Thyroid disease

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What is the minimum amount of iodine required per day?

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1

What is the minimum amount of iodine required per day?

150 micograms/day

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2

Where is excess iodine excreted?

urine and stool

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3

What is the Wolff-Chaikoff effect?

high iodine levels can inhibit further iodine uptake into the thyroid → transient hypothyroid symptoms

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4

Where is T4 converted to T3?

in the periphery

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5

Which form of iodine makes up the bulk of iodine in the body?

T4 - 90%

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6

What form of iodine is considered active thyroid hormone?

T3 - 9%

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7

What form of iodine is biologically inactive?

rT3 - 1%

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8

What is the T 1/2 of T4?

7 days

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9

What is the T 1/2 of T3?

1 day

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10

Which form of iodine has a greater oral bioavalabity?

T3 - 95% oral absorption

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11

How much T4 is naturally made by the body per day?

75 mcg

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12

How much T3 is naturally made by the body per day?

25 mcg

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13

What is the major function of TH?

  • regulate growth & development in fetal & childhood

  • regulates metabolism

  • regulates energy expenditure

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14

What is the condition called with iodine deficiency during fetal development?

Cretinism- PREVENTABLE

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15

What is iodine deficiency in adults called?

myxedema

can cause coma

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16

What is hyperthyroidism?

Thyroid hormone in excess

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17

What is hypothyroidism?

thyroid hormone deficiency

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18

What is the TSH level with hypothyroidism?

High TSH → continually saying need more TH

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19

What is the TSH level in hyperthyroidism?

Low TSH

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20

What is Hashimoto’s disease?

Hypothyroidism

destructive autoantibodies attack thyroid gland

High TSH- signal need more TH

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21

What is Grave’s disease?

Hyperthyroidism

stimulatory autoantibody stimulate TH

low TSH level bc excess

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22

What are S/S of Grave’s disease?

skin: sweating, heat intolerance, thinning hair

ocular: upper eyelid retraction - BUG EYES

CV: elevated HR, Increased CO, arrhythmias, angina

Respiratory: Hypoventilation

GI: Increased peristaltic contractions

CNS: agitation, nervousness

Muscle: weakness, fatigue

Reproductive: Menstrual irregularities, infertility

Metabolic: Increased BMR, Increased drug metabolism

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23

What is a thyroid storm?

acute exacerbation of hyperthyroidism - LIFE THREATENING

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24

What are S/s of a thyroid storm?

palpitations

HF

hyperthermia

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25

What is the treatment for a thyroid storm?

CV symptoms- non-selective beta blockers (propranolol) if BB CI then use diltiazem

TH production: Potassium iodide or PTU

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26

What is the MOA of PTU in removing excess TH during a thyroid storm?

Sequester excess TH w/ bile acid (via cholestyramine) & fecal excretion or plasmapheresis

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27

What are the 4 classes of drugs used to treat hyperthyroidism?

  1. Thioamides

  2. Uptake inhibitors

  3. Radioactive Iodine

  4. Surgical resection

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28

What is the MOA of Thioamides?

Inhibit TPO (thyroid peroxidase enzyme)

inhibits T4 → T3 conversion in periphery

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29

When in practice are thioamides used?

Precursor to surgical removal of thyroid

can normalize TSH levels over time

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30

What are commmon AE of thioamides?

Goiter formation (continual thyroid stimulation via TSH)

Maculo-papular rash

arthralgia

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31

What are the rare but severe AE of thioamides?

agranulocytosis

hepatotoxicity

ANCA-+ vasculitis

pancreatitis

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32

How is hyperthyroidism controlled during pregnancy?

1st trimester- PTU is preferred bc higher plasma binding

2nd/3rd trimester- Methimazole preferred bc PTU can cause hepatotoxicity

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33

What is the MOA of Iodine uptake inhibitors (NIS)?

inhibit sodium-Iodine transporter

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34

When are iodine uptake inhibitors used?

hyperthyroidism via other drug interactions (ex amiodarone has iodine and can increase uptake)

Perchlorate rarely used bc risk of aplastic anemia

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35

What drug class does Perchlorate belong to?

Iodine Uptake inhibitors (NIS)

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36

When is radioactive iodine CI and why?

Pregnant and lactating women

risk of fetal thyroid destruction

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37

What is the only form of radioactive iodine?

Iodine 131

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38

What is the MOA of radioactive iodine?

concentrates in thyroid follicle & destroys cells

(epithelial swelling, necrosis, follicle disruption, edema, leukocyte infiltration)

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39

What is Iodide 127 and what is the MOA?

Lugol’s solution

non-radioactive

inhibits TH synthesis via Wolff-Chaikoff effect

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40

What other medications can inhibit peripheral T4 → T3?

Contrast media: Ipodate & Iohexol

Beta-blockers

Corticosteroids

Tyrosine Kinase Inhibitors

Lithium

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41

How do beta-blockers inhibit peripheral T4 → T3?

TH increases expression of B-AR

Hyperthyroidism resembles non-specific SNS stimulation

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42

How do corticosteroids inhibit peripheral T4 → T3?

inhibits 5’-deiodinase, decreases peripheral T3 production

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43

How do TKIs inhibit peripheral T4 → T3?

Sunitinb

causes hypothyroidism as expected ADR

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44

How does Lithium inhibit peripheral T3 → T4?

inhibits coupling of iodotyrosine to decrease T4 production & release

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45

What are 3 primary causes of hypothyroidism?

Hashimoto’s disease

Iatrogenic hypothyroidism

Less common: iodine deficiency, enzyme defects, thyroid hypoplasia, goitrogens

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46

When it is appropriate to treat hypotyroidism?

ELEVATED TSH

w/ normal or low free T4

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47

Why is T4 preferred for hypothyroidism supplementation?

Longer T 1/2 → allows for less dosing throughout day (7 days) → improves adherence

Predictable PK

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48

What is thyroid USP made of and what is its thyroid ratio?

desiccate pork thyroid gland

High T3:T4 (4:1)

inexpensive

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49

What is levothyroxine made of?

Synthetic T4

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50

What is Liothyronine made of and what is is T 1/2?

Synthetic T3

rapid onset

T 1/2 = 1.5 days

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51

What is Liotrix made of and what is the thyroid ratio?

Synthetic T4 & T3 (4:1)

risk of T2 thyrotoxicosis bc high ratio of T3 to T4

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52
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