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Summer Pharm Exam 1 > Thyroid > Flashcards

Thyroid Flashcards

1
Q

What is your thyroid test of choice

A

TSH! thyroid stimulating hormone, released form anterior pituitary

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2
Q

What is graves disease

A

AI d/o (Abs stimulate thyroid to make hormones) resulting in hyperthyroidism in early phase
can progress to hypothyroid later if there is gland destruction

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3
Q

What is a thyroid storm

A

severe thyrotoxicosis (excess thyroid hormone)

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4
Q

What is goiter

A

enlargement of thyroid gland

can occur in hyper or hypothyroidism

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5
Q

What is the role of the thyroid

A

Normal growth and development in kids

metabolic stability in adults

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6
Q

The first way the thyroid is regulated is

A

TSH secreted by anterior pituitary

Negative feedback on anterior pituitary is from circulating free thyroid hormone, and release of TRH from hypothalamus

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7
Q

Extrathyroidal deiodination of T4 to T3 is regulated by

A 
nutrition 
nonthyroid hormones 
ambient temps 
drugs 
illness
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8
Q

How id thyroid hormone synthesized

A

Iodide transported from plasma to apical membrane of the cell, and coupled to TG
Hormone stored as colloid moves back towards basal membrane where T4 is secreted

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9
Q

Where are the thyroid hormones formed and secreted

A

T4: secreted from thyroid ONLY
T3: 80% made from breakdown of T4 (5-monodeiodinase in extrathyroidal peripheral tissues converts T4 to T3)

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10
Q

How are T4 and T3 transported in the bloodstream

A

They are bound to 3 proteins; thyroxine binding globulin, transthyretin, and albumin
99.6% are bound

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11
Q

What are UNbound thyroid hormones able to do

A 
diffuse into cell 
elicit biologic effect 
regulate TSH (thyrotropin)
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12
Q

Where are thyroid hormone receptors found

A

in hormone responsive tissues;
pituitary, liver, kidney, heart, skeletal muscle, lung, intestine
(T3 has more affinity for these receptors than T4)

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13
Q

How does the body preserve homeostasis

A

by altering number of thyroid receptors

ex: starvation lowers T3 hormone and receptors

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14
Q

What thyroid hormone gives the negative feedback

A

T3!
When there is too much T3, it gives negative feedback to the thyroid to stop releasing TSH, and hypothalamus to stop releasing TRH

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15
Q

What are S/Sx of thyrotoxicosis

A 
warm moist skin 
sweating 
tachycardia 
dyspnea 
tremor, weak
weight loss
menstrual irregularity 
graves: exophthalmos
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16
Q

What are S/Sx of hypothyroid

A 
pale, cool, puffy skin 
always cold 
bradycardia 
HTN 
PE
reduced appetite, weight gain
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17
Q

Many hypothyroid patients on treatment dont see weight loss, so what do they do

A

double the thyroid med dose causing heart and bone problems

advise patient that taking thyroid medication will NOT correct their weight gain

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18
Q

What is Hashimotos

A

AI destruction of thyroid gland

early dz has goiter

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19
Q

What can cause hypothyroidism

A 
Hashimotos 
drug induced 
dyshormonegensis 
radiation 
congenital (cretinism) 
Seconadary (TSH deficiency)
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20
Q

What will primary hypothyroid labs show

A 
High TSH (>4.5) 
Decreased free T4
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21
Q

What will secondary hypothyroid labs show

A

TSH within or below normal limits
Free/total T4 and T3 are low
antithyroid peroxidase Abs and anti-TG abs elevated if AI

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22
Q

What will subclinical hypothyroid labs show

A 
High TSH (>4.5) 
Normal free T4
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23
Q

What lab do you not need to diagnose hypothyroidism

A

T3, free or total

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24
Q

When should subclinical hypothyroid be treated

A

Only if TSH >10, or if pt has iron deficiency anemia
-Controversial because some say there is no improvement with treatment, others say Tx can help improve lipid profiles and LV function

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25
Q

How should you treat and monitor hypothyroidism in pregnant women

A

Adjust replacement therapy (increase dose from 25-50%)
First trimester: monitor TSH monthly- goal is 2-2.5
second trimester: goal TSH <3
third trimester: goal TSH <3.5
postpartum: check TSH at 6 weeks

26
Q

What labs shouldyou order for different thyroid disorders

A

Screening: TSH and fre T4
Hypo: TSH, anti-TG abs, anti-TPO abs
Hyper: TSH, free T4, I uptake scan, anti-TPO and anti-TG abs
Thyroid nodule: FNA, I uptake scan, Tc scan, US

27
Q

Increased thyroid binding globulin will show what lab values

A

elevated total T4 and T3

*free T4 and TSH will not be affected

28
Q

What drugs can cause low serum T4 or T3

A

Naproxen
Octreotide (somatostatin analog)
Phenobarbitol
Phenytoin

29
Q

What drugs increase TSH (hypothyroid)

A 
Phenytoin 
Amiodarone 
Dopamine antagonist 
salicylates 
naproxen 
estrogen or androgen excess
30
Q

What disorders can alter lab results

A 
severe illness 
pregnancy 
chronic protein malntr
hepatic failure 
nephrotic syndrome
31
Q

What is first line for treating hypothyroidism

A 
Levothyroxine; synthetic T4 that is relatively inexpensive, chemically stable, with uniform potency 
dose daily (half life 7 days) 
WHITE TABLET is 50 mcg; relative dose is 100mcg so usually Rx 2 white pills
32
Q

If you change a dose of levothyroxine, how long do you wait to recheck lab values

A

4-5 weeks; half life is 7 days, wait 4-5 half lives

apps. 6 weeks

33
Q

How are T4 and TSH related

A

non-linearly

small changes in T4 can have enormous changes in TSH

34
Q

How do you take levothyroxine

A

with water, on an empty stomach, 1 hr before breakfast
food impairs it’s absorption (as well as mucosal diseases- sprue, diabetic diarrhea, ileal bypass surgery)
-give meds that interact with levothyroxine 4 hours after T4 dose

35
Q

What can impair absorption of levothyroxine in the GI tract

A

*cholestyramine (bile acid resin)
*calcium carbonate
sucralfate
aluminum hydroxide
*ferrous sulfate
dietary fiber
espresso
*histamine blockers, PPI

36
Q

What drugs increase T4 clearance

A

Rifampin
carbamazepine
phenytoin
*selenium deficiency and amiodarone block conversion of T4 to T3

37
Q

What do some people say happens when they take T3 (Cytomel)

A

they get a burst of energy

but; some formulations deliver too much T3

38
Q

What is Armour thyroid

A

Dessicated pork thyroid gland

39
Q

Most patients require this dose once they reach steady state

A

1.7 mcg/kg/day levothyroxine

dose is based on ideal body weight, not actual body weight

40
Q

How do you dose young patients w/ long standing dz or pt <45 w/o cardiac disease

A

Start on Levothyroxine 50mcg daily, increase to 100mcg daily after 1 month

41
Q

Recommended dosing for older patients with CAD on levothyroxine

A

Start 25 mcg per day

titrate up 25mcg at monthly intervals

42
Q

Why do pregnant women need a higher thyroxine dose

A

increased degredation by placental deiodinase
increased T4 pool size
transfer of T4 to fetus
also may need to increase dose in post-menopausal women

43
Q

What are some disease drug interactions in hypothyroidism

A

High serum digoxin values 2/2 decreased drug distribution

Decreased sensitivity to warfarin (low K clotting factors)-

44
Q

Excess thyroid hormone can lead to

A

HF
angina pectoris
MI
-hyperremodeling of cortical and trabecular bone= reduced bone density and increased risk of Fx

45
Q

What is the least allergenic levothyroxine tables

A 
50mcg tab (WHITE) 
no dye, few excipients- try this in pts suspected of thyroid hormone allergy
46
Q

What are symptoms of hyperparathyroid

A 
nervous
anxiety
emotionally labile 
palpitations 
menstrual disturbance
heat intolerance 
**Weight loss with increased appetite**
47
Q

Hyperthyroid PE findings include

A

warm, smooth moist skin
fine hair
graves: exopthalmos and pretibial myxedema

48
Q

How do you treat hyperthyroidism

A

anti-thyroid drugs (first line in kids, teen, and pregnant)
RAI
surgery

49
Q

Advantages and disadvantages of anti-thyroid drugs are

A

Ad: non-invasive, low cost, low risk permanent hypothyroid
Dis: low cure rate, drug interactions, hard to comply

50
Q

What are the Thiourea (antithyroid) drugs

A

Propothyrouracil and Methimazole
Preferential substrates to iodinating peroxidase= inhibited coupling of mono/diiodityrosine so T3 and T4 do not form
Take 4-8 weeks to see normalization of thyroid hormone

51
Q

What are the pharmacokinetics behind thiourea drugs

A

mostly absorbed in GI tract (peak concentration 1hr s/p eating)
concentrated in thyroid gland
excreted in urine

52
Q

How are Thiourea drugs doses

A

PTU: 300-600 mg daily, TID/QID
MMI: 30-60mg daily, BID/TID
-can also give them as one dose
change dose on a monthly basis (allow T4 to reach steady state)

53
Q

ADE of thiourea drugs are

A 
Pruritic maculopapular rash 
benign transient leukopenia 
agranulocytosis 
arthralgias 
Lupus like syndrome 
*hepatotoxicity
54
Q

When is the only time PTU is considered a first line drug

A

First trimester pregnancy, at lowest possible dose to maintain maternal T4 in normal-high range
WHY? because in first trimester, embryopathy associated w/ MMI is worse than hepatotoxicity associates with PTU

55
Q

When on thiourea drugs while pregnant, your goal is to

A

prevent fetal goiter and suppress fetal thyroid function

*PTU <200= not likely to get fetal goiter

56
Q

What is the MOA of Iodides

A

block thyroid hormone release
inhibit thyroid hormone synthesis (interfere w/ intrathyroidal iodide utilization)
decrease size and vascularity of thyroid gland
*BUT- thyroid hormone synthesis still continues, so you get a thyroid full of stored hormones that cant release them

57
Q

When should you give potassium iodide

A

7-14 days preoperatively

*If giving w/ RAI, give SSKI 3-7 days after Tx so radioactive iodide can concentrate in the thyroid

58
Q

ADE of Iodides are

A

salivary gland swelling

iodism (metallic taste, burning mouth/throat, sore teeth and gums, gynecomastia)

59
Q

Radioactive iodine is the best Tx for

A

toxic nodules
toxic multinodular goiter
*good cure rate of hyperthyroid

60
Q

Disadvantages of RAI are

A

permanent hypothyroidism

Cant get pregnant for 6-12 months; can NOT breast feed

61
Q

When s surgery used in hyperthyroidism

A

If pregnant and have major ADE from anti-thyroid drugs

if you have a coexisting susp nodule

Summer Pharm Exam 1 (8 decks)

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