on the heart and exacerbate angina pectoris, cause MI or arrhythmias.

Question 6

Name the two drugs that induce CYP causing hypothyroidism.

Answer 6

Rifampin, Phenytoin

-induce metabolism of T3 and T4

Question 7

Antiarrhythmic that causes hypothyroidism and the mechanism.

Answer 7

Amiodarone

• resembles TH and releases lots of iodine into the blood.
• a high amount of iodine is taken up by the thyroid gland inducing an autoregulation mechanism (Wolff-Chaikoff effect)
• the WC effect prevents organification and release of TH

Question 8

Name the serious cardio, MSK, and neuro side effects of Levothyroxine and Liothyronine.

Answer 8

Cardio: MI
MSK: decreased bone density, hip fracture
Neuro: pseudotumor cerebri, seizure

Question 9

Name the two drugs used for Hyperthyroidism therapy and the MOA.

Answer 9

Methimazole
Propylthiouracil

MOA: inhibit thyroid peroxidase (TPO)

(Propylthiouracil also inhibits deiodination of T4 to T3)

Question 10

First line drug for children and adults with hyperthyroidism.

Answer 10

Methimazole

Question 11

Contraindication of methimazole.

Answer 11

Teratogenic (-azole ending)

• causes fetal scalp defect
• ability to cross placenta because it does not bind plasma proteins

Question 12

Which 3 clinical settings prefer propylthiouracil to methimazole in treatment of hyperthyroidism?

Answer 12

1. Pregnncy
2. Life-threatening thyrotoxicosis or thyroid storm
3. Patients with adverse rxns to methimazole

Question 13

Major side effects of the thioamides.

Answer 13

Methimazole: rash, altered sense of smell, agranulocytosis

Propylthiouracil: rash, liver toxicity

Question 14

In what setting is antithyroid medication preferred for treatment of hyperthyroidism?

Answer 14

Best for children and adults with mild disease

Question 15

In what setting is surgery the best treatment for hyperthyroidism?

Answer 15

Best for large glands or multinodular goiters

Question 16

In what setting is radioiodine ablation of the thyroid best.

Answer 16

In patients older than 21

Question 17

What are the 3 steps in surgical removal of the thyroid gland?

Answer 17

1. Treat w/ anti-thyroid meds to until euthyroid state (normal TH hormone levels) is reached
2. Administer Potassium Iodide to induce the WC effect and reduce vascularity to the organ
3. Perform the surgery

Question 18

Contraindication to thyroid gland surgery.

Answer 18

Pregnancy

• potassium iodide causes fetal goiter
• other drug options are available but are not very effective

Question 19

MOA of radioactive iodine

Answer 19

MOA: iodine rapidly absorbed by thyroid cells, emits beta-rays that destroy thyroid parenchyma

Question 20

Name the two Beta blockers used in hyperthyroidism and why.

Answer 20

Propranolol (preferred)
Esmolol

-both are used to treat symptoms: sweating, tachycardia, tremor