Hypothyroidism Pharmacology

Question 1

Most common cause of hypothyroidism

Answer 1

chronic autoimmune thyroiditis (Hashimoto’s thyroiditis)

Question 2

Pharmacology of levothyroxine

Answer 2

snythetic preparation of T4 → converts to T3 intracellularly

Question 3

How should levothyroxine be taken for best absorption?

Answer 3

on empty stomach

Question 4

How long does it take Levothyroxine to reach steady state?

Answer 4

28 days (4*half life)

Question 5

what is the difference between the multiple brands of levothyroxine?

Answer 5

varying bioavailability → slight changes in T4

Question 6

How should you treat a patient with levothyroxine to avoid variations?

Answer 6

continue patient on the same product

Question 7

How should you dose levothyroxine in patients with CVD and the elderly?

Answer 7

“start low and go slow”

Question 8

What levels will guide your dose adjustments of levothyroxine?

Answer 8

TSH and T4

Question 9

adverse effects of levothyroxine

Answer 9

heart failure, angina, myocardial infarction
allergic or idiosyncratic reactions
osteoporosis

Question 10

If you suspect your patient is allergic to thyroid hormone replacement what would you want to prescribe her?

Answer 10

Synthroid

Question 11

Levothyroxine will interfere with drugs that:

Answer 11

interfere with T4 absoprtion from the gut
increases T4 clearance
blcok conversion of T4 → T3

Question 12

What food/drink should a patient avoid when taking their dose of levothyroxine?

Answer 12

those with high fiber, soy, iron

coffee or milk

Question 13

How long should you separate levothyroxine and interacting binding medications?

Answer 13

4 hours apart

Question 14

How does liothyronine (T3) compare to levothyroxine?

Answer 14

3-4 times more potent

Question 15

Why is liothyronine (T3) not recommended as routine replacement?

Answer 15

short half life
difficulty monitoring
more expensive
avoid in patients with cardiac disease

Question 16

Who is the only population that uses liothyronin (T3)?

Answer 16

patients with polymorphism in D2 gene who are symptomatic on T4 alone

Question 17

What lab values would have patient with subclinical hypothyroidism have?

Answer 17

normal free T4 and mildly elevated serum TSH → without obvious symptoms

Question 18

When should you treat a patient with subclinical hypothyroidism?

Answer 18

TSH levels > 10
increased risk of devloping overt hypothyroidism if anti-thyroid peroxidase antibodies (TPOAb) are present
potential cardiac benefit in treating

Question 19

What do you treat a patient with subclinical hypothyroidism with?

Answer 19

levothyroxine

Question 20

If your hypothyroid patient becomes pregnant what should you do with her meds?

Answer 20

increase dose of levothyroxine ASAP → avoid overt hypothyroidism and adverse outcomes

Question 21

Reference ranges for TSH and serum T4 will depend on

Answer 21

specific trimester in pregnancy

Question 22

Signs and symptoms of myxedema coma

Answer 22

hypothermia, advanced stages of hypothyroid symptoms, alterd sensorium, hypoglycemia, hypoventilation

Question 23

What underlying dissorders may be associated with myxedema coma?

Answer 23

CAD or sepsis

Question 24

In myexdema coma how should the medications be administered to the patient?

Answer 24

parental only → no GI perstalsis

Question 25

Goals of treating myxedema coma

Answer 25

regain consciousness
lower TSH concentrations
improve vitals

Question 26

Initial therapies of myexdema coma

Answer 26

levothyroxine
liothyronine
hydrocortisone
supportive therapy [ventilation, BP, temperature, glycemic]
treat underlying disorder