Endo: Thyroid Pharm

Question 1

In Hashimoto’s Thyroiditis, what antibodies are present?

Answer 1

Anti-Thyroid Peroxidase or Anti-Thyroglobulin

Question 2

What is the first-line treatment for hypothyroidism?

How long does it take this drug to reach steady state levels?

Answer 2

Levothyroxine (synthetic T4)

Requires 6-8 wks to reach steady state levels

Question 3

How does dosing of Levothyroxine change during pregnancy?

Why? (2)

Answer 3

• During pregnancy, must increase dose of levothyroxine b/c
  
  • Increased TBG levels cause a decrease in free T3/4
  • Placental metabolism of free T4/3

Question 4

What is myxedema coma?

Tx?

Answer 4

Myxedema coma is end-stage hypothyroidism (decreased respirations, hypothermia, bradycardia, etc)

Treat with IV T4 and hydrocortisone

Question 5

When should levothyroxine be taken? (2)

Answer 5

Either 30 mins before breakfast or 3 hours after last meal of the day

(EMPTY STOMACH)

Question 6

Name 3 drugs that interfere with the absorption of levothyroxine

Answer 6

• Metal ions
• Ciprofloxacin
• Bile Acid Resins

Question 7

Assuming the Hypo-Pit-Thyr axis is intact, changes in Thyroid Binding Globulin will/will not affect free T4

Answer 7

Assuming the Hypo-Pit-Thyr axis is intact, changes in Thyroid Binding Globulin will not affect free T4

*Only total T4 will be affected

Question 8

Name one drug that increases TBG

Name 2 drugs that decreases TBG

Answer 8

• Estrogen increases TBG
• Phenytoin and Carbamazepine decrease TBG

Question 9

What enzyme converts T4 to T3?

Name 3 drugs that inhibit this enzyme

Answer 9

5’ deiodinase in periphery converts T4 into T3

This enzyme is inhibited by glucocorticoids, beta blockers, and amiodarone

Question 10

What is synthetic T3 called?

Why is it less preferable than T4? (2)

Answer 10

• Synthetic T3 = Liothyronine
• Worse than levothyroxine b/c
  
  • More cardiotoxic
  • Shorter half life, so greater fluctuations throughout the day

Question 11

ADR of levothyroxine

Answer 11

Symptoms of hyperthyroidism

(anxiety, heat intolerance, palpitations, weight loss)

Question 12

What are two ways to destroy the thyroid gland?

Answer 12

Take it out (surgery)

Radioactive iodine

Question 13

What are two drugs that lower the effects of thyroid hormone peripherally?

Answer 13

Beta blockers

Glucocorticoids

*These decrease the symptoms of hyperthyroidism

Question 14

MOA for Methimazole and PTU

Answer 14

• Both Methimazole and PTU inhibit thyroid hormone synthesis by inhibiting thyroid peroxidase
• PTU also blocks conversion of T4 into T3 in periphery

Question 15

Use of methimazole and PTU

Answer 15

Thyrotoxicosis due to hyperthyroidism only

*Do not use for thyroiditis

Question 16

What is the first-line treatment for hyperthyroidism in pregnant patients?

What is the first-line treatment for hyperthyroidism in non-pregnant patients

Answer 16

• Pregnant: PTU! (it crosses the placenta less easily than methimazole)
• Non pregnant: methimazole

Question 17

Name 2 side effects of both methimazole and PTU

Name 1 side effect only with PTU

Answer 17

• Both: rash, agranulocytosis
• PTU only: hepatotoxic

Question 18

Describe the MOA and use (2) of super saturated potassium iodide

Answer 18

• Inhibits synthesis and release of thyroid hormones by increasing plasma and intracellular [I]
• Used in severe thyroid storm (b/c very rapid onset) or used prior to surgery

Question 19

ADR of super saturated potassium iodide (4)

Answer 19

Rash

Rhinorrhea

Metallic taste

Swollen salivary glands

Question 20

MOA of radioactive iodine

Name 2 complications

Answer 20

• Radioactive iodine accumulates in thyroid, and radiation causes slow destruction of the gland
• Complication: Immediate thyroiditis (worsens thyrotoxicosis), eventual hypothyroidism

Question 21

Describe treatment of thyroid storm (4)

Answer 21

• Propranolol
• Glucocorticoids
• Oral KI drops
• PTU

Question 22

A patient comes in with fever, sweating, atrial fibrillation, and delirium.

What is one endocrine cause?

Answer 22

Thyroid storm