Pharmacology of Thyroid & Anti-Thyroid Drugs

Question 1

This enzyme produces the metabolically inactive rT3 and is most prevalent in the placent.

Answer 1

D3

Question 2

What are the indications for iodide salts and iodine?

Answer 2

Management of thyroid storm and thyroidectomy

Question 3

What severe ADR is associated with Propylthiouracil (PTU)?

Answer 3

Severe hepatitis or liver failure

Question 4

What is the MOA of Propylthiouracil (PTU) and methimazole?

Answer 4

Inhibits the thyroid peroxidase to inhibit TH synthesis

Question 5

What is the MOA of Lugol’s solution and SSKI?

Answer 5

They trigger the Wolff-Chaikoff effect by increasing blood iodide. This decreased TH synthesis by the the thyroid

Question 6

This drug is the preferred initial therapy for patients with myxedma due to thyroid pathology.

Answer 6

Liothyronine

Question 7

This drug is a synthetic form of T4. When should patients take the medication?

Answer 7

Levothyroxine - best absorbed on an empty stomach

Question 8

Levothyroxine must be started in low doses in vulnerable patient populations. Why is this?

Answer 8

The drug rapidly increases BMR. Older patients, patients with CVD, and patients with severe hypothyroidism cannot adjust their cardiac function quickly enough to support the increased BMR.

Question 9

True/False. Thyroid hormone carries out its effects via DNA binding and modulation of gene expression.

Answer 9

True

Question 10

How does Propylthiouracil (PTU) differ from methimazole with regard to MOA?

Answer 10

Both drugs inhibit TH synthesis, but PTU also inhibits conversion of T4 to T3 in the periphery

Question 11

This enzyme coverts T4 to T3, but is isolated to the brain, heart, and other organs that must function even during periods of starvation.

Answer 11

D2

Question 12

Corticosteroids must be given before thryoid hormone treatment in patients with secondary hypothyroidism. Why is this?

Answer 12

Secondary hypothyroidism is due to pituitary insufficiency. Because of this, levels of glucocorticoids are also low. Administration of TH will increase BMR to a point that the low levels of glucocorticoids are no longer sufficient

Question 13

This drug is the most commonly used adjunctive therapy to treat symptoms associated with hyperthyroidism.

Answer 13

Propanolol - also inhibits peripheral conversion of T4 to T3

Question 14

This drug is a permanent cure for hyperthyroidism, but also a leading cause of hypothyroidism.

Answer 14

Radioactive Iodine (131I)

Question 15

This drug is a synthetic form of T3.

Answer 15

Liothyronine

Question 16

This drug should be used during the first trimester of pregnancy.

Answer 16

Propylthiouracil (PTU) - switch to methimazole after the first trimester

Question 17

Nearly all thyroid hormone is transported in the blood via what protein?

Answer 17

Thyroxine binding globulin (TBG)

Question 18

This is the preferred drug to treat patients with hyperthyroidism.

Answer 18

Methimazole

Question 19

Why should patients receive anti-thyroid therapy before a thyroidectomy?

Answer 19

The thyroid is a highly vascular organ. Administration of anti-thyroid medications reduces TH synthesis and thus thyroid vascularity and size. This reduces the risk of operative complications

Question 20

True/False. Methimazle inhibits peripheral conversion of T4 to T3.

Answer 20

False - this is a mechanism of Propylthiouracil (PTU)

Question 21

What severe ADR is associated with methimazole?

Answer 21

Agranulocytosis