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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
Tyrosine + 1 iodide
Monoiodotyrosine (MIT)
26
MIT + iodide
Diiodotyrosine (DIT)
27
DIT + iodide
T3
28
T3 + iodide
T4
29
____ stimulates thyroglobulin uptake
TSH
30
____ stimulates release of DIT, MIT, T3, T4 out of cell
TSH
31
Biosynthesis depends on products of 3 genes
Sodium iodide symporter Thyroglobulin Thyroid peroxidase
32
Prior to release thyroid hormones are
Cleaved from thyroglobulin
33
>99% of T3/4 are bound to
Plasma proteins
34
Binding to plasma proteins provides
Controlled slow release
35
TSH secretion is inhibited by
High T4 levels
36
Sensitivity of pituitary to TRH depends upon
Intrapituitary T3 levels
37
When T4 serum levels drop what happens to intrapituitary T3
Also goes down
38
TSH controlled by
Hypothalamic thyrotropin-releasing hormone (TRH)
39
TRH is a
Phospholipase C 2nd messenger
40
TRH release stimulated by exposure to
Cold
41
TSH receptors present on surface of
Thyroid follicular cells Works w/ cAMP
42
TSH increases:
- Proteolysis of thyroglobulin - Iodide pump - Iodination of tyrosine - Size, activity, # of thyroid cells
43
Plasma proteins used to transport thyroid hormones
Thyroxine-binding globulin Transthyretin (thyroxine-binding prealbumin)
44
Thyroxine-binding globulin (TBG)
Highest affinity for T3/4 77% T4 bound to TBG
45
TTR has lower affinity for ___ and quantity in blood is ___
T4 Higher
46
TTR does not effectively bind
T3
47
Serum T4 is ____ bound and ____ free
99. 96% bound | 0. 04% free
48
Serum T3 is ____ bound and ____ free
99. 6% bound | 0. 4% free
49
Main action of thyroid hormones
Increase transcription of lots of genes
50
Thyroid hormone effect on cellular metabolic activity
Inc # and activity of mito Inc transport of ions (Na/K pump)
51
Thyroid hormone effect on growth
Promotes growth
52
Hyperthyroid children grow ____ but duration may be _____
Faster; shortened (epiphyseal closure earlier)
53
Thyroid hormones promote growth of ____ especially during _____
Brain; fetal neonatal period
54
Thyroid hormones decrease concentrations of plasma contents:
Cholesterol Phospholipids Triglycerides
55
T3/4 ___ rate of cholesterol secretion into bile and ____ fecal loss
Increase; increase **increase LDL receptors to promote rapid removal
56
Thyroid hormone ____ body weight
Decreases
57
CV effects of thyroid hormone
``` Inc blood flow Inc CO - inc HR and strength Inc systolic BP Dec diastolic BP ```
58
Thyroid hormone on CNS
Inc rapidity of thought (cerebration)
59
Thyroid hormone on skeletal muscle
Enhances contraction
60
Excessive T3/4 ____ muscle contraction
Weakens Bc of excessive protein catabolism
61
Hypothyroidism causes muscles to be ___
Sluggish and contract slowly
62
Characteristic sign of hyperthyroidism is
Fine muscle tremor
63
Hypothyroidism in M/F causes
Loss of libido
64
Excesses of thyroid hormone in men can cause
Impotence
65
Hypo women usually have __ or __
Menorrhagia or polymenorrhea
66
Hyper women can have ____ and ____
Oligomenorrhea and amenorrhea
67
Deficiency in thyroid hormone in children can cause
Stunted growth
68
Thyroid hormones control
Basal metabolic rate
69
Inc in secretion of thyroid hormones exaggerates responses of
Ne/epi in SNS
70
Inc in metabolic rate and body heat suppress TSH release via
Inhibition of TRH Cause acute dec in TSH secretion
71
Both hypo and hyperthyroidism ____ serum cholesterol
Decrease
72
Goiter
Enlargement of thyroid gland
73
Possible to have a goiter and be:
Hypothyroid Euthyroid Hyperthyroid
74
Example of euthyroid goiter
Dietary iodine deficiency
75
Dietary iodine deficiency
T3/4 dec — TSH inc, stimulates growth of thyroid
76
Example of hyperthyroid goiter
Graves disease | Thyroid adenoma
77
Graves’ disease
Thyroid stim by abnormal immunoglobulins against TSH receptor
78
Endemic cretinism
Iodine deficiency in utero
79
Cretinism
Forms of hypothyroid beginning at/before birth
80
Cretinism characterized by
Failure of body growth and intellectual development disorder
81
In cretinism, skeletal growth ______ than soft tissue growth
More inhibited
82
Hashimoto’s disease
Autoimmune disorder Destoyr thyroid Preceded by thyroiditis
83
MC cause of hypothyroidism in US
Chronic lymphocytic thyroidtis (AKA Hashimoto)
84
Reverse T3
3,3’,5’-triiodothyronine (inactive)
85
Myxedema
Generalized nonpitting edema Seen w/ hypothyroid

Endocrinology (11 decks)

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