Thyroid Flashcards

1
Q

Free T4

A

active form as most is bound to protein

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2
Q

What is myxedema coma?

A

when hypothyroidism decompensates’ life threatening emergency IV thyroid hormone should be administered

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3
Q

How often should free T4 and TSH be checked in hypothyroidism

A

every 6 to 8 weeks until normalized then 6 months later then yearly

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4
Q

what drugs are associated with causing hypothyroidism?

A

amiodarone interferons llithium nitroprusside TKIs (sunitinib)

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5
Q

levothyroxine is a pregnancy ___

A

A; increases of 30 to 50% may be necessary during pregnancy

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6
Q

when should thryoid hormone replacement be taken?

A

first thing in the morning; empty stomach at least 30 mins before breakfast

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7
Q

What can be taken after exposure to radiation to prevent an accumulation of radioactive iodine?

A

potassium iodide

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8
Q

liothyronine

A

T3

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9
Q

dessicated thyroid

A

T3 and T4 Armour Thyroid; dosed in grains

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10
Q

How is levothyroxine dosed initially?

A

in patients > 50 or in patients <50 with underlying cardiac diseasestart at 50mcg/d

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11
Q

in patients >50 with cardiac disease what is the start dose of levothyroxine

A

start at 12.5mcg/ day; titrate every 4 to 8w to 25mcg

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12
Q

what is the usual replacement dose of levothyroxine approxiamately?

A

0.5mcg/kg/d for elderly; 1.7 mcg/kg/d <50

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13
Q

What SEs are common with thyroid replacement?

A

should be none; counsel patients on sx of hyperthyroidism (increased HR tachycardia weight loss irritability)

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14
Q

What is the IV:PO ratio for levothyroxine?

A

1:2

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15
Q

What should be seperated from levothyroxine by 4 hours?

A

aluminum calcium cholestyrimine iron mg multivitamines (ADEK) folate orlistat sevelamer sodium ALL decrease absorption of levopolystyrine sucralfate

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16
Q

How long before levothyroxine starts working?

A

may see reduction in sx in 1to 2 weeks but not the full effect for 1 to 2 months (similar to antidepressants!)

17
Q

What drugs can cause hyperthyroidism?

A

iodine amiodarone interferons

18
Q

What are the two thionamides and what is their MOA?

A

propylthiouracil and methimazole; inhibit synthesis by blocking oxidation of iodine and PTU also inhibits peripheral conversion

19
Q

What is a BB with PTU?

A

severe liver injury and acute liver failure

20
Q

What are common SEs with PTU and methimazole?

A

GI upset HA rash itching fever hepatitis agranulocytosis

21
Q

In pregnancy which thionamides are preferred and when?

A

PTU in the 1st trimester and methimazole in the 2nd and 3rd

22
Q

What are the iodides products used to treat hyperthyroidism?

A

potassium iodide and iodide solution (Lugol’s) saturated solution of of potassium iodide (SSKI)

23
Q

What is thyroid storm and how is it treated?

A

decompisated hyperthyroidism; 5 things PTU given 1 hr before iodide PLUS SSKI or Lugols PLUS beta blockade (ex. propranolol); PLUS corticosteroid PLUS aggressive cooling WITH APAP and cooling blankets

24
Q

what are the contraindications for levothyroxine

A

Acute MI, thyrotoxicosis, uncontrolled adrenal insufficency

25
Q

What is the starting dose of desicated thyroid is an elderly pt w/ cardiac issues

A

15mg

26
Q

What agents decrease the absoprtion of levothyrosine

A

cholestyramine, Ca, Mg, Al, Fe, sucralfate, orlistat, chromium; levo should be taken 2hours before or 4 hours after these

27
Q

What agents decrease thyroid levels

A

estrogens & CYP inducers

28
Q

What agents reduce the conversion of T4 to T3?

A

BBs, amiodarone, steroids, PTU