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Endocrine 2 > Kruse: thyroid drugs > Flashcards

Kruse: thyroid drugs Flashcards

1
Q

What are the thyroid agents

A
  • Levothyroxine (T4)
  • Liothyronine (T3)
  • Liotrix (4:1 ratio of T4:T3)
  • Thyroid desiccated
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2
Q

Antithyroid agents

A
  • Radioactive iodie (131 I) Sodium
  • Methimazole
  • Potassium iodide
  • Propylthiouracil (PTU)
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3
Q

What transports iodide iodide into the thyroid gland

A

NIS

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4
Q

What is an apical cell iodide transport enzyme that controls the flow of iodide across the membrane?

A

pendrin

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5
Q

where else is pendrin found? clinical implications?

A

Cochlea; if deficient or absent a syndrome of deafness and goiter called pendred syndrome occurs

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6
Q

Iodide is oxidized by what in the apical cell membrane

A

thyroidal peroxidase

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7
Q

Agents that inhibit the conversion of T4 to T3 and increase reverse T3 levels include what

A
  • Radiocontrast agents: iopanoic acid and ipodate
  • amiodarone
  • Beta blockers
  • corticosteroids

Give to those with thyroid storm

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8
Q

Drugs that decrease T4 absorption

A
  • Anacids
  • ferrous sulfate
  • cholestyramine
  • colestipol
  • ciprofloxacin
  • PPI
  • bran
  • soy
  • coffee
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9
Q

Of the T4 and T3 preparations available, what is the preparation of choice for thyroid replacement therapy and why

A
  • T4: levothyroxine

- stability, low cost, lack of allergic foreign protein, easy lab measurement, long half lift so once daily

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10
Q

Which of the antithyroid drugs is not completely absorbed and has large first pass effect

A

PTU

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11
Q

Which antithyroid is completely absorbed and has slower renal excretion than PTU

A

methimazole

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12
Q

Describe the antithyroid therapy in pregnancy

A
  • PTU in first trimester

- Methimazole in second and third

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13
Q

Toxicity of methimazole and PTU

A
  • most common: maculopapular pruriis rash at times accompanied by systemic signs such as fever, nausea, and GI distress
  • Rare: urticarial rash, vasculitis, a lupus like reaction, lymphadenopathy, hypoprothrombinemia, acute arthralgia, hepatitis (more common with PTU), and cholestatic jaundice (methimazole)
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14
Q

What are the most serious complications of PTU and methimazole

A

-agranulocytosis (<500)

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15
Q

What are the monovalent anions that block thyroid gland uptake of iodide by competitively inhibiting the iodide transport mechanism

A
  • Perchlorate
  • Pertechnetate
  • Thiocyanate
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16
Q

What is the MOA of iodides

A
  • inhibit organification and hormone release

- decrease in size and vascularity of hyperplastic thyroid glands

17
Q

Clinical use of iodide

A
  • Thyroid storm- thyrotoxic symptoms improve rapidly
  • Preoperative reduction of a hyperplastic thyroid gland
  • Block thyroidal uptake of radioactive isotopes of iodine in a radiation emergency or other exposure
18
Q

Toxicity of Iodides

A

-uncommon. Can include: acneiform rash, swollen salivary glands, mucous membrane ulcerations, conjunctivitis, metallic taste

19
Q

Iodides and pregnancy?

A

should be avoided since they can cross placenta and cause a fetal goiter

20
Q

What is the only isotope used for treatment of thyrotoxicosis

A

(131)I

21
Q

radioactive iodine is contraindicated in who

A

Pregnant women or those breast feeding

22
Q

Beta blockers and management of thyrotoxicosis

A
  • Those without sympathomimetic activity (metoprolol, propranolol, and atenolol)
  • improve symptoms but do not typically alter thyroid levels (high doses of propranolol have been shown to reduce T3 levels by about 20%)
23
Q

What Beta blocker is most commonly used

A

propanolol

24
Q

Treatment of myxedema coma

A
  • preparations given IV

- Large loading dose of T4 followed by smaller IV dosing

25
Q

Treatment of Myxedema and coronary artery disease

A

-Correction with T4 must be done cautiously to avoid provoking arrhythmia, angina, or acute MI

26
Q

Treatment of hypothyroidism and pregnancy

A
  • Women who are hypothyroid are typically infertile until restoration of normal thyroid levels
  • Maintenance of normal levels is crucial due to fetal brain development dependence on maternal T4
27
Q

When do you use antithyroid drug therapy in Graves

A
  • most useful in young patients and mild disease
  • Methimazole and PTU until remission
  • Methimazole is preferred except in pregnancy
28
Q

treatment of choice in Graves in patients with very large glands or multinodular glands

A
  • thyroidectomy

- 80-90% will require thyroid supplementation

29
Q

When do u use Radioactive iodine in Graves

A
  • most over 21
  • in pts with underlying heart disease or severe thyrotoxicosis and in elderly patients, treatment with antithyroid drugs until patient is euthyroid is preferred
30
Q

Describe the adjuncts to antithyroid therapy in Graves

A
  • B-blockers w/o sympathomimetic activity
  • these control tachycardia, HTN, and Afib
  • Diltiazem (calcium channel blocker) can be used to manage tachycardia in pts who Beta blockers are contraindicated
31
Q

Management of thyroid storm

A
  • Beta blocker to control arrhythmia
  • Potassium iodide to prevent release of thyroid hormones
  • PTU or methimazole to block hormone synthesis
  • IV hydrocortisone to protect against shock and to block conversion of T4 to T3 in peripheral tissue
  • Supportive therapy
  • in rare situations where the above is inadequate, plasmapheresis or peritoneal dialysis may be used to lower levels of T4

Endocrine 2 (10 decks)

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