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RxPrep > Thyroid disorders > Flashcards

Thyroid disorders Flashcards

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?

A

Levothyroxine (T4)

25
Q

Levothyroxine (T4)

A

SYNTHROID
LEVOXYL
UNITHROID

26
Q

What is a full replacement dose of levothyroxine?

A

1.6 mcg/kg/day (of IBW)

27
Q

Thyroid, Desiccated USP (T3 and T4)

A

Armour Thyroid

28
Q

What is the starting dose of levothyroxine in those with known CAD?

A

12.5-25 mcg/day

29
Q

Liothyronine (T3)

A

Cytomel

30
Q

What drugs need to be separated from levothyroxine by 4 hours so they don’t reduce absorption of T4?

A
  1. antacids
  2. Fe, Ca, Al, Mg
  3. multivitamins (ADEK, folate)
  4. cholestyramine
  5. orlistat (Xenical, Alli)
  6. sevelamer
  7. sucralfate
31
Q

What drugs need to be separated from levothyroxine by 3 hours so they don’t reduce absorption of T4?

A

sodium polystyrene sulfonate (veltassa)

32
Q

What drugs need to be separated from levothyroxine by 2 hours so they don’t reduce absorption of T4?

A

Lanthanum

33
Q

What drugs decrease thyroid hormone levels?

A
  1. estrogen
  2. SSRIs
  3. hepatic inducers
34
Q

What drugs decrease effectiveness of T4?

A
  1. beta-blockers
  2. amiodarone
  3. PTU propylthiouracil
35
Q

How does thyroid hormone replacement affect warfarin?

A

increase INR

36
Q

What colors are levothyroxine tablets?

A

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
Q

What are key counseling point with levothyroxine?

A
  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
Q

What is the most common cause of hyperthyroidism?

A

Grave’s disease- antibodies stimulate thyroid gland

39
Q

What medications can cause hyperthyroidism?

A

1.iodine
2. amiodarone
3. interferons
4. radiographic contrast media

40
Q

What are treatments for hyperthyroidism?

A
  1. PTU/methimazole
  2. radioactive iodine (destroy thyroid)
  3. surgery
41
Q

What medication can be used to control tremor, tachycardia, and palpitations associated with hyperthyroidism?

A

beta-blocker

42
Q

What are s/sx of hyperthyroidism?

A
  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
Q

How long should treatment for hyperthyroidism last?

A

1-3 months at high doses to control symptoms, then reduce dose to prevent hypothyroidism

44
Q

What are boxed warnings with PTU?

A
  1. severe liver injury and acute liver failure
  2. PTU preferred in 1st trimester of pregnancy
45
Q

What are warnings with PTU and methimazole?

A
  1. HEPATOTOXICITY
  2. bone marrow suppression (AGRANULOCYTOSIS)
  3. DRUG-INDUCED LUPUS ERYTHEMATOUS
46
Q

What are SEs with PTU and methimazole?

A
  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
Q

What should be monitored with PTU and methimazole?

A
  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
Q

What are counseling points with PTU and methimazole?

A

take with food to reduce GI upset

49
Q

What is the DOC for hyperthyroidism?

A

methimazole

50
Q

What is the DOC for thyroid storm?

A

PTU

51
Q

What agent is preferred is the 2nd/3rd trimester?

A

methimazole, decreased liver toxicity

52
Q

What is the MOA of thionamides?

A

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
Q

What agents are thionamides?

A
  1. methimazole
  2. Propylthiouracil (PTU)
54
Q

What is the MOA of iodides?

A

temporarily inhibit secretion of thyroid hormones; reduces T4 and T3 for a few weeks

55
Q

What agent blocks the accumulation of radioactive iodine to prevent thyroid cancer and should be used after radiation exposure?

A

potassium iodide

56
Q

What are s/sx of thyroid storm?

A
  1. fever >103
  2. tachycardia
  3. tachypnea
  4. dehydration
  5. profuse sweating
  6. agitation
  7. delirium
  8. psychosis
  9. coma
57
Q

What is the treatment algorithm for thyroid storm?

A
  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
Q

How much should levothyroxine dose be increased during pregnancy?

A

30-50%

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