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Thyroid Hormones (L12) Flashcards

1
Q

Thyroid hormone controls BMR, which stands for ____

A

basal metabolic rate

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2
Q

The thyroid is composed of follicles. Follicles are composed of ___ and ____

A

follicular (thyroid) cells and colloid cells

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3
Q

Colloid (protein) solution contains
____ and stored _____

A

thyroglobulin (TG) ; thyroid hormone

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4
Q

Thyroid Hormone Synthesis requires adequate intake of ____

A

Iodine

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5
Q

Where does iodide trapping occur? Via what transporter?

A

Iodide trapping occurs within follicular cells via NIS (Na/Iodide Symporter)

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6
Q

What is the ‘backbone’ for thyroid
hormone synthesis?

A

Thyroglobulin (TG)

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7
Q

What cell type produces thyroglobulin?
Where is TG release into?

A

Follicular cells
TG is released into colloid

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8
Q

True or False: TG contains large numbers of amino acid serines

A

False - TG contains large numbers of amino acid tyrosines

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9
Q

What are two ways that thyroid hormones are made?

A

1) Incorporating iodine onto tyrosines
2) Coupling iodinated tyrosines

Note: In both cases, it occurs while tyrosine is part of thyroglobulin

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10
Q

What does this image display?

A

Coupling of Iodinated Tyrosines

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11
Q

What does this image display?

A

Incorporating Iodine onto Tyrosine

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12
Q

What molecule moves I2 from the follicular cell into the colloid?

A

Pendrin

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13
Q

Which enzyme incorporates iodine onto tyrosines, causing TG to have just tyrosines to having MIT and DIT and, eventually, T4 and T3?

A

TP (Thyroperoxidase)

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14
Q

What is mostly made in the thyroid gland: T3 or T4?

A

T4

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15
Q

What are the three roles of TP (thyroperoxidase)?

A

1) oxidation of iodide
2) iodination of tyrosine
3) coupling of iodotyrosines

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16
Q

_____ allows for conversion of I- to I2

A

Thyroperoxidase

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17
Q

Large amount of thyroid hormones are stored in the ___, which enhances one’s ability to survive acute iodine deficiency

A

colloid

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18
Q

Which trophic hormone stimulates the synthesis and secretion of thyroid hormone?

A

TSH

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19
Q

True or False: TSH promotes gland growth and cell integrity

A

True

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20
Q

Endocytosis will be facilitated by ___

A

TSH

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21
Q

As 2nd messengers are generated, it promotes ____ of thyroid hormone and TF molecule, which leads to T3/4

A

As 2nd messengers are generated, it promotes endocytosis of thyroid hormone and TF molecule, which leads to T3/4 secretion

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22
Q

When thyroid hormone is secreted, iodide from any MIT/DIT is ___

A

recycled

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23
Q

Once T4 and T3 are made, they enter into ___

A

circulation

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24
Q
A

Delete

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25
Stress (physical, starvation, and infection) inhibits ___
TRH (thyroid-releasing hormone)
26
What two factors increase TRH?
1) Diurnal Rhythm 2) Temperature
27
If an excess of thyroid hormones is made, what two molecules are inhibited?
TRH and TSH
28
True or False: TSH is made in the hypothalamus while TRH is made in the anterior pituitary
True
29
True or False: Thyroid hormone is an amino acid derivative hormone with steroid-like characteristics
True
30
What is the half life of T3 and T4?
T3 = 1.0 days T4 = 6.2 days
31
Most T3 is produced at the tissue level by de-iodination of ___
T4
32
Type 1 and Type 2 Deiodinase produces ___
T3
33
Which type of deiodinase produces rT3?
Type 3 Deiodinase
34
Where are Type 1 Deiodinases found? Where are Type 2 Deiodinases found?
Type I: Liver and Kidney Type II: Muscle and Brain
35
Most T3 is produced at the tissue level by de-iodination of T4 by which types of deiodinases? How?
Type 1 and Type 2 Deiodinases Via: removal of outer iodide
36
Which is more potent: T3 or T4
T3
37
At the tissue level, T4 can also be deiodinate by which type of deiodinase to make rT3 (inactive)?
Type 3 Deiodinate (removes innher iodide)
38
Equal amounts of what two molecules are made in the peripheral tissues? Why might this be advantageous?
T3 and rT3 -Allow for maximal increase and maximal decrease in T3 and rT3
39
T4 is converted to T3 via Type ___ Deiodinase T4 is converted to rT3 via Type __ Deiodinase
T4 is converted to T3 via Type 1 Deiodinase T4 is converted to rT3 via Type 3 Deiodinase
40
True or False: The activity of Type 1 Deiodinase can be altered at the tissue level
True
41
What inhibits Type 1 Deiodinase?
1) Starvation 2) Cancer 3) Renal failure 4) Burns 5) Trauma
42
Prolonged stressors can increase the secretion of what two molecules?
1) Epinephrine - increases adipose tissue lipolysis 2) Cortisol - increases protein breakdown
43
If Type 1 Deiodinase is inhibited, T3 levels ___ while inactive rT3 levels ___ Why might this be helpful during severe illness or starvation?
decrease; increase - LIMITS T3 induced substrate breakdown in tissues
44
True or False: Prolonged stressors can increase the secretion of thyroid hormones
False - prolonged stressors can decrease the secretion of thyroid hormones (T4>T3)
45
T4 is converted to ___ at the tissue level
rT3
46
True or False: Brain, spleen, and gonads have few receptors for thyroid hormones so their BMR and temperature do not change
True
47
Which thyroid receptor isoforms is more prevalent in the brain (alpha or beta)? Which thyroid receptor isoform is more prevalent in the liver, muscle, and pituitary gland?
Brain = Alpha Liver, muscle, and pituitary = Beta
48
What are the overall roles of thyroid hormone in body metabolism?
1) Energy 2) ATP synthesis 3) Heat production 4) Calorie supply 5) O2 consumption
49
True or False: Thyroid hormone involves protein synthesis
True
50
What are two intracellular effects of thyroid hormone?
1) Increase BMR 2) Increase synthesis and activity of Na/K ATPase
51
What are three systemic effects of thyroid hormone?
1) Mobilization of substrates for ATP generation by cells 2) Increased delivery of substrate to cells 3) Increased delivery of O2 to cells; CO2 removal from cells
52
Intracellular effects of thyroid hormone?
Increased synthesis of: - metabolic enzymes - mitochondrial enzymes - substrate transporters - Na/K ATPase Increased metabolism of susbtrates: - heat and ATP production - O2 consumption Increased activity of Na/K ATPase - heat production
53
True or False: Once T4 is converted to T3, T3 enters the nucleus and increases synthesis of - metabolic enzymes - mitochondrial enzymes - substrate transporters - Na/K ATPase
True
54
True or False: thyroid decreases availability of substrate for cells
False - Thyroid hormone increases the availability of substrates for cells
55
___ substrates increases food intake while ___ substrates store
Exogenous substrates; endogenous
56
How do thyroid hormones increase HR and SV?
Increase number of beta-adrenergic receptors in the heart
57
True or False: Thyroid hormones decrease CO
False - thyroid hormones increase CO
58
True or False: Thyroid hormones increase delivery of substrates to cells
True
59
Thyroid hormones increase respiratory rate. How does this affect O2 delivery and removal of CO2?
Increase O2 delivery and removal of CO2
60
Thyroid hormone is permissive for full physiological effects of: ______ ______ ______
Epinephrine Insulin GH
61
True or False: Thyroid hormone is required for normal in utero brain development
True
62
How do you evaluate thyroid abnormalities?
TSH, T3/T4 Evaluate symptoms
63
Symptoms associated with hyperthyroidism? Symptoms associated with hypothyroidism?
Hyperthyroidism: weight loss, tachy, sweating, and diarrhea Hypothyroidism: weight gain, brady, cold intolerance, and constipation
64
Graves' Disease is associated with _____
hyperthyroidism
65
____: TSH receptor antibodies that activate TSH receptor
Graves' Disease: TSH receptor antibodies that activate TSH receptor
66
True or False: Hyperthyroidism can be due to tumor of follicular cells or abnormal TRH/TSH secretion
True
67
Four ways to treat hyperthyroidism?
1) Inhibit iodide trap using thiocynate or perchlorate 2) Inhibit TP activity 3) Surgically remove some thyroid gland 4) Thyroid gland ablation
68
Hasimoto's Disease is an autoimmune disease, which results in ___
hypothyroidism
69
Cause of Hypothyroidism?
1) Hashimoto's 2) Surgical removal 3) Hypothalamic/pituitary failure 4) Low iodine in diet
70
Treatment for Hypothyroidism?
Exogenous thyroid hormone (synthetic T4)

Physiology II (23 decks)

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