Treatment of Thyroid dz Flashcards

1
Q

function of the thyroid

A

metabolic rate. Iodine uptake, thyroglobulin production. Hormone secretion T3 and T4

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2
Q

thyroid physiology

A

iodide transport into thyroid–>thyroid peroxidase oxidized iodide–>Binds to iodinated tyrosine in thyroglobulin–>Combone to form T3 T4—>further breakdown of T4 to T3

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3
Q

What is feedback loop for thyroid homeostasis?

A

Hypothalmic pituitary thyroid axis - negative feedback.

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4
Q

Drugs that increase TBG will mean?

A

Less free thyroid hormone (more binding will occur)

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5
Q

Increase serum TBG is the result of?

A

Estrogen, Tamoxifen, Heroin, Methadone, Mitotane, Fluorouracil

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6
Q

Decreased serum TBG is result of?

A

Androgens, Anabolic steroids, Slow release nicotinic acid, Glucocorticoids

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7
Q

diagnostic criteria for hyperthyroidism

A

Decreased TSH, Increased T3 and T4 (free and total)

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8
Q

TX for hyperthyroidism

A

ATD, RAI, Surgery, Smptomatic (Beta-blockers)

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9
Q

What is first line tx for hyperthyroidism?

A

Thioamides, Methimazole for most PTU for thyroid storm of 1st trimester moms.

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10
Q

MOA Thioamides

A

inhibits thyroid synth. Depletes stored hormon.
PTU-inhibits T4 to T3 conversion within hours. For pregnant pt’s -PTU preferred in 1st trimester. When breastfeeding Methimazole is preferred PTU can cause hepatotoxicity

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11
Q

Dosing of Thioamide (methimazole)

A
Methimazole: 
Initial
Mild: 15mg/day
Moderate: 30-40 mg/day
Severe: 60 mg/day
Continue 4-8 weeks until euthyroid 

Maintenance: 5-15mg/day

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12
Q

Dosing of PTU

A

Intial :
100-150mg q 6-8h
Continue 4-8wks until euthyroid

Maintenance:
50-150mg/day

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13
Q

when should you test TSH after starting a pt on thioamides?

A

Don’t test for first 2-3 mos. Not accurate

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14
Q

When should you test for T4 after starting pt on thioamides?

A

4-8 weeks after starting. After remission (1year normal values) can follow up every 6-12mos.

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15
Q

P’Kinetics of Thioamides

A

A: well absorbed from GI tract
D: Concentrates in Thyroid, 80% protein bound PTU
M: Liver
E: Renal
H: methimazole 5-13 hours, PTU 1-2 hours

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16
Q

ADE thioamides

A
GI upset
Arthralgia
Rash, urticaria, pruritis
Serious: 
Agranulocytosis, Hepatotoxicity
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17
Q

Caution with PTU

A

Watch for: Hepatotixicity, jaundice, joint pain, and pain etc. Check LFT’s, WBC’s Free T4

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18
Q

How soon should TSH be tested a after patient achieves remission?

A

2-3 mos.

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19
Q

Iodides MOA

A

Inhibits thyroid hormone release
Decrease thyroid hormone synthesis
Decrease thyroid gland vascularity
initial effect within 24 hours max 10-15 days of continuing therapy.

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20
Q

Uses for iodides in thyrotoxicosis

A

Reduced vascularity prior to thyroid surgery
prepare patients with Graves Dz for surgery
Decrease thyroid iodine accumulation in thyrotoxic crisis
prevent thyroid uptake of RI

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21
Q

ADE for Iodide

A

Rash, GI upset, Parasthesia, Immune hypersensitivity rx, Salivary gland swelling.
Iodism-burning in mouth or throat, metallic taste, sore teeth and gums, cold symptoms

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22
Q

MOA Lithium

A

Blocks T4 and T3 from release of gland-not recommended in ATA/AACA guidelines. d/t adverse effects

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23
Q

What do Beta Blockers do for pt’s with hyperthyroid?

A

Symptomatic treatment of palpitations, tachycardia, tremor, heat intolerance. Tx/ for thyrotoxicosis, thyroid storm, mono therapy for thyroditis

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24
Q

MOA beta blockers

A

Blocks beta adrenergic receptors to stop thyrotoxicosis

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25
Q

DI beta blockers

A

Anty-hyperglycemic agents, Diuretics, Anticholinergics, Ca channel blocers

26
Q

ADE Beta blockers

A

Fluid retention, bradycardia, hypotension, fatigue, Caution with restrictive airway dz

27
Q

RAI MOA

A

Sodium iodide 131. Taken into thyroid by TSH-R, incorporated into thyroid hormone and stored in the colloid, Emits beta particles and irreversible damages thyrocytes.

28
Q

Monitoring for RAI

A

T3 and T4 2-4 weeks post tx.
hypothyroidism will occur for 4-8 weeks post tx.
may take 6 mos. to see full tx response

29
Q

Which beta blockers are still available IV?

A

Metoprolol, Esmolol, Labetolol

30
Q

What medication can induce thyroiditis?

A

Amiodarone.

31
Q

Devine Type 1 amiodarone induced thyroiditis and tx.

A

Iodine induced
Usually underlying thyroid disease
Tx: Thioamides

32
Q

Define Type 2 amiodarone induced thyroiditis and tx.

A

Inflammatory
Leakage of thyroid hormone into cirulation
tx: glucocorticoids

33
Q

How do you tell the difference between Type 1 and Type 2 amiodarone induced thyroiditis?

A

Typically tx for both because it is difficult to tell the difference between type 1 and 2.

34
Q

What is the most common type of hypothyroid Primary or secondary?

A

Primary is MC. Hashimoto’s mc of primary

35
Q

What causes secondary hypothyroidism?

A

Ptiuitary dz, hypothalmic dz.

36
Q

What drugs can induce hypothyroidism?

A

Amiodarone, Suntinib, Lithium, Interferon, Thalidomide, Bexarotene, Ethionamide, Rifampicin, Antithyroid meds PTU and methimazole

37
Q

When do you tx for subclin hypothyroidism?

A

when TSH > 10 mlU/L

38
Q

define Myxedema

A

Severe hypothyroidism. Assoc with CAD. Can result in coma-medical emergency, requires ICU, Intubation, IV levothyroxine loading dose

39
Q

Lab findings for Hypothyroidism

A

TSH up, FT4 down

40
Q

When to start meds for hypothyroidism

A

TSH >10mlU/L

41
Q

What is first line med for hypothyroidism?

A

Synthetic L-thyroxine

42
Q

P’Kinetics of Levothyroxine

A

A: 40-80% bioavailable, increases with fasting, decreases with fiber
D: 99% protein bound TBG, TBPA
M: 80% hepatic, renal, enterohepatic recirculation (IV meds will bypass this)
E: Renal 80%, Fecal 20%
H: 6-7 days

43
Q

What factors can decrease absorption of levothyroxine?

A

Cholestyramine, Ca Carbonate, Sucralfate, Aluminum hydroxide, Ferrous Sulfate, Soybean, Dietary fiber, FOOD

44
Q

What factors can increase elimination of levothyroxine?

A

Carbamazepine, phenytoin, Rifampin, sertraline, quetiapine, phenobarbital

45
Q

Dosing for Levothyroxine

A

Full replacement dose 1.6mcg/kg/day (need to titrate up)

46
Q

Target TSH for tx with levothyroxine

A

0.5-4 mlU/L avoid TSH <0.1mlU/L especially in older patients and post-menopausal women

47
Q

Monitoring frequency for L-thyroxine

A

4-6 weeks after initiation of therapy

Once normal should measure TSH and FT4 once every 6-12 most.

48
Q

Administration of L-thyroxine

A

Oral 60min prior to meal
Or - 3 hours post meal at bedtime
Or- 30 min before meal
Or with breakfast as long as b-fast is same thing and time every day.

49
Q

Liothyronine definition

A

Chemically pure synthetic T3

50
Q

disadvantages of Liothyronine

A

Higher incidence of cardiac effect
higher cost
difficult to monitor with conventional tests
non considered 1st line (not recommended by AACA)

51
Q

Liotrox define

A

T4;T3, Rasio is 4:1, mimics natural hormone secretion.

52
Q

Disadvantages of liotrox

A

high cost
Lack of therapeutic rationale
Non consistent strong evidence

53
Q

What is appropriate levothyroxine dose for a 75 kg male?

A

125 mug daily . (1.6X75)=120

54
Q

ADE Levothyroxine

A
Allergic reaction (uncommon)
uncommon at appropriate dosages but overtx may produce increased hyperthyroid sx.
55
Q

Natural thyroid hormone definition

A

Desiccated thyroid, compounded from hog, beef, sheep, armor thyroid most common type.

56
Q

How much should levothyroxine dose be increased for pregnant women?

A

It should be increased 30%

57
Q

DI thyroid replacement tx. and Amiodarone and what do you do about it?

A

increases or decreases thyroid levels, Monitor TSH and FT4 levels at baseline every 6 mos

58
Q

DI thyroid replacement tx and digoxin and what do you do about it?

A

Increase digoxin levels. Decrease dose of thyroid med

59
Q

DI thyroid replacement tx and Warfarn and what do you do about it?

A

increase or decrease anticoag. Monitor INR frequently with changes of dose for either med.

60
Q

DI thyroid replacement tx and Insulin and what do you do about it?

A

Increased risk of hyperglycemia. Increase insulin dose and monitor blood sugars.

61
Q

What factors can decrease serum levels of Levothyroxine?

A

Advancing age,
Extreme obesity
GI disorders