Thyroid Drugs

Question 1

What is Levothyroxine (T4) used to treat?

Answer 1

Hypothyroidism

Question 2

Why is Levothyroxine (T4) the agent of choice for thyroid replacement and suppression therapy?

Answer 2

It is stable, low cost, lacks allergenic protein, and has LONG HALF LIFE permitting once daily administration.

Question 3

What is Liothyronine (T3) used to treat?

Answer 3

Hypothyroidism

Question 4

Which more potent, Levothyroxine or Liothyronine?

Answer 4

Liothyronine is 3-4 times more potent.

Question 5

Does Liothyronine have a long or short half life?

Answer 5

Short half life, requiring multiple doses.

Question 6

Is Liothyronine recommended for routine replacement therapy?

Answer 6

No.

Question 7

Which class of chemical compounds is used to treat Hyperthyroidism?

Answer 7

Thiamides

Question 8

What are the 2 thiamides used to treat hyperthyroidism?

Answer 8

Methimazole and propylthiouracil.

Question 9

Which is more potent, methimazole or propylthiouracil?

Answer 9

Methimazole is 10 times more potent.

Question 10

Is the half life of methimazole and propylthiouracil long or short?

Answer 10

Short plasma half-life.

Question 11

What is the major contraindication for Thiamides?

Answer 11

Pregnancy.

Question 12

What is the major action of Thiamides?

Answer 12

They prevent hormone synthesis by inhibiting thyroid peroxidase. They also block iodine organification.

Question 13

Do Thiamides have a fast or slow onset of action?

Answer 13

Slow because synthesis rather than release of hormones is affected. Requires depletion of T4.

Question 14

What are the adverse effects of Thiamides?

Answer 14

Nausea, GI distress. Infrequently can cause agranulocytosis.

Question 15

What is Potassium perchlorate used to treat?

Answer 15

Hyperthyroidism

Question 16

What is the action of Potassium perchlorate?

Answer 16

It is an anion inhibitor. Competitively inhibits iodide transport.

Question 17

What is the major contraindication for Potassium perchlorate?

Answer 17

It is rarely used due to its association with aplastic anemia.

Question 18

What is the action of Iodides?

Answer 18

Inhibit hormone release; inhibit organification; Decrease size and vascularity of the hyper plastic gland.

Question 19

What are the contraindications to the use of Iodides?

Answer 19

They delay onset of thioamide therapy and prevent use of radioactive iodine due to increase in iodide tissue stores. It also crosses the placenta.

Question 20

What is the action of Radioactive iodine?

Answer 20

It destroys the thyroid parenchyma.

Question 21

What is the contraindication to radioactive iodine?

Answer 21

Pregnancy.

Question 22

What is the treatment for radioactive contamination?

Answer 22

Sodium iodide. It competes out radioactive iodine.

Question 23

What is the action of Propranolol?

Answer 23

It is a beta blocker. Blocks the beta adrenergic receptor.

Question 24

What is Propranolol an effective adjunctive therapy for?

Answer 24

Thyrotoxicosis.

Question 25

What does Propranolol help alleviate?

Answer 25

It alleviates the effects of excess thyroid hormone on the heart and circulation.

Question 26

What are the effects of Propranolol?

Answer 26

Reduces breathing rate, excessive sweating, heat intolerance, nervousness and anxiety.

Question 27

True or false: Propranolol affects thyroid hormone levels.

Answer 27

False. Propranolol DOES NOT affect thyroid hormone levels.

Question 28

What is Graves disease?

Answer 28

It is the most common form of hyperthyroidism. TSH receptor activating antibodies are developed.

Question 29

What is Thyroid Storm?

Answer 29

A sudden acute exacerbation of all of the symptoms of thyrotoxicosis.

Question 30

What are the causes of Thyroid storm?

Answer 30

Discontinuing needed hyperthyroid medication; over replacement of thyroid hormone; recent treatment with radioactive iodine; severe infection, illness, or stress in a hyperthyroid patient.

Question 31

What is the treatment for Thyroid Storm?

Answer 31

Hospitalization; Decrease circulating thyroid hormone levels and decrease their formation. Use PTU or methimazole to decrease thyroid hormone. Use Na iodide or K iodide to inhibit thyroid hormone. Control heart rate by propranolol.

Question 32

Explain the hypothalamic-pituitary-thyroid axis.

Answer 32

Hypothalamus secretes thyrotropin releasing hormone (TRH). TRH stimulates synthesis and release of thyrotropin (TSH). TSH increases the synthesis and release of T4 and T3.

Question 33

What is the effect of stress on the thyroid.

Answer 33

Stress induces hypothyroidism because it is a negative regulator of the hypothalamus.