Thyroid and Antithyroid Drugs

Question 1

dopamine agonists cause an ↑ / ↓ in GH

Answer 1

↓

Question 2

iodide ion is taken in to the thyroid gland via ______ (transporter)

Answer 2

Na/I symport

Question 3

T3/T4 is more potent

Answer 3

T3

Question 4

thyroid hormones are metabolized by:

• deiodinization (most important)
• ______
• _______

Answer 4

glucorondiation and sulfation

Question 5

the use of propylthiouracil can inhibit ________ (enzyme) and can low T3 levels

Answer 5

5’ deiodinase enzyme

Question 6

what drugs can cause low T3 levels by inhibiting 5’ deiodinase?

Answer 6

• propylthioruacil
• propranolol
• corticosteroids
• amiodarone

Question 7

of the enzymes that metabolize thyroid hormones, which ones are inducible?

Answer 7

• deiodinase

- UDP glucuronosyltransferase

Question 8

_______ is the most common cause of hypothyroidism in the US and _______ is the most common cause worldwide

Answer 8

Hashimoto’s = US

iodine deficiency = worldwide

Question 9

lithium can cause _____thyroidism

Answer 9

hypothyroidism

Question 10

_______ is the hormone preparation of choice for thyroid hormone replacement therapy

Answer 10

synthetic levothyroxine (T4)

Question 11

cardinal features of myxedema coma include: (3)

how would you treat these patients

Answer 11

• hypothermia
• respiratory depression
• ↓ consciousness

seen in severe and long standing form of HYPOthyroidism

give them T3 and T4 via IV

Question 12

↑ estrogen will lead to ↓/ ↑ serum levels of thyroid hormones

Answer 12

↓; because estrogen ↑’s the serum concentration of thyroxin binding globulin (TBG)

Question 13

what are 3 reasons you would give a higher dose of synthetic T4 in pregnant patients?

Answer 13

1. estrogen induces and ↑ concentration fo TBG
2. expression of 5’ deiodinase by placenta
3. small amount passes from mother to uterus

Question 14

what sit he treatment plan for a patient with congenital hypothyroidism

Answer 14

must administer early and quickly to prevent long term effects; 
if levothyroxine (synthetic T4) is given within the first 2 weeks of life, normal physical and mental development can be achieved.

Question 15

thioamides such as _______ and propylthiouracil inhibit the_________ enzyme in the thyroid

Answer 15

• methimazole

Thioperoxidase enzyme (TPO) 
- inhibit the formation of thyroid hormones

Question 16

of the thioamides, why is ________ preferred over the other in treatment of severe hyperthyroid and thyroid storm?

Answer 16

propylthiouracil because it also partially inhibits the peripheral dedication of T4 to T3 (methimazole does NOT)

Question 17

of the thoamides which one is more teratogenic?

Answer 17

methimazole

Question 18

what are the adverse effects seen with thioamides?

which one is most common and which is the most serious?

Answer 18

• urticarial rash (most common)
• agranulocytosis (most serious)
• hepatotoxicity
• vasculitis
• teratogenicity

Question 19

methimazole is preferred over PTU except in ________

Answer 19

first trimester of pregnancy and thyroid storm

Question 20

which of the thioamides is more hepatotoxic?

Answer 20

Propylthiouracil (PTU)

Question 21

what is the effect of iodides in treating thyroid conditions?

Answer 21

iodides cause the thyroid gland to shut down;

used to treat thyroid storm, preoperative preparation for surgery of the thyroid and radiation emergencies involving release of radioactive iodine

Question 22

how does hyperthyroidism cause catecholamine excess like manifestations such as HTN, tachycardia, lid lag, sweating, etc even though catecholamine levels are NOT increased

Answer 22

• they ↑ the expression of β adrenergic receptors

Question 23

_______ (drug family) is used to treat the “catecholamine excess like” manifestations

Answer 23

β blockers

Question 24

what is your β blocker of choice in a thyroid storm

Answer 24

propanolol; it has peripheral inhibition of deiodinization of T4 to T3 (like PTU)

Question 25

in a patient whom β blockers are contraindicated, what 2 drugs can be used to control tachycardia?

Answer 25

• diltiazem
• verapamil
  (non dihydropyradine calcium channel blocking agents)

β blockers can be contradicted in COPD patients

Question 26

glucocorticoids MOA and use

Answer 26

inhibits the peripheral conversion of T4 to T3 and promotes vasomotor stability

useful in thyroid storm

Question 27

how do bile acid sequestrates help treat thyroid storm?

Answer 27

cholestyramine and other bile acid sequestrates bind to and prevent the enterohepatic cycling of thyroid hormones

Question 28

________ is the preferred treatment for HYPERthyroidism

Answer 28

radioiodine therapy; it destroys the thyroid parenchyma

Question 29

a patient with hyperthyroidism develops an infection causing an acute exacerbation of hyperthyroidism. what would you give to treat this patient

Answer 29

diagnosis: thyroid storm (4P’s + bile acid sequestrate)

• PTU
• Potassium iodides
• propranolol
• prednisone (corticosteroids)
• bile acid sequestrants

Question 30

in treating thyrotoxicosis in pregnancy, _______ is given in the first trimester of pregnancy and then _____ is given for the remainder of the pregnancy to avoid _________

Answer 30

1st trimester: PTU

2nd trimester: Methimazole to avoid potential liver damage

Question 31

a person taking amiodarone shows symptoms of hyperthyroidism. panel shows ↓ TSH and ↑ T4 and T3.
what are the two types of thyrotoxicosis that can be caused by amiodarone and how can you tell the differenced?

Answer 31

• ↑ synthesis of thyroid hormones
• destructive thyroiditis

do a reactive iodine uptake: 1st type where there is ↑ synthesis will show uptake of the iodine but the destructive type will not take it up.
lab values are the same for both types

Question 32

a person taking amiodarone has ↓ TSH and ↑ T4 and T3. the did NOT take up the radioactive iodine when administered. what do you give to treat his condition

Answer 32

destructive thyroiditis caused by amiodarone

treat with GLUCOCORTICOIDS

Question 33

_________ (drugs) are given to treat amiodarone induced thyrotoxicosis where there is ↑ synthesis of thyroid hormones

Answer 33

anti-thyroid hormones

Question 34

pretibial myxedema is a clinical feature of what thyroid pathology

Answer 34

grave’s disease

Question 35

scalloped colloid on histology of thyroid. what type of HS reaction is this disease

Answer 35

dx: Grave’s

Type 2 HS

Question 36

anti-thyroglobulin antibodies and anti-thyroid peroxidase (TPO) antibodies are found in a patient. what is a likely complication of this condition

Answer 36

dx. Hashimoto’s
↑ risk for developing other autoimmune conditions: DM1, SLE, myasthenia gravis, pernicious anemia

↑ risk for B cell lymphoma (MALToma)

Question 37

what is the Wolf Chaikoff effect?

Answer 37

High-dose iodide blocks the release of T4 and T3 into circulation and transiently inhibits thyroid hormone synthesis by blocking the organification step

Question 38

which drugs most commonly can HYPOthyroidism

Answer 38

• sulfonamides
• lithe
• amiodarone

Question 39

sulfonylureas can cause ___thyroidism

Answer 39

hypothyroidism

Question 40

tyrosine kinase inhibitors can cause _____thyroidism

Answer 40

hypothyroidism