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Endocrine Two > Kruse - Thyroid and Antithyroid Drugs DSA > Flashcards

Kruse - Thyroid and Antithyroid Drugs DSA Flashcards

1
Q

Longer half life: T4 or T3? Which is more potent?

A

T4 (7 days) > T3 (1 day).

T3 is more potent, but T4 is preferred therapy for hypothyroidism as thyroid replacement.

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2
Q

T4 and T3 absorption may be affected by myxedema with ileus, but not by mild ____?

A

hypothyroidism

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3
Q

Agents that inhibit conversion of T4 to T3 (via inhibition of 5’-deiodinase in cytoplasm) and increase reverse-T3 (inactive) levels.

A

Radiocontrast agents iopanoic acid and ipodanate

***Amiodarone, B-blockers, Corticosteroids

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4
Q

Patients experiencing ____ are administered agents that inhibit T4 to T3 conversion to reduce T3 levels?

A

Thyroid storm (thyrotoxic crisis)

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5
Q

What drugs decrease T4 absorption?

What instructions should be given to someone who is taking T4?

A

Cholestyramine, colestipol, cipirofloxin, PPI, ferrous sulfate, bran, soy, coffee, antacids (aluminum hydroxide, calcium carbonate)
-Instruct to take on an empty stomach

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6
Q

Drugs that induce hepatic CYP450s, thus increasing metabolism of T4 and T3 are ____.

A

Rifampin, rifabutin, phenobarbital, carbamazepine, phenytoin, imatinib, protease inhibitors

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7
Q

Advantages of T4 (levothyroxine) for thyroid replacement therapy

A

Stability, low cost, lack of allergic foreign protein, easy lab measurement of serum levels, long 1/2 life –> 1x/day dose

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8
Q

Agents that interfere with production of thyroid hormone

A
  • Thioamides (block iodide organification/oxidation in the thyroid)
  • Anion inhibitors (block thyroid uptake of iodide)
  • Iodide (inhibit organification, decrease size/vascularity of gland)
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9
Q

Agents that modify tissue response to thyroid hormone

A

?

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10
Q

Thyroid gland destruction with radiation or surgery

A

Radioactive iodine

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11
Q

Name the thioamides and function.

A

Methimazole, Propylthiouracil (PTU)

Used for hyperthyroidism

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12
Q

MOA of methimazole and Propylthiouracil (PTU)

A

Inhibit thyroidal peroxidase-catalyzed reactions and BLOCKS IODIDE ORGANIFICATION (Inhibit TH synthesis by blocking oxidation of iodide in the thyroid gland.)

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13
Q

Two pregnant woman have hyperthyroidism and need agents that interfere with production of thyroid hormone. One is in her 1st trimester, one is in her 2nd/3rd trimester. What drug is given to each?

A

1st trimester, give PTU

2nd/3rd trimester, give methimazole

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14
Q

Methimazole and Propylthiouracil (PTU) - half lives and dosing.

A

Methimazole - half life = 6hrs; 1x/day dose

Propylthiouracil (PTU) - half life = 1.5 hours; 3-4x/day dose

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15
Q

How does PTU MOA differ from methimazole?

A

PTU blocks peripheral conversion of T4 to T3, allowing for a significantly greater fall in T3 concentration.

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16
Q

Most common adverse effects of methimazole and propylthiouracil (PTU).

A

Maculopapular pruritic rash with possible fever, nausea, GI distress

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17
Q

Adverse effect that is more common in PTU than methimazole?

A

Hepatitis

18
Q

Adverse effect that’s more common in methimazole than PTU?

A

Cholestatic jaundice

19
Q

Most serious adverse effect of methimazole and propylthiouracil (PTU).

A

Agranulocytosis (

20
Q

Treatment for agranulocytosis induced by PTU or methimazole.

A

Discontinue drug and give colony-stimulating factor (pegfilgrastim or filgrastim).

21
Q

What population (taking thioamide) has especially increased risk for agranulocytosis?

A

Especially in older patients receiving high dose methimazole

22
Q

MOA of anion inhibitors (perchlorate, pertechnetate, thiocynate)

A

Block thyroid uptake of iodide by competitive inhibition of iodidie transport.

23
Q

MOA of iodides.

A

Inhibit organification and hormones release, decreases size and vascularity of the hyperplastic thyroid gland.

24
Q

In what three clinical settings would iodide be of use for a person with hyperthyroidism?

A
  1. Thyroid storm
  2. Pre-operative reduction of hyperplastic thyroid gland
  3. Block thyroidal uptake of radioactive isotopes of iodine in radiation emergency or exposure to radioactive iodine.
25
Q

Mother did not stop taking iodide for her hyperthyroidism and it crossed the placenta. What would the fetus present with?

A

Fetal goiter

26
Q

A person presents with an acneiform rash, swollen salivary glands, mucous membrane ulcerations, conjuctivitis, and metallic taste - what are they on?

A

Iodide for hyperthyroidism

27
Q

What is the MOA of radioactive iodine?

A

It is rapidly absorbed and concentrated by the thyroid and incorporated into the follicles where the B-radiation destroys thyroid parenchyma.

28
Q

Evidence of radioactive iodine B-radiation destroying thyroid parenchyma.

A

epithelial swelling and necrosis, follicular disruption, edema, leukocyte infiltration

29
Q

Advantages of radioactive iodine treatment.

A

Ease of administration, effectiveness, low expense, absence of pain (no surgery).

30
Q

Administration of of radioactive iodine treatment is contraindicated in what type of people?

A

pregnant women or those breastfeeding

31
Q

What types of B-blockers are effective in management of thyrotoxicosis?

A

Those without sympathomimetic activity - metoprolol, PROPANOLOL, atenolol

32
Q

What is the result of B-blocker use?

A

Improves symptoms of hyperthyroid but does not typically alter thyroid levels.

33
Q

DOC for hypothyroidism - both for (1) replacement therapy and (2) drug-induced hypothyroid that is not alleviated stoppage of offending agent.

A

Levothyroxine (T4)

34
Q

A person presents with progressive weakness, stupor, hypothermia, hypoventilation, hypoglycemia, hyponatremia, water intoxication, shock, and death. What is this and what do you treat with?

A

Myxedema coma (end state of untreated hypothyroidism), treat with IV Levothyroxine (large loading dose, then smaller dosing).

35
Q

Treatment of myxedema coma with T4 for someone with what ___ concomitant condition must be taken into account.

A

Coronary artery disease - T4 can provoke arrhythmia, angina, and acute MI

36
Q

A woman wants to conceive, but cannot. What could be the cause and what is cruicial to make sure is administered once she becomes pregnant?

A

If hypothyroid, women are typically infertile until normal thyroid levels restored.
Maternal T4 crucial for fetal brain development.

37
Q

Potential treatments for Grave’s Disease (hyperthyroid)

A
  1. Antithyroid therapy - TxOC in young pts with small glands and mild dz; methimazole preferred over PTU)
  2. Thyroidectomy - TxOC for pts with large glands or multinodular goiter)
  3. Radioactive iodine - TxOC for most people over 21
  4. Adjunct tx - B-blockers to control tachycardia, HTN, afib.
38
Q

TxOC in young pts with Graves with small glands and mild dz

A

Antithyroid therapy

39
Q

TxOC for pts with large glands or multinodular goiter.

A

Thyroidectomy

*80-90% will require replacement therapy

40
Q

TxOC for most people over 21, esp those with underlying heart disaese, severe thyrotoxicosis, or elderly.

A

Radioactive iodine

*80% will require replacement therapy

41
Q

A person is taking antithyroid therapy, but needs adjunct to control tachycardia and B-blockers are CI. What drug can be used?

A

diltiazem (Ca-channel blocker)

42
Q

Tx regimen for thyrotoxicosis

A
  1. B-blocker for arrhythmia
  2. Potassium iodide - prevent TH release from gland
  3. IV hydrocortisone - protect from shock and decraese T4 to T3 converstion in peripheral tissues/blood
  4. Potentially plasmapharesis or peritoneal dialysis to lower T4 levels.

Endocrine Two (16 decks)

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