Thyroid Drugs

Question 1

What is the pathway for thyroid hormones being released onto the target tissue? (5 steps)

Answer 1

CNS → Hypothalamus (TRH) → Pituitary (TSH) → Thyroid (T3/T4) → Target tissue

Question 2

T3 and T4 provide negative feedback to what?

Answer 2

Pituitary and hypothalamus

Question 3

Thyroid hormones are regulated by what 2 things?

Answer 3

TSH and iodide

high iodide will block thyroid hormone production

Question 4

How do thyroid hormones affect BMR?

Answer 4

Increase

Question 5

Due to the fact that thyroid hormones are important for growth/ maturation (including CNS), hypothyroidism in children is concerning because it can lead to what?

Answer 5

Cretinism

Question 6

Is T3 or T4 more effective and why?

Answer 6

T3

Question 7

What type of receptors do T3 and T4 act through?

Answer 7

Nuclear receptors (slow effect in body)

Question 8

Myxedema is hypo or hyperthyroidism?

Answer 8

Hypothyroidism

myxedema coma = severe hypothyroidism

Question 9

Do you have high or low levels of TSH with hypothyroidism?

Answer 9

High (primary cause of thyroid gland failure)

Question 10

Pt presents with slow BMR, hypothermia (cold intolerance), fatigue +/- goiter. What are you concerned for?

Answer 10

Hypothyroidism

Question 11

Pt presents with fast BMR, tachycardia, fatigue, hot (heat intolerant), tremor, insomnia, and diarrhea. What are you concerned for?

Answer 11

Hyperthyroidism

Question 12

What are the 2 most common causes of hyperthyroidism?

Answer 12

Grave’s disease and toxic nodular goiter

Grave’s = autoimmune disease, activate Ab to TSH receptor

Question 13

What are the treatment options for hyperthyroidism? (3)

Answer 13

Surgery, decrease T4/T3, block sxs with beta-blockers

Question 14

Propranolol and metoprolol drug class?

Answer 14

Beta-adrenergic blocking agents

Question 15

Levothyroxine drug class?

Answer 15

Thyroid hormone replacement

Question 16

Liothyronine sodium drug class?

Answer 16

Thyroid hormone replacement

Question 17

Desiccated thyroid drug class?

Answer 17

Thyroid hormone replacement

Question 18

Methimazole drug class?

Answer 18

Thioamides

Question 19

What do thioamides do?

Answer 19

Inhibit thyroid hormone synthesis

Question 20

Propylthiouracil (PTU) drug class?

Answer 20

Thioamides

Question 21

Iodide drug class?

Answer 21

Thioamides

Question 22

Radioactive iodine (131 I) drug class?

Answer 22

Thioamides

Question 23

What is the MOA for Levothyroxine?

Answer 23

T4- produces N levels of T3/T4 (carefully titrated to individual)

Question 24

What is the DOC for hypothyroidism?

Answer 24

Levothyroxine

Question 25

What are the important pharmacokinetic properties of Levothyroxine?

Answer 25

t1/2 = 7 days = ~5 weeks for steady state

Question 26

What is the MOA for Liothyronine?

Answer 26

T3

Question 27

When is Liothyronine used?

Answer 27

Initial hypothyroid treatment (not maintenance)

Question 28

What are the important pharmacokinetic properties of Liothyronine?

Answer 28

t1/2 = 24 hours, shorter duration (than T4)

Question 29

What is the MOA for Desiccated thyroid?

Answer 29

Mix of T4 and T3 from pigs

Question 30

When is Desiccated thyroid used?

Answer 30

Hypothyroid (pts with deficiency in peripheral deiodinase enzyme)

Question 31

What are the SEs for all thyroid hormone replacement drugs?

Answer 31

Hyperthyroidism | fast BMR, tachycardia, fatigue, hot (heat intolerant), tremor, insomnia, and diarrhea

Question 32

What is the MOA for Propylthiouracil (PTU)?

Answer 32

Blocks conversion of T4 to T3

Question 33

When is Propylthiouracil (PTU) used?

Answer 33

Hyperthyroid if allergic to Methimazole or pregnant

Question 34

What are the contraindications for Propylthiouracil (PTU)?

Answer 34

Severe liver injury, acute liver failure (black box warning) Only use low doses in pregnancy

Question 35

What is the MOA for Methimazole?

Answer 35

Potent inhibitor of T4 synthesis

Question 36

What is the DOC for hyperthyroid?

Answer 36

Methimazole (unless allergic or pregnant, then use PTU)

Question 37

What is the 1st line treatment for Grave's disease? (2)

Answer 37

Methimazole and PTU | use with beta blocker because effects are gradual as circulating T3/T4 levels last about a week

Question 38

What are the SEs of Methimazole and PTU? (4)

Answer 38

Itching, skin rash, reversible granulocytopenia/ agranulocytosis, goiter

Question 39

What is the MOA for iodide?

Answer 39

Decreases synthesis and release of T4/T3 (short term effect ~2-8 weeks)

Question 40

When specifically is iodide used in the treatment of hyperthyroid?

Answer 40

7-10 days prior to surgery (to prevent thyroid storm) and radioactive emergencies (competes with radioactive iodide to prevent binding)

Question 41

What is the MOA for Radioactive iodine (131 I)?

Answer 41

Taken into gland specifically

Question 42

What is the use of Radioactive iodine (131 I) in small amounts (µCi)?

Answer 42

Diagnostic

Question 43

What is the use of Radioactive iodine (131 I) in large amounts (mCi)?

Answer 43

Gland destruction

Question 44

In patients where surgery for the treatment of hyperthyroid is indicated but cannot be tolerated, what drug should be used?

Answer 44

Radioactive iodine (131 I)

Question 45

What is the definitive pharmacologic treatment for Grave's?

Answer 45

Radioactive iodine (131 I)

Question 46

What is the preferred treatment for toxic nodular goiter?

Answer 46

Radioactive iodine (131 I)

Question 47

What are the SEs of Radioactive iodine (131 I)? (2)

Answer 47

Thyroid storm (decrease risk with thioamide), can cause hypothyroidism over time

Question 48

What are the contraindications to Radioactive iodine (131 I)? (3)

Answer 48

Pregnancy, nursing, mother's who lack childcare

Question 49

What is the MOA for propranolol and metoprolol?

Answer 49

Non-specific beta blockers

Question 50

What is the preferred beta blocker and why?

Answer 50

Propranolol (also inhibits peripheral conversion of T4 to T3)

Question 51

What is the use of propranolol and metoprolol?

Answer 51

Decrease sxs of hyperthyroidism

Question 52

What is the contraindication to propranolol and metoprolol?

Answer 52

Asthma (use CCBs instead)