08 Thyroid Disorders Quan Flashcards Preview

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Flashcards in 08 Thyroid Disorders Quan Deck (102):
1

What are the thyroid hormone functions?

Growth and development (long bone growth and neuronal maturation). Increase basal metabolic rate. Body temperature. Body homeostasis

2

What are the main steps in Thyroid Hormone Synthesis?

Hypothalamus releases thyrotropin-releasing hormone (TRH) to stimulate anterior pituitary. Pituitary releases thyroid stimulating hormone (TSH) to activate the thyroid gland. Thyroid gland produces T3/T4

3

For thyroid hormone regulation, what happens with Low T4/T3 levels?

Stimulates release of TRH from hypothalamus

4

For Thyroid Hormone Regulation, what happens with High T4/T3 levels?

Regulate negative feedback loop. Decrease production of TRH and TSH

5

What is Thyroxine?

T4

6

What is Triiodothyronine?

T3

7

What is the major circulating thyroid hormone?

T4, secreted by the thyroid

8

Which thyroid is more potent?

T3 is 4x more potent than T4

9

What is the half-life like for thyroid hormones?

T4 7 days. T3 1.5 days

10

What are the T3 concentrations like?

T3 has lower serum concentration than T4 (80% of T3 from T4 --> T3 conversion in the periphery)

11

What are the normal TSH concentrations?

0.5-5 milliinternational units/L

12

What are the TSH concentrations like in Hyperthyroidism?

Low

13

What are the TSH concentrations like in Hypothyroidism?

High

14

What are the normal Free T4 concentrations?

0.8-2.7 ng/dL

15

What are the Free T4 concentrations like in Hyperthyroidism?

High

16

What are the Free T4 concentrations like in Hypothyroidism?

Low

17

What are the normal Total T4 concentrations?

4.5-10.9 mcg/dL

18

What are the Total T4 concentrations like in Hyperthyroidism?

High

19

What are the Total T4 concentrations like in Hypothyroidism?

Low

20

What are the normal Total T3 concentrations?

60-181 ng/dL

21

What are the Total T3 concentrations like in Hyperthyroidism?

High or normal

22

What are the Total T3 concentrations like in Hypothyroidism?

Low or normal

23

What is the normal range for Thyroperoxidase (TPO)?

< 100 IU/mL

24

What are the normal Antithyroglobulin (ATgA) levels?

< 8%

25

What are the normal Thyroid Receptor Antibodies (TRAb) titers?

Titers Negative

26

What is the definition of Hyperthyroidism?

Heterogeneous group of disorders characterized by elevated levels of thyroid hormones in the blood

27

What is Graves Disease?

Most common cause of hyperthyroidism. Defect in the autoimmune system. Antibodies attack thyroid gland --> hypertrophy and overproduction of thyroid hormone. Antibodies also attack eye muscles and pertibial skin (causing bulging eyes)

28

How does Hashimoto's differ from Graves disease?

Hashimoto's disease is also an autoimmune disease, but causes atrophy instead of hypertrophy of the cells, causing hypothyroidism

29

What are some drugs that can cause Hyperthyroidism?

Amiodarone. Lithium. Iodines. Interleuin. Interferon-a

30

What are the lab findings like for Subclinical Hyperthyroidism?

Low TSH. Normal T3 and T4

31

What are the Subjective Signs of Hyperthyroidism?

Heat intolerance. Weight loss. Amenorrhea. Diarrhea. Photophobia. Palpitations. Nervousness, irritability, insomnia. Fatigue, weakness

32

What are the Objective Signs of Hyperthyroidism?

Goiter (bruits, thrills). Proximal muscle weakness on physical exam (d/t decrease in serum K). Tremor on physical exam. Proptosis (bulging eyes). Thinning of hair. Tachycardia. Wide pulse pressure. Palmar erythema. Pretibial myxedema

33

What is the preferred treatment for Hyperthyroidism?

Radioactive Iodine Therapy (I^131). For patients with cardiac disease, elderly, toxic multinodular goiter, failed thioamides, ophthalmopathy. Safe, but can lead to chronic hypothyroidism!!!

34

What are the contraindications for Radioactive Iodine Therapy?

Pregnancy. Breast feeding. Thyroid cancer

35

How can pre-treatment with thioamide help?

Decreases stored hormones. Decreases risk of worsening hyperthyroidism. Consider in elderly patients and patients with cardiac disease

36

When is surgery usually considered for hyperthyroidism?

Not commonly used, with exception of thyroid cancer. Reserved for patients non-responsive or intolerant to antithyroid medications. Patients with large thyroid goiters resistant to I^131. Pregnant patients

37

What are the complications of surgery for hyperthyroidism?

Hypoparathyroidism. Vocal cord paralysis

38

What are the pharmacological treatment choices for hyperthyroidism?

Thioamides. Iodide products

39

What are the Thioamides used for Hyperthyroidism?

Methimazole (Tapazole). Propylthiouracil (PTU)

40

What is the MOA of Thioamides?

Inhibits synthesis of thyroid hormones by inhibiting thyroid peroxidase-catalyzed reactions required for iodine oxidation. Inhibits the coupling of iodotyrosines. PTU inhibits peripheral conversion of T4 --> T3

41

How is Prophylthiouracil (PTU) dosed?

100mg PO QID. After 4-8 weeks, 50-150mg/day

42

How is Methimazole (Tapazole) dosed?

Initial 30-40mg PO QD. After 4-8 weeks, 5-14mg/day

43

What is the duration of Prophylthiouracil (PTU)?

7 hours

44

What is the duration of Methimazole (Tapazole)?

24 hours

45

What are the ADRs associated with Thioamides?

Rash, Arthalgias, Fever, Leukopenia. Serious: Agranulocytosis, Malaise, Gingivitis, Oropharyngeal infection, Granulocyte count < 250, Hepatotoxicity (PTU)

46

What needs to be monitored while on Thioamides?

TFTs Q6-8 weeks until euthyroid. TFTs Q6-12 months once patient is on a stable dose. TSH level may remain suppressed for the first several months after normalization of T4 and T3. CBC for first four months

47

What is the DOC for thyroid storm?

Prophylthiouracil (PTU)

48

What is the BBW associated with Prophylthiouracil (PTU)?

Hepatotoxicity

49

What is the onset time for Thioamides?

4-6 weeks

50

Which Thioamide is more potent?

Methimazole (Tapazole)

51

What DDI do you need to be careful about with Methimazole (Tapazole)?

May decrease the activity of Warfarin

52

As an adjunctive agent for hyperthyroidism, how does potassium iodide work?

Inhibits thyroid hormone synthesis. Blocks hormone release

53

When should you usually treat subclinical hyperthyroidism in people >65 years?

When TSH < 0.1

54

For people < 65 years, which comorbidities require you to treat subclinical hyperthyroidism when TSH < 0.1?

Heart disease. Osteoporosis. Hypoerthyroid symptoms. Consider menopause

55

What are the risk factors for Grave's Ophthalmopathy in Hyperthyroidism?

Elderly. Male. Smoker

56

What is treatment like for Graves Ophthalmopathy?

Treatment is directed at normalizing thyroid function. RAI or surgery preferred since it removes the antigen source. Corticosteroids adjunctive therapy following RAI (prednisone for 3-4 months)

57

What is Toxic Nodular Goiter?

More common than Graves' Disease in the elderly. Hyperthyroidism caused by multiple hyperfunctioning nodules. Different from Graves' in that it doesn't have autoantibodies involved or ophthalmopathy

58

What is the Treatment for Toxic Nodular Goiter?

Usually I^131, but surgery may be indicated if goiter is very large

59

What is the link between AF and Hyperthyroidism?

AF occurs in 10-20% of hyperthyroidism patients. Spontaneous recovery (must treat if no recovery in 1 year). Thromboembolism risk. Hypermetabolic state (if patient is on digoxin, increase dose. If patient is on warfarin, decrease dose)

60

What is the worst type of hyperthyroidism?

Thyroid Storm

61

What is Thyroid Storm?

Life-threatening clinical syndrome characterized by exaggerated signs and symptoms of hyperthyroidism, fever, and altered mental status. Precipitated by concurrent illness or injury, withdrawal of antithyroid medications or following I^131

62

What are the symptoms of Thyroid Storm?

Temperature > 103F. Tachycardia, arrhythmias, CHF, hypotension, tachypnea, dehydration, agitation, psychosis, delirium, coma, N/V/D, hepatic failure

63

What are the causes of Thyroid Storm?

Abrupt cessation of antithyroid hormone, acute illness, trauma, surgery, radioactive iodine therapy

64

What are T4 and T3 concentrations like in Hypothyroidism?

Low. T3 can be normal

65

What is Hypothyroidism?

Thyroid gland fails to secrete an adequate amount of thyroid hormone (most common thyroid disorder). Majority of causes of hypothyroidism are d/t primary thyroid gland failure. May also result from diminished stimulation by TSH

66

What is Primary Hypothyroidism?

Thyroid gland failure (thyroid can't produce amount of hormones pituitary calls for). Hashimoto's disease (chronic autoimmune thyroiditis). More common than secondary

67

What is Secondary Hypothyroidism?

Pituitary failure. Thyroid isn't being stimulated by pituitary to produce hormones

68

What is Tertiary Hypothyroidism?

Hypothalamic failure

69

What are some drugs that can induce Hypothyroidism?

Lithium. Amiodarone. Rifampin. Sulfonylureas. Iodine

70

What are the Subjective symptoms of Hypothyroidism?

Weakness, fatigue, sluggishness. Cold intolerance. Weight gain, constipation. Heavy menstrual periods. Dry skin, brittle hair. Slow speech. Muscles ache

71

What are the Objective symptoms of Hypothyroidism?

Goiter (primary hypothyroidism). Nonpalpable thyroid gland. Bradycardia. Edema. Cool, dry skin. Delayed relaxation of deep tendon reflexes. Depression

72

What is the general treatment outline for Hypothyroidism?

Thyroid hormone replacement options (synthetic (T4, T3 or combination) or natural (Variable potency and concentration ratios of T4 and T3))

73

What is the content of Levothyroxine?

Synthetic T4

74

What is the content of Liothyronine?

Synthetic T3

75

What is the content of Liotrix (Levothyroxine + Liothyronine)?

Synthetic T4:T3 in 4:1 ratio to mimic physiologic ratio

76

What are the general characteristics of Levothyroxine?

Body's own physiologic mechanism controls production of active hormone. Stable. Uniform potency. Lack of allergenic content

77

What is the general dosing of Levothyroxine in Adults?

1.6-1.7 mcg/kg/day

78

What changes to we need to make in pregnant patients on levothyroxine?

Increase dose by 20-30%

79

When dose adjusting Levothyroxine, how much can you adjust?

Not to exceed increments of 12.5 to 25mcg/day. Wait at least a month between each adjustment

80

What do you need to remember when changing PO Levothyroxine to IV?

Use 50% of oral dose

81

What is the time to steady state for Levothyroxine?

6-8 weeks

82

What needs to be monitored while on Levothyroxine?

TFTs (in particular T4, TSH)

83

When is Liothyronine (Cytomel) indicated?

Short-term replacement. Diagnostic agent. IV: treatment of myxedema coma

84

What is the main objective to using Liotrix (Thyrolar)?

Objective is to mimic natural hormone secretion (no clear therapeutic advantage)

85

What is a concern about using Desiccated Thyroid Hormone (Armour Thyroid)?

Variable potency. USP allowing for 15% variation in T4 and 10% variation in T3. Check labs every 4-6 weeks when changing manufacturers

86

What is the main kind of drug interaction with thyroid medications?

Chelation

87

What is the interaction between T4 and warfarin?

T4 enhances response to anticoagulant therapy

88

When should patients take their thyroid medications?

30 minutes before breakfast or other medications. Food can reduce absorption and fluctuate thyroid levels

89

How long will patients be on their thyroid medication?

Taken for life and will require laboratory blood tests every 6-12 months once you are on a stable dose

90

What side effects could indicate that the thyroid hormone dose is too high?

Fast HR. Diarrhea. Nervousness, tremor, insomnia. Heat intolerance, excessive sweating. Weight loss

91

What is Myxedema Coma?

Life-threatening state in which severe, usually long-standing hypothyroidism markedly worsens

92

What are the signs/symptoms of Myxedema Coma?

TSH, T4 and T3, electrolyte abnormalities. Hypothermia. Hemodynamic instability. Difficulty thinking. Lethargy to coma. Respiratory acidosis d/t decreased respiratory rate

93

What are the precipitating factors of Myxedema Coma?

Cold exposure, infection trauma. Anesthesia. Abrupt discontinuation of thyroid hormones after overuse of antithyroid medications

94

What is the treatment plan for Myxedema Coma?

Thyroid replacement (T4: IV bolus 300-600mcg, maintenance 50-100mcg T4 daily). Hydrocortisone (50mg IV Q6h). Supportive care. Eliminate precipitating factors

95

What is "Euthyroid Sick"?

Abnormal TFTs (low T4 and T3) commonly found in euthyroid patients with various systemic diseases (starvation, acute infections, acute psychiatric disorders, HIV disease, chronic cardiac, pulmonary, renal, hepatic and neoplastic diseases

96

What are the symptoms of hypothyroidism like in elderly patients?

Symptoms may not be as pronounced. Hoarseness, deafness, confusion, dementia, ataxia, DEPRESSION, dry skin, or hair loss

97

What can hyperthyroidism lead to in pregnancy?

Increases the rate of fetal loss. Goal is to maintain euthyroid state

98

Which medication is ok to use for hyperthyroidism in pregnancy?

Previously, PTU preferred because less crosses the placenta when compared with MTM. Both may be used during pregnancy

99

Why does hypothyroidism occur more often in pregnancy?

Pregnant women have lower TSH and FT4 d/t the increased amount of protein in the body

100

How do you treat hypothyroidism in pregnancy?

Treat with T4 prior to pregnancy. DOC: Levothyroxine

101

What should the TSH levels be during each of the trimesters of pregnancy?

1st: 0.1-2.5, 2nd: 0.2-3, 3rd: 0.3-3

102

What are the consequences of having hypothyroidism in pregnancy?

Increased risk of premature birth. Low birth weight. Questionable neurocognitive defects. Miscarriage. Gestational HTN