Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Unit 2 Phys II > L15+16: Thyroid gland > Flashcards

L15+16: Thyroid gland Flashcards

1
Q

the thymus recieves ____ of total blood flow and entire cardiac output in ____

A

2% of total blood flow

1 hour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

at what age is hypothalamus pituitary thyroid axis functional and begin secreting TH

A

12 weeks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

cretinism

A

TH deficiency during gestation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

functional unit of the thyroid

A

follicular cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

lumen contains ____ which ______

A

colloid

storage site for hormones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

thyroglobulin

A

found in the colloid, contains thyroid HH in synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

found in the thyroid and release calcitonin

A

parafollicular cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

hyperthyroid

A

colloid is being reabsorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

hypothyroid

A

decreased colloid reabsorption and thyroid hormone synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

hormone that causes thyrotrophs to release TSH

A

thyrotropin-releasing hormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

thyroid hormone synthesis and release is under feedback control of the

A

hypothalamic pituitary thyroid axis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

TSH release causess

A

TSH is transported to the thyroid gland, binds TSH receptor on follicular cell –> stimulation of all steps in thyroid hormone synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

TSH receptor location

A

basolateral membrane of follicular cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Synthesis of T3 and T4 occurs in _______ and is both _______

A

cytosol of follicular cell and colloid

intracellular and extracellular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

T4 is

A

the major product of synthesis

a prohormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

converts T4 to T3 in the periphery

A

peripheral deiodinases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

deactivate thyroid hormones

A

peripheral deiodinases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

iodide comes from

A

diet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

TSH stimulates

A
  1. Na+ iodide symporter
  2. thryoglobulin
  3. thyroid peroxidase
  4. T3 and T4 synthesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

thyroglobin (Tg)

A

glycoprotein that serves as a scaffold for tyrosine iodination, and thyroid hormone storage
has 132 tyrosine residues
produced in the cytosol of the follicular cell, contains in vesicles, and transferred to the apical membrane for thyroid hormone synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

thyroid peroxidase

A

oxidation of iodide and its incorportion into tyrosine residues to thyroglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Daily intake of iodide

A

400 ug

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

plasma pool of iodide

A

250-750 ug

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

total iodide content of the thyroid

A

7500 ug

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
form of iodide in the thyroid
iodithyronine/thyronines
26
amount of iodide taken up by the thyroid from the plasma
80 ug
27
amount released as HI or free
70-80 ug
28
HI=
hormone-associated iodine
29
what protects from iodide deficiency for about 2 months
large ratio of iodide in the form of hormone: amount turned over daily 100:1
30
tyrosine comes from
endogenous
31
iodide uptake in the follicular cells occurs by
Na+ iodide symporter (NIS) on basal surface | 2 Na+/1 iodide
32
Na+ moves down its concentration gradient which is maintained by
Na+/K+ ATPase
33
how does iodide reach the colloid for production of thyroid hormones
Anoctamin-1 iodide channel on the apical membrane
34
TSH effects on anoctamin-1
opens the channel facilitating leak of iodide into the colloid
35
Low iodide diet effects to keep T3/T4 normal
NIS is increased | Kidneys reduce iodide excretion
36
mutations in NIS or iodide absent from diet cause
hypothyroidism
37
goiter occurs due to
lacking iodide--> enhanced TSH activity having a tropic effect
38
lack of iodide causes
loss of feedback control, effects of TSH go unopposed
39
feedback control in the thyroid occurs due to
T3/T4 negative feedback at the hypothalamus
40
congenital iodide transport defect (ITD)
hypothyroidism goister reduced uptake of radioactive iodide
41
other characteristics of NIS
expressed in gastric mucosa, placenta, and lactating mammary gland for iodide uptake concentrates iodide in milk in lactating gland **not under control of TSH**
42
Grave's disease
autoantibodies are produced against TSH receptor and NIS | bind and stimulate growth of gland
43
Grave's disease causes
hyperthyroidism | goiter caused by TSH stimulation
44
Radioactive iodine uptake (RAIU)
uses tracer dose of 123^I to measure uptake by gamma detection
45
reflects the activity of the thyroid gland
NIS
46
normal RAIU
15% after 6 hours
47
Organifaction defect
when iodine cannot be incorporated inoto tyrosine
48
perchlorate
inhibits NIS
49
transports iodide to the apical membrane and secretes it into the follicular lumen
pendrin
50
thyroid peroxidase
oxidizes iodide to iodine at the apical luminal membrane
51
oxidizing agent used by thyroid peroxidase
H2O2
52
pendrin belongs to the solute carrier family
SLC26A family
53
where else pendrin is expressed
inner ear, important in endocochlear potential and structural development
54
Pendred syndrome
high heterogeneity/variability in mutations of pendrin: goiter during childhood hearing loss
55
low iodide diet + pendred syndrome
goiter and overt hypothyroidism
56
in the colloid, iodine attaches to
a tyrosine on Tg | about 20% are iodinated, 5% will become active thyroid hormone
57
tyrosine + 1 iodide | tyrosine + 2 iodides
monoiodotyrosine (MIT) | diiodotyrosine (DIT)
58
wolff chaikoff effect
iodine metabolism within the cell regulated independently of TSH increased concentration of intrathyroidal iodide inhibits organification temporarily
59
how to make T4
2 diiodotyrosine are coupled
60
how to make T3
couple monoiodotyrosine and diiodotyrosine
61
when are Tg/T3/T4 no longer stored in the colloid
upon stimulation of TSH
62
enzymatically couples MIT and DIT to form T3 and T4
thyroid peroxidase
63
megalin
how follicular cells engulf colloid contains Tg, T3, T4
64
lysosomes
target the engulfed colloid
65
protesases
split T3 and T4 from thyroglobin, which then diffuse into blood
66
intrathyroidal deoiodinase
deiodinates excess MIT and DIT
67
Tg levels in plasma
small amount leaks out normally | higher in hyperthyroidism
68
inhibitors of iodide uptake
perchlorate, thiocyanate
69
inhibitors of oxidation of iodide, organification, coupling
propylthiouracil
70
bind to T3 and T4
*** thyroxine binding globulin (TBG) *** albumin transthyretin lipoprotein
71
T4 structure
2 iodines on both inner and outer rings
72
T3 structure
2 iodines on inner ring, 1 on 3' of outer ring
73
rT3 structure
2 iodines on outer ring, 1 on 3' of inner ring
74
T4 is converted to T3 or rT3 by
deiodinase enzymes
75
deiodinates inner ring of T4 to produce inactive rT3
deiodinase type 3
76
deiodinates outer ring of T4 to produce active T3
deiodinases type 1 and 2
77
deiodinates T3 to produce T2
deiodinase type 3
78
deiodinates rT3 to produce T2
deiodinases type 1 and 2
79
excretion of thyroid hormones
increased solubility by hepatic conjugation to sulfo/glucuronide
80
2 effects of thyroid hormones
1. genomic effects: gene transcription | 2. nongenomic effects: acute, do not require transcriptions
81
nongenomic effects
mostly exerted by T3: rapid effects on ion fluxes (mostly CV): stimulate 1. Ca++ ATPase at plasma membrane and SR - released Ca+, inotropic, increased CO 2. Na+/H+ antiporter in muscle 3. O2 consumption
82
transporter that shows a preference for T4
OATP
83
transporter that shows a preference for T3
MCT
84
MCT8 gene mutations
associated with psychomotor retardation and thyroid hormone resistance
85
transporters for thyroid hormones (4)
1. NTCP 2. OATP 3. LAT 4. MCT
86
NTCP
Na+ taurochlorate contransporting peptide
87
OATP
Organic anion transporting polypeptide | -Na+ independent
88
LAT
L and T type amino acid transporters
89
MCT
monocarboxylate transporters
90
Thyroid hormone receptor is found
intracellularly | associated with thyroid response element (TRE) gene promotor region
91
binding of thyroid hormone to THR
regulates transcription of TRE
92
THR has a greater affinity for
T3: 10x more | 90% of response initiated by T3
93
calorigenic actions of thyroid hormones
increased basal metabolic rate increased body temperature increased oxygen consumption
94
mechanism of calorigenic actions of thyroid hormones
increasing activity of Na+/K+ ATPase
95
Tissues where calorigenic effects of thyroid hormones do not occur
brain gonads spleen
96
Metabolic effects of thyroid hormones
increased glucose absorption from gut increased gluconeogenesis, lipolysis increased protein synthesis and proteolysis (futile cycling) Net degradation of tissue protein: negative nitrogen balance
97
Cardiovascular effects of thyroid hormones
mediated by T3 Increased CO, ventilation chronotropic, inotropic reduced vascular resistance
98
Sympathetic nervous system effects of thyroid hormones
Heterologous up regulation | increased synthesis of B receptors in cardiac/skeletal muscles, adipocytes
99
hypothyroid children will have
delays in bone development, heigh, and mental health that can be attenuated with early thyroxine treatment
100
Thyroid hormones and growth
act synergistically with growth hormone | promote bone formation, maturation of CNS, axonal growth, myelination
101
2 negative feedback mechanisms for thyroid hormone release
1. T3 inhibits TRH release in hypothalamus 2. T3 down regulates TRH on thyrotrophs - T4 converted to T3 also downrgulates
102
T4 is converted to T3 in negative feedback pathways by
T4 pituitary deiodinase | 5', type 2
103
Hypothyroid
decreased carbohydrate, protein, lipid metabolism Increased serum cholesterol Normal levels of serum catecholamines
104
Hyperthyroid
increased carbohydrate, protein, lipid metabolism Decreased serum cholesterol Normal levels of serum catecholamines BUT increased sensitivity to them due to up-regulation of B receptors
105
Adult onset hypothyroidism aka
1. Thyroiditis | 2. Hashimoto's
106
Hyperprolatinemia
occurs with hypothyroidism, low T3/T4 increases TRH secretion, which increases prolactin synthesis
107
Goiter is always present with
Hyperthyroidism | +/- hypothyroidism, so don't make any assumptions
108
Cardiovascular effects of hyperthyroidism
High pulse rate and increased CO | -these are to offset decreased PVR?
109
Hyperthyroidism aka
Graves disease
110
Hyperthyroidism treatment
1. removal 2. Radioactive 131^I destroys gland 3. B blockers 4. Propylthiouracil: decreases T4 to T3 conversion

Unit 2 Phys II (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions