Thyroid Hormones

Question 1

Drug used to manage hypothyroidism

Answer 1

Levothyroxine

Question 2

The three primary methods for controlling hyperthyroidism are:

Answer 2

• Antithyroid drug therapy
• Destruction of the gland with radioactive iodine
• Surgical thyroidectomy

Question 3

THE THIOAMIDES: PROPYLTHIOURACIL & METHIMAZOLE

Answer 3

Propylthiouracil (PTU) and methimazole block thyroid hormone synthesis by inhibiting the peroxidase , thus blocking iodine organification, and coupling of the iodotyrosines.

• PTU also blocks peripheral deiodination of T4 to T3.
• They have no effect on thyroglobulin already stored in the gland. Therefore, clinical effects may be delayed until thyroglobulin stores are depleted.

Question 4

DOC for Graves’ disease.

Answer 4

Methimazole
• It has a longer half-life, allowing for once-daily dosing, it is efficacious at low doses and has a lower incidence of adverse effects

Question 5

When is Propylthiouracil (PTU) preferred

Answer 5

in severe hyperthyroid states or thyroid storm.

• PTU is recommended during first trimester of pregnancy due to lesser risk of teratogenic effects.

Question 6

THE THIOAMIDES: ADVERSE EFFECTS

Answer 6

Pruritic rash
Agranulocytosis
Severe hepatitis (PTU);

Question 7

IODIDE

Answer 7

• High concentrations of iodide inhibit thyroid hormone release from the gland.
• Iodide is useful in severe thyrotoxicosis and thyroid storm.
• Iodide is used prior to surgery to decrease vascularity of the thyroid gland.
• Adverse effects include sore mouth and throat, swelling of the tongue or larynx, rashes, ulcerations of mucous membranes, and metallic taste.

Question 8

• Administered orally in solution
• Its therapeutic effect is due to emission of β rays.
• Contraindicated in pregnant or nursing women, since it crosses the placenta to destroy the fetal thyroid gland and it is excreted in breast milk.

Answer 8

RADIOACTIVE IODINE (131I)

Question 9

treatment of choice for patients with very large glands or multinodular goiters.

Answer 9

• A near-total thyroidectomy
• treated with antithyroid drugs until euthyroid.
• prior to surgery, they receive a saturated solution of potassium iodide, to diminish vascularity of the gland and simplify surgery.

Question 10

ADJUNCTS TO ANTITHYROID THERAPY

Answer 10

Beta blockers

• reduce tachycardia, tremor, stare, palpitations, and anxiety
• Propranolol at high doses may reduce T3 levels by inhibiting peripheral conversion of T4 to T3.

Calcium channel blockers
- Diltiazem can be used to control tachycardia in
patients in whom β blockers are contraindicated.

Question 11

THYROID STORM

Answer 11

severe clinical manifestations of thyrotoxicosis

• Precipitating factors include: infections, stress, trauma, thyroidal or nonthyroidal surgery, diabetic ketoacidosis, labor, and heart disease.

Question 12

THYROID STORM: THERAPEUTIC REGIMEN

Answer 12

Question 13

Drug that Block iodide uptake

Answer 13

Perchlorate, thiocyanate, nitrate

Question 14

Block organification of iodine

Answer 14

Thioamides, thiocyanate, sulfonamides

Question 15

Block coupling reaction

Answer 15

Sulfonamides, thioamides

Question 16

Block hormone synthesis & release

Answer 16

Lithium, iodide

Question 17

Block peripheral conversion of T4 to T3

Answer 17

PTU, amiodarone

Question 18

Increase rate of liver metabolism

Answer 18

Phenobarbital, rifampin, carbamazepine, phenytoin

Question 19

complications of amiodarone therapy.

Answer 19

Causes both hypo and hyperthyroidism

Question 20

AMIODARONE-ASSOCIATED HYPOTHYROIDISM (AIH)

Answer 20

A large amount of ingested iodine inhibits thyroid hormone synthesis

Thyroid function can be normalized with
levothyroxine if amiodarone cannot be stopped.

Question 21

AMIODARONE-ASSOCIATED HYPERTHYROIDISM (AIT)

Type 1

Answer 21

• There is increased synthesis of T4 and T3 due to iodine from amiodarone.
• Occurs in patients with preexisting goiter.
• Treated with high dose methimazole or propylthiouracil.

Question 22

AMIODARONE-ASSOCIATED HYPERTHYROIDISM (AIT)

Type 2

Answer 22

• Destructive thyroiditis results in excess release of T4 and T3.
• Typically occurs in euthyroid patients.
• Caused by direct toxic effect of amiodarone on thyroid follicular epithelial cells. Treated with glucocorticoids.