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Endocrinology > Exam 1: Thyroid > Flashcards

Exam 1: Thyroid Flashcards

1
Q

Thyroid gland location

A

Below larynx on each side of trachea

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2
Q

2 hormones that thyroid gland secretes

A

T4 (93%)

T3 (7%)

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3
Q

T4 AKA

A

Thyroxine

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4
Q

T3 AKA

A

Triiodothyronine

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5
Q

Almost all T4 eventually converted to

A

T3 (in tissues)

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6
Q

Which thyroid hormone is more potent

A

T3 (4x)

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7
Q

Thyroid secretes ____ which decreases blooc Ca2+

A

Calcitonin

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8
Q

Calcitonin opposes action of

A

PTH and vitamin D

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9
Q

Colloid

A

Secretory substance containing thyroglobulin

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10
Q

Thyroglobulin is precursor for

A

T3 and T4

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11
Q

____ required for formation of T3 and T4

A

Iodine

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12
Q

How much iodine must be ingested per week for normal amounts of hormone

A

1mg

Found in table salt

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13
Q

____ of absorbed iodide taken up by thyroid, the rest is ___

A

1/5

Excreted by kidneys

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14
Q

Thyroid composed of large # of ____ filled w/ colloid

A

Follicles

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15
Q

Transport of iodides from blood into follicle requires

A

Sodium iodide symporter

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16
Q

Sodium iodide symporter cotransports

A

1 iodide w/ 2 sodiums

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17
Q

Sodium iodide symporter coupled to

A

Na/K pump

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18
Q

Sodium iodide symporter stimulated by

A

TSH

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19
Q

Before adding iodine to thyroglobulin it combines w/

A

Thyroid peroxidase

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20
Q

Precursor of all thyroid hormones

A

Thyroglobulin

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21
Q

Thyroglobulin is made up of

A

70-130 tyrosine residues

20% iodinated

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22
Q

1st essential step in formation of thyroid hormones

A

Oxidation of iodide

Requires oxidase and H2O2

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23
Q

Thyroid gland can store ____ worth of hormone

A

2-3 months

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24
Q

Organification of thyroglobulin

A

Combining w/ iodide

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25
Q

Tyrosine + 1 iodide

A

Monoiodotyrosine (MIT)

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26
Q

MIT + iodide

A

Diiodotyrosine (DIT)

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27
Q

DIT + iodide

A

T3

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28
Q

T3 + iodide

A

T4

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29
Q

____ stimulates thyroglobulin uptake

A

TSH

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30
Q

____ stimulates release of DIT, MIT, T3, T4 out of cell

A

TSH

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31
Q

Biosynthesis depends on products of 3 genes

A

Sodium iodide symporter
Thyroglobulin
Thyroid peroxidase

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32
Q

Prior to release thyroid hormones are

A

Cleaved from thyroglobulin

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33
Q

> 99% of T3/4 are bound to

A

Plasma proteins

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34
Q

Binding to plasma proteins provides

A

Controlled slow release

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35
Q

TSH secretion is inhibited by

A

High T4 levels

36
Q

Sensitivity of pituitary to TRH depends upon

A

Intrapituitary T3 levels

37
Q

When T4 serum levels drop what happens to intrapituitary T3

A

Also goes down

38
Q

TSH controlled by

A

Hypothalamic thyrotropin-releasing hormone (TRH)

39
Q

TRH is a

A

Phospholipase C 2nd messenger

40
Q

TRH release stimulated by exposure to

A

Cold

41
Q

TSH receptors present on surface of

A

Thyroid follicular cells

Works w/ cAMP

42
Q

TSH increases:

A
  • Proteolysis of thyroglobulin
  • Iodide pump
  • Iodination of tyrosine
  • Size, activity, # of thyroid cells
43
Q

Plasma proteins used to transport thyroid hormones

A

Thyroxine-binding globulin

Transthyretin (thyroxine-binding prealbumin)

44
Q

Thyroxine-binding globulin (TBG)

A

Highest affinity for T3/4

77% T4 bound to TBG

45
Q

TTR has lower affinity for ___ and quantity in blood is ___

A

T4

Higher

46
Q

TTR does not effectively bind

A

T3

47
Q

Serum T4 is ____ bound and ____ free

A
  1. 96% bound

0. 04% free

48
Q

Serum T3 is ____ bound and ____ free

A
  1. 6% bound

0. 4% free

49
Q

Main action of thyroid hormones

A

Increase transcription of lots of genes

50
Q

Thyroid hormone effect on cellular metabolic activity

A

Inc # and activity of mito

Inc transport of ions (Na/K pump)

51
Q

Thyroid hormone effect on growth

A

Promotes growth

52
Q

Hyperthyroid children grow ____ but duration may be _____

A

Faster; shortened (epiphyseal closure earlier)

53
Q

Thyroid hormones promote growth of ____ especially during _____

A

Brain; fetal neonatal period

54
Q

Thyroid hormones decrease concentrations of plasma contents:

A

Cholesterol
Phospholipids
Triglycerides

55
Q

T3/4 ___ rate of cholesterol secretion into bile and ____ fecal loss

A

Increase; increase

**increase LDL receptors to promote rapid removal

56
Q

Thyroid hormone ____ body weight

A

Decreases

57
Q

CV effects of thyroid hormone

A 
Inc blood flow
Inc CO
- inc HR and strength
Inc systolic BP
Dec diastolic BP
58
Q

Thyroid hormone on CNS

A

Inc rapidity of thought (cerebration)

59
Q

Thyroid hormone on skeletal muscle

A

Enhances contraction

60
Q

Excessive T3/4 ____ muscle contraction

A

Weakens

Bc of excessive protein catabolism

61
Q

Hypothyroidism causes muscles to be ___

A

Sluggish and contract slowly

62
Q

Characteristic sign of hyperthyroidism is

A

Fine muscle tremor

63
Q

Hypothyroidism in M/F causes

A

Loss of libido

64
Q

Excesses of thyroid hormone in men can cause

A

Impotence

65
Q

Hypo women usually have __ or __

A

Menorrhagia or polymenorrhea

66
Q

Hyper women can have ____ and ____

A

Oligomenorrhea and amenorrhea

67
Q

Deficiency in thyroid hormone in children can cause

A

Stunted growth

68
Q

Thyroid hormones control

A

Basal metabolic rate

69
Q

Inc in secretion of thyroid hormones exaggerates responses of

A

Ne/epi in SNS

70
Q

Inc in metabolic rate and body heat suppress TSH release via

A

Inhibition of TRH

Cause acute dec in TSH secretion

71
Q

Both hypo and hyperthyroidism ____ serum cholesterol

A

Decrease

72
Q

Goiter

A

Enlargement of thyroid gland

73
Q

Possible to have a goiter and be:

A

Hypothyroid
Euthyroid
Hyperthyroid

74
Q

Example of euthyroid goiter

A

Dietary iodine deficiency

75
Q

Dietary iodine deficiency

A

T3/4 dec — TSH inc, stimulates growth of thyroid

76
Q

Example of hyperthyroid goiter

A

Graves disease

Thyroid adenoma

77
Q

Graves’ disease

A

Thyroid stim by abnormal immunoglobulins against TSH receptor

78
Q

Endemic cretinism

A

Iodine deficiency in utero

79
Q

Cretinism

A

Forms of hypothyroid beginning at/before birth

80
Q

Cretinism characterized by

A

Failure of body growth and intellectual development disorder

81
Q

In cretinism, skeletal growth ______ than soft tissue growth

A

More inhibited

82
Q

Hashimoto’s disease

A

Autoimmune disorder

Destoyr thyroid

Preceded by thyroiditis

83
Q

MC cause of hypothyroidism in US

A

Chronic lymphocytic thyroidtis (AKA Hashimoto)

84
Q

Reverse T3

A

3,3’,5’-triiodothyronine (inactive)

85
Q

Myxedema

A

Generalized nonpitting edema

Seen w/ hypothyroid

Endocrinology (11 decks)

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