Thyroid

Question 0

T3 drug form, active metabolite, limited specialized uses

Answer 0

Liothyronine

Question 1

T4 drug form, most replacement uses

Answer 1

Levothyroxine

Question 2

Thiamine, peroxidase inhibitor, effective once daily

Answer 2

Methimazole

Question 3

Thioamide, peroxidase inhibitor, many specific uses

Answer 3

Propylthiouricil

Question 4

Prior to thyroidectomy, for thyroid storm, for radiation emergencies

Answer 4

Iodides

Question 6

Alternative to surgery for destruction of thyroid

Answer 6

Radioactive iodide

Question 7

T3 or T4: What is 5x more potent?

Answer 7

T3

Question 8

T3 or T4: What is more rapidly metabolized?

Answer 8

T3. T4 is more protein bound so slows degradation

Question 9

Levothyroxine has (SLOW/FAST) onset and (SHORT/LONG) duration?

Answer 9

Slow, Long. Converted to more active T3 in body.

Question 10

T/F: Levothyroxine (T4) given IV is preferred even in myxedema coma, due to its more predictable effects on patients?

Answer 10

True

Question 11

T/F: Switching brands of levothyroxine should be avoided.

Answer 11

True- due to differences

Question 12

What is rarely used in chronic therapy of hypothyroidism due to rapid onset, too-marked effects, and too-short half life?

Answer 12

Liothyronine

Question 13

When is liothyronine indicated?

Answer 13

• Has specific and limited indications.
• In thyroid cancer, for maintaining supressive effects while patients are tapered off of T4 prior to surgery and for the more rapid onset while T4 takes effect after surgery.
• For similar short term support prior to and following radioiodine.

Question 14

Levothyroxine and liothyronine can be given ______.

Answer 14

Orally

Question 15

Side effects of levothyroxine and liothyronine?

Answer 15

Minor- generally overdose leading to hyperthyroidism

Question 16

What can alter thyroid function and/or TH absorption?

Answer 16

Numerous drugs along with effecting protein binding and metabolism.
-Physiological status and/or other diseases also can change TH effectiveness and may require dosage adjustments.

Question 17

Symptomatic relief for hyperthyroidism includes…

Answer 17

Propranolo or diltiazem to treat symptoms primarily due to sympathetic nervous system stimulation

Question 18

Disease modifying treatments of hyperthyroidism

Answer 18

Anti-thyroid drugs: Thioamides, iodides

Thyroid gland ablation: Therapeutic radioiodine, partial thyroidectomy

Question 19

List 2 thioamides and their MOA

Answer 19

Propylthiouracil and Methimazole.

• Inhibit peroxidase enzyme, both iodination and coupling steps.
• Do not block release of preformed THs, therefore exhibit a latent period of weeks before colloid is depleted of stored TH.
• May have direct anti-autoimmune effects as well

Question 20

What also inhibits peripheral conversion of T4 to T3, therefore more rapid effect, so it is preferred in treating thyroid storm?

Answer 20

Propylthiouracil

Question 21

Therapeutic use of Thioamides (Propylthiouracil and Methimazole)

Answer 21

Non-destructive

• Useful for immediate control of thyroid hormone production.
• Average therapy about 1 year, but disease remission in only 30% of pts.
• Radioiodine or surgery required if relapse occurs after thioamides.

Question 22

How are thioamides (Propylthiouracil and Methimazole) taken? Concentrated? Metabolized?

Answer 22

Orally,
Cleared from circulation and concentrated in thyroid.
Metabolism by conjugation and excretion in urine.

Question 23

Propylthiouracil or Methimazole? Which is more potent?

Answer 23

Methimazole

Question 24

Propylthiouracil or Methimazole? Short half life and must be given 2-4 times/day

Answer 24

Propylthiouracil

Question 25

T/F: The 10x higher potency of methimazole is a significant advantage?

Answer 25

False: is not | -Longer duration is important because helps with compliance

Question 26

Adverse effects of both Propylthiouracil and Methimazole?

Answer 26

- Agranulocytosis: rare, can be fatal, usually in 1st few months, symptoms of sore throat and fever, immediately discontinue use, dont use thioamide in patient again. - Skin rash, drug fever, arthralgia, myalgia, others. - Hypothyroidism if dose too high

Question 27

Propylthiouracil or Methimazole? Which causes liver toxicity/failure?

Answer 27

Propylthiouracil- a reason why Methimazole is preferred drug along with the longer duration of action.

Question 28

When is Propylthiouracil indicated?

Answer 28

- Pregnancy and breast feeding. | - Thyroid storm

Question 29

Potassium iodide, sodium iodide, and molecular iodide are given orally as solutions or tablets in hyperthyroidism and are examples of what?

Answer 29

Iodides

Question 30

Pharmacologic effects of Iodides

Answer 30

- Acute inhibition of synthesis and release of THs; no effect on T4-->T3 conversion. - Decrease size and vascularity of thyroid gland.

Question 31

Therapeutic uses of iodides

Answer 31

- During thyroid storm, to inhibit synthesis and release of THs; effect is rapid but of short duration, so iodides not useful for long term treatment. - During last 10 days before thyroidectomy, to make cleaner safer surgery. - Used in radiation emergencies, eg: nuclear power plant accidents, to intentionally compete with released radioactive iodine.

Question 32

T/F: Iodides should be used prior to radioiodine therapy?

Answer 32

False- should not be used because they would compete for uptake.

Question 33

Side effects of iodides:

Answer 33

Mild: sore throat, burning mouth, rash, diarrhea

Question 34

What are present in foods such as cabbage and turnips and act s natural "goitrogens"?

Answer 34

Iodides

Question 35

Radioactive Iodine: 1) Isotope used? 2) Half life= ____days 3) 85% weak ____ radiation (travels 1-2 mm in tissue); useful for localized tissue destruction. 4) 15% stronger _______ radiation; useful for diagnosis.

Answer 35

A) 131 I B) 8 C) Beta d) Gamma

Question 36

1) Small doses of radioiodine are used for what? | 2) Large doses of radioiodine are used for what?

Answer 36

1) Tracer studies of uptake for diagnosis of hyperthyroidism, assessment of anatomy and function of thyroid tissue, and localization of metastatic thyroid cancer. 2) Destruction of thyroid tissue. Given orally as solution or capsules; concentrated in gland.

Question 37

Radioiodine is contraindicated in...

Answer 37

Pregnancy, nursing and young children

Question 38

High doses of radioiodine can cause what?

Answer 38

Radiation thyroiditis and salivary adenitis

Question 39

Treatment of choice for hyperthyroidsim in: A) Young B) Older C) Pregnant

Answer 39

A- Methimazole B- Radioactive iodine C- Propylthiouracil