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Endocrinology > thyroid > Flashcards

thyroid Flashcards

1
Q

only _____ thyroid hormone has biological effects

A

unbound

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2
Q

t4 source vs t3 source

A

T4 only source is thyroid gland
T3 <20% comes from thyroid gland. most is produced by breakdown of T4 by deiodinase enzyme

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3
Q

binding affinity T3 vs T4

A

T3 has a 10-15x higher binding affinity than T4

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4
Q

t/f: all thyrotoxicosis is hyperthyroidism

A

false

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5
Q

the symptoms of thyrotoxicosis can be described as

A

speeding up and heating up
ex hyperactive, sweating, palpitations, weight loss w/ inc appetite, diarrhea, etc

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6
Q

diagnostics of thyrotoxicosis

A

decreased TSH (due to negative feedback)
increased T3, T4
RAIU
TSAbs if grave’s disease

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7
Q

what are the most common causes of thyrotoxicosis with increased RAIU

A

Grave’s disease
toxic adenoma
multinodular goiter

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8
Q

which is the most common cause of hyperthyroidism

A

Grave’s

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9
Q

describe actions of grave’s?

A

autoimmune: actions of thyroid-stimulating antibodies (TSAbs) against thyrotropin receptor
thyroid enlarged 2-3x normal
disproportionate increase in T3 relative to T4

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10
Q

description of toxic adenoma?

A

“hot nodule”
autonomous thyroid nodule, benign tumor producing thyroid hormone

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11
Q

description of multinodular goiter?

A

autonomous follicles

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12
Q

most common causes of thyrotoxicosis with suppressed RAIU

A

subacute thyroiditis
painless thyroiditis
exogenous thyroid hormone
meds containing iodine

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13
Q

describe subacute thyroiditis/treatment?

A

systemic symptoms like flu: fever, malaise, myalgia
self limiting: ANTITHYROID DRUGS ARE NOT INDICATED
treatment is symptom management: beta blockers, NSAIDS, prednisone

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14
Q

describe painless thyroiditis/treatment?

A

painless/silent– can happen postpartum. self-limiting: antithyroid drugs are not indicated. give propranolol or metoprolol

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15
Q

what can cause ingestion of exogenous thyroid hormone

A

overtreatment, pharmacy errors, accidental– ground beef contaminated

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16
Q

what medications contain iodine that can induce thyrotoxicosis

A

amiodarone

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17
Q

withhold ____ for 24-48 hours prior to laboratory testing

A

biotin

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18
Q

antithyroid medications

A

methimazole first line
propylthiouracil

19
Q

when to consider surgery for thyrotoxicosis

A

large thyroid gland >80g
severe ophthalmopathy
lack of remission

20
Q

when is radioactive iodine the choice therapy for thyrotoxicosis

A

toxic nodules & multinodular goiter

21
Q

disadvantages for radioactive iodine

A

permanent hypothyroidism
worsening ophthalmopathy: avoid in eye disease
contraindicated in pregnancy and breastfeeding, defer pregnancy x 6 months

22
Q

what is the limitation to methimazole

A

possible teratogen, avoid 1st trimester pregnancy

23
Q

surgery downside for thyrotoxicosis

A

leads to permanent hypothyroidism

24
Q

what are the limitations for propylthiouracil

A

hepatotoxicity
limited to: 1st trimester pregnancy, thyroid storm, patients with adverse effects to methimazole

25
Q

thyroid storm

A

life threatening medical emergency

26
Q

primary hypothyroidism: causes

A

hashimoto’s, iatrogenic

27
Q

what is central hypothyroidism

A

dysfunction of pituitary or hypothalamus

28
Q

what is hashimoto’s

A

autoimmune; antithyroid peroxidase antibodies, presents as goiter/ hypothyroidism

29
Q

what causes iatrogenic hypothyroidism

A

destructive amounts of radiation, surgery

30
Q

pituitary disease of central hypothyroidism culprit is __

A

TSH

31
Q

hypothalamic disease of central hypothyroidism culprit is ___

A

TRH deficiency

32
Q

hypothyroidism presentation can be described as

A

slowing and cooling
children: delays growth, development
dry skin, cold intolerance, weight gain, constipation, weakness

33
Q

diagnosis of hypothyroidism

A

increased TSH for primary
inappropriately normal TSH for secondary
autoantibodies in hashimoto’s

33
Q

treatment of hypothyroidism

A

levothyroxine

34
Q

liothyroxine

A

higher incidence of cardiac adverse events

34
Q

desiccated thyroid

A

antigenic in allergic/sensitive patients

35
Q

levothyroxine at excessive doses can cause

A

heart failure, angina, MI, decreased bone density

36
Q

starting dose for levothyroxine

A

25 mcg for elderly with known cardiac disease
50 mcg for most

37
Q

titrating levothyroxine

A

25 mcg increments monthly
average maintenance dose is 125 mcg

38
Q

levothyroxine with food

A

food impairs absorption

39
Q

TSH normal range

A

0.5 to 4.5

40
Q

levothyroxine drug interactions

A

H2RAs, PPIs, rifampin, carbamazepine, phenytoin

41
Q

myxedema coma

A

decompensated hypothyroidism: need IV levothyroxine and IV hydrocortisone

42
Q

pregnancy with hypothyroidism

A

increase levothyroxine dose 20-30%: 2 additional tablets a week

Endocrinology (10 decks)

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