Hypothyroidism Flashcards

1
Q

What are the muscles that overlie the Thyroid gland?

A

SCM
Omohyoid
Sternohyoid

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2
Q

How do you palpate the thyroid gland?

A

Superior to inferior, from the hyoid cartilage, have them swallow, and compare

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3
Q

Why use your stethoscope with hypothyroidism?

A

May hear a bruit

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4
Q

sign***

A
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5
Q

What is the first step of thyroid hormone synthesis?

A

Trapping of Iodide by the Na/I symporter

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6
Q

What is the second step of thyroid hormone synthesis?

A

Trapping–TPO catalyzes iodine oxidation to thyroglobulin

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7
Q

What is the third strep of thyroid hormone synthesis?

A

COupling–MITs and DITs

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8
Q

What is the Jod Basedow effect?

A

Initial increase in organification with iodide synthesis

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9
Q

What is the Wolff-Chaikoff effect?

A

Very high concentrations of iodide actually inhibit organification of T4

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10
Q

What is the Escape phenomenon with thyroid function?

A

AT extremely high iodide concentrations, organification will resume

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11
Q

How is T4 converted to T3?

A

5’ Deiodination in the periphery by deiodinase

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12
Q

What are the two subunits of TSH? What is the function of each

A

Alpha subunit

Beta subunit = active part

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13
Q

What happens to prolactin levels with TRH levels?

A

May increase. Thus hypothyroidism may cause prolactin

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14
Q

Why is it that a woman who is hypothyroid may have high levels of prolactin?

A

TRH causes increase in prolactin

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15
Q

What is the major output of the thyroid gland?

A

T4 (95% of secretion)

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16
Q

What is the process that converts T4 to T3 in the periphery?

A

5’ Deiodination

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17
Q

What is the half life of T4? T3?

A
T4 = 7 days
T3 = 1 day
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18
Q

True or false: thyroid hormone bound to proteins have no biological effect?

A

True

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19
Q

What is the purpose of transporting thyroid hormone bound to protein?

A

Allows for a reserve and a buffer

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20
Q

What percent of T4 and T3 are “free” in the serum?

A
T4 = 0.04%
T3 = 0.4%
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21
Q

What is the main protein that binds thyroid hormone?

A

Thyroid binding globulin

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22
Q

What are the labs that are evaluated for thyroid issues?

A

Free T4 and FT3 vs T4

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23
Q

What are the factors that may increase TBG levels? (2)

A

Estrogen (pregnancy, BCP)

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24
Q

What are the factors that decrease TBG? (3)

A

Systemic illness
Glucocorticoids
Cirrhosis

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25
Q

What is the main lab test to assess for thyroid function? Why?

A

TSH levels are the most sensitive and are less prone to fluctuations

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26
Q

What is the relationship to TSH with hypo/hyperthyroidism?

A

Inverse

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27
Q

Why is T3 not a good lab test to order?

A

Prone to fluctuations

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28
Q

Which is better: T4 levels or total thyroid hormone?

A

T4

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29
Q

What is the relationship between TSH and FT4?

A

Inverse

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30
Q

What happens to TSH levels as you progress from hypo to hyperthyroidism?

A

Decreases

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31
Q

What are the tests that assess for autoimmune thyroid dzs? What is the problem with this?

A

Thyroperoxidase Ab

Super sensitive to any sort of autoimmune disease

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32
Q

What are the three ab that can be obtained for suspected autoimmune thyroid dz?

A

Thyroperoxidase
Thyroglobulin
Thyrotropin ab

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33
Q

What is the ab that is detected with Grave’s disease?

A

Thyrotropin receptor ab

34
Q

What is subclinical hyperthyroidism/hypothyroidism?

A

T3/T4 levels are normal, but TSH levels are low/high respectively

35
Q

What happens to TSH levels and T3/T4 levels with secondary/central hypothyroidism?

A

Low TSH

Low T4/T3

36
Q

What happens to TSH levels and T3/T4 levels with primary hyperthyroidism?

A

low TSH

High T3/T4

37
Q

What happens to TSH levels and T3/T4 levels with central hyperthyroidism?

A

High TSH

High T4/T3

38
Q

What happens to TSH levels and T3/T4 levels with Primary hypothyroidism?

A

High TSH, low T3/T4

39
Q

Who is thyroiditis usually seen in?

A

Postpartum women

40
Q

What are the drugs that can cause hypothyroidism?

A
  • Iodine
  • Sunitinib
  • ANtithyroids
41
Q

What are the ssx for hypothyroidism?

A

Non pitting edema
Pericardial effusion
Bradycardia

42
Q

What are the GI ssx of hypothyroidism?

A

Decreased motility

Ascites

43
Q

What are the reproductive abnormalities with hypothyroidism?

A

Menstrual abnormalities
Decreased fertility
Prolactin levels high

44
Q

What are the odd neuro ssx of hypothyroidism?

A
  • Carpal tunnel syndrome

- Decreased reflexes, slowed relation phase

45
Q

What are the metabolic ssx of hypothyroidism? (3)

A
  • Hypercholesterolemia
  • Hypertriglyceridemia
  • Weight gain
46
Q

What is the most common cause of hypothyroidism?

A

Hashimoto’s thyroidits

47
Q

What is Hashimoto’s thyroiditis?

A

Autoimmune-mediated destruction of the thyroid

causes lymphocytic infiltration of the thyroid

48
Q

What is the Fhx like with Hashimoto’s?

A

Family h/o autoimmunity

49
Q

In whom does Hashimoto’s usually occur in? What are the PE findings?

A

Women (7:1)
Goiter
Bosselated feel of the thyroid

50
Q

What are the TSH levels in hashimoto’s?

A

High

51
Q

What are the TPO ab levels with Hashimoto’s?

A

Elevated, but this is not a requirement

52
Q

How specific is TPO elevation for Hashimoto’s?

A

Not super

53
Q

What is the classic echo findings of Hashimoto’s?

A

Heterogenous appearance

54
Q

What is iodine-relater hypothyroidism?

A

Iodine deficiency may cause a lack of fuel for hormone sythesis

55
Q

What are the lab and PE findings with iodine-related hypothyroidism?

A

Increased TSH levels

Goiter formation

56
Q

Excess Iodine can cause what?

A

Hyper or hypothyroidism

57
Q

True or false: most patient demonstrate the escape phenomenon

A

True

58
Q

What are the sources of Iodine induce hypothyroidism?

A

Amiodarone
Supplements
Radiocontrast for CTs

59
Q

What is the treatment for hypothyroidism?

A

Replacement with Levothyroxine

60
Q

What is the dosage for Levo thyroxine?

A

1.5 mcg/kg/day

61
Q

In whom should levo-thyroxin be started at low levels with?

A

Cardiac pts

62
Q

What are the factors that influence L-Thyroxine levels?

A

Foods

TBG levels

63
Q

When is treatment for hypothyroidism indicated?

A

TSH more than 10, or maybe if they’re symptomatic

64
Q

What is the timeframe for f/u with starting thyroid replacement? Why?

A

6 weeks

Half Life of TSH is ~7 days, so not reached steady state

65
Q

When should patients taking TSH recheck their levels?

A

If patients switch brands, or starts BCP, prego

66
Q

What is the MOA of liothyronine? When is this recommended?

A

Synthetic T3

Not recommended, but may be used for cancer pts

67
Q

What is Armour thyroid?

A

Dessicated porcine or bovine thyroid (T3 and T4)

68
Q

What happens to thyroid needs with pregnancy?

A

Increases throughout pregnancy–may need up to 150% of dose

69
Q

What are the contributing factors for the increase in thyroid hormones in prego? (3)

A

Weight gain
Increasing TBG levels
Increased 5’ deiodination

70
Q

What is myxedema coma?

A

Mental status change
Hypothermia
Hypoglycemia
Hypotension

71
Q

In whom is myxedema coma occur in?

A

Older women, usually precipitated by CVA

72
Q

What is the treatment for myxedema coma?

A

Supportive

IV thyroxine replacement

73
Q

What is the treatment for thyroid cancer?

A

Pts are usually surgically hypothyroid—T4 is used to replace them, and to suppress TSH levels

74
Q

What is the treatment for secondary hypothyroidism?

A

Pituitary or hypothalamic insult

75
Q

Why is TSH not reliable for secondary hypothyroidism? What should be followed?

A

Pituitary may be the issue, and thus may be normal–need to use T4 levels

76
Q

Should T4 be used to shrink nodules?

A

No

77
Q

Should T4 be used to lose weight?

A

No

78
Q

Should T4 be used to treat depression?

A

No

79
Q

Should T4 be used to lower cholesterol?

A

No

80
Q

What should be done with pregnant women with hypothyroidism?

A

Check TSH levels when pregnancy begins, every 4-6 weeks, and after delivery