RxPrep > Thyroid disorders > Flashcards

Thyroid disorders Flashcards

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1
Q

What is required for production of T3 and T4?

A

iodine

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2
Q

How is T3 made?

A

usually from the breakdown of T4; <20% directly produced by the thyroid gland

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3
Q

Does T3 or T4 have longer half-life?

A

T4

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4
Q

Is T3 or T4 more potent?

A

T3

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5
Q

What form of thyroid hormone is active and monitored in patients with thyroid disorders?

A

free T4

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6
Q

What can happen if hypothyroidism is left untreated or decompensates?

A

myxedema coma: life-threatening emergency characterized by poor circulation, hypothermia, hypometabolism

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7
Q

How is myxedema coma treated?

A

IV levothyroxine

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8
Q

What are s/sx of hypothyroidism?

A
  1. cold intolerance/sensitivity
  2. dry skin
  3. fatigue
  4. weakness/myalgias
  5. muscle cramps
  6. voice changes
  7. depression
  8. bradycardia
  9. constipation
  10. weight gain
  11. coarse hair/ hair loss
  12. menorrhagia (heavy period)
  13. memory/mental impairment
  14. goiter
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9
Q

What key drugs can cause hypothyroidism?

A

ITALC:
1. Interferons
2. Tyrosine kinase inhibitors (sunitinib)
3. Amiodarone
4. Lithium
5. Carbamazepine

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10
Q

What other drugs can cause hypothyroidism?

A
  1. oxcarbazepine
  2. eslicarbazepine
  3. phenytoin
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11
Q

What conditions can cause hypothyroidism?

A
  1. Hashimoto’s
  2. iodine deficiency
  3. pituitary failure
  4. congenital hypothyroidism
  5. surgical removal of thyroid gland
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12
Q

How is hypothyroidism diagnosed?

A

Low free T4 and high TSH

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13
Q

What is a normal free T4?

A

0.9-2.3 ng/dL

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14
Q

What is a normal TSH?

A

0.3-3 mIU/L

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15
Q

How often should TSH and symptoms be monitored?

A

every 4-6 weeks until levels are normal

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16
Q

What can happen if too much thyroid hormone replacement is given?

A
  1. A.fib
  2. fractures
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17
Q

What are boxed warnings for thyroid hormone replacements?

A
  1. ineffective and potentially toxic when used for obesity or weight reduction, especially in euthyroid patients
  2. high doses can cause serious, life-threatening effects particularly when used with anorectic drugs
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18
Q

What are contraindications for using thyroid replacement?

A

uncorrected adrenal insufficiency

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19
Q

What are warnings with thyroid replacement hormones?

A
  1. decrease the dose in CV disease (chronic hypothyroidism predisposes to CAD)
  2. decreases bone mineral density which can lead to osteoporosis
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20
Q

What are SEs with thyroid replacement hormones?

A
  1. hyperthyroid symptoms (dose too high)
  2. increased HR
  3. palpitations
  4. sweating
  5. weight loss
  6. arrhythmias
  7. irritability
  8. may need dose reduction with age (highly protein bound)
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21
Q

What are the monitoring parameters with thyroid replacement hormones?

A

TSH levels and clinical symptoms:
1. every 4-6 weeks until levels are normal
2. then every 4-6 months
3. annually

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22
Q

How should PO levothyroxine be taken?

A

with water at least 60 minutes before breakfast or at bedtime (at least 3 hours after the last meal)

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23
Q

What is the IV:PO ratio for levothyroxine?

A

0.75:1

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24
Q

What is the DOC for hypothyroidism?

Study These Flashcards
A

Levothyroxine (T4)

25
Levothyroxine (T4)
SYNTHROID LEVOXYL UNITHROID
26
What is a full replacement dose of levothyroxine?
1.6 mcg/kg/day (of IBW)
27
Thyroid, Desiccated USP (T3 and T4)
Armour Thyroid
28
What is the starting dose of levothyroxine in those with known CAD?
12.5-25 mcg/day
29
Liothyronine (T3)
Cytomel
30
What drugs need to be separated from levothyroxine by 4 hours so they don't reduce absorption of T4?
1. antacids 2. Fe, Ca, Al, Mg 3. multivitamins (ADEK, folate) 4. cholestyramine 5. orlistat (Xenical, Alli) 6. sevelamer 7. sucralfate
31
What drugs need to be separated from levothyroxine by 3 hours so they don't reduce absorption of T4?
sodium polystyrene sulfonate (veltassa)
32
What drugs need to be separated from levothyroxine by 2 hours so they don't reduce absorption of T4?
Lanthanum
33
What drugs decrease thyroid hormone levels?
1. estrogen 2. SSRIs 3. hepatic inducers
34
What drugs decrease effectiveness of T4?
1. beta-blockers 2. amiodarone 3. PTU propylthiouracil
35
How does thyroid hormone replacement affect warfarin?
increase INR
36
What colors are levothyroxine tablets?
Orangutans Will Vomit On You Right Before They Become Large Proud Giants Orange-25mcg White-50mcg Violet-75mcg Olive-88mcg Yellow 100mcg Rose-112 mcg Brown-125 mcg Turquoise-137mcg Blue- 150mcg Lilac-175 mcg Pink-200mcg Green-300mcg
37
What are key counseling point with levothyroxine?
1. take medication at same time on empty stomach with water (60min before breakfast or at bedtime) 2. drug interactions 3. if your pills looks different, speak to the pharmacist 4. requires annual bloodwork 5. may need dosage increase if pregnant or breastfeeding
38
What is the most common cause of hyperthyroidism?
Grave's disease- antibodies stimulate thyroid gland
39
What medications can cause hyperthyroidism?
1.iodine 2. amiodarone 3. interferons 4. radiographic contrast media
40
What are treatments for hyperthyroidism?
1. PTU/methimazole 2. radioactive iodine (destroy thyroid) 3. surgery
41
What medication can be used to control tremor, tachycardia, and palpitations associated with hyperthyroidism?
beta-blocker
42
What are s/sx of hyperthyroidism?
1. heat intolerance/sweating 2. weight loss 3. insomnia 4. tremor 5. agitation/nervousness/anxiety/ irritability 6. palpitations/tachycardia 7. fatigue/muscle weakness 8. exophthalmos, diplopia 9. frequent bowel movements/ diarrhea 10. light/absent menstrual period 11. goiter
43
How long should treatment for hyperthyroidism last?
1-3 months at high doses to control symptoms, then reduce dose to prevent hypothyroidism
44
What are boxed warnings with PTU?
1. severe liver injury and acute liver failure 2. PTU preferred in 1st trimester of pregnancy
45
What are warnings with PTU and methimazole?
1. HEPATOTOXICITY 2. bone marrow suppression (AGRANULOCYTOSIS) 3. DRUG-INDUCED LUPUS ERYTHEMATOUS
46
What are SEs with PTU and methimazole?
1. GI UPSET 2. headache 3. rash (exfoliative dermatitis, pruritus) 4. fever 5. constipation 6. loss of taste/ taste perversion 7. lymphadenopathy 8. bleeding
47
What should be monitored with PTU and methimazole?
1. T3 and FT4 every 4-6 weeks until euthyroid 2. TSH 3. CBC 4. LFTs 5. PT 6. signs of liver toxicity (abdominal pain, yellow skin/eyes, dark urine, nausea 7. infection
48
What are counseling points with PTU and methimazole?
take with food to reduce GI upset
49
What is the DOC for hyperthyroidism?
methimazole
50
What is the DOC for thyroid storm?
PTU
51
What agent is preferred is the 2nd/3rd trimester?
methimazole, decreased liver toxicity
52
What is the MOA of thionamides?
inhibit the synthesis of thyroid hormones by blocking the oxidation of iodine in the thyroid gland; PTU has an additional MOA inhibiting peripheral conversion of T4 to T3
53
What agents are thionamides?
1. methimazole 2. Propylthiouracil (PTU)
54
What is the MOA of iodides?
temporarily inhibit secretion of thyroid hormones; reduces T4 and T3 for a few weeks
55
What agent blocks the accumulation of radioactive iodine to prevent thyroid cancer and should be used after radiation exposure?
potassium iodide
56
What are s/sx of thyroid storm?
1. fever >103 2. tachycardia 3. tachypnea 4. dehydration 5. profuse sweating 6. agitation 7. delirium 8. psychosis 9. coma
57
What is the treatment algorithm for thyroid storm?
1. antithyroid drug (PTU preferred) 2. saturated solution of potassium iodide (SSKI) or Lugol's solution (KI) 3. Propranolol 4. Dexamethasone 5. acetaminophen/ cooling blanket give antithyroid drug ≥ 1hour before KI to block the synthesis of thyroid hormones
58
How much should levothyroxine dose be increased during pregnancy?
30-50%
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