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Endocrinology > Exam 2 Material > Flashcards

Exam 2 Material Flashcards

0
Q

What do follicles in thyroid contain?

A

Cavities
Follicular cells
Parafollicular cells

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1
Q

What kind of cells does parathyroid gland have?

A

Chief cell

Oxyphil cell

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2
Q

Five functions of thyroid hormones

A

Important for normal growth and development
Maintain metabolic stability in adults
Have general rather than tissue specific effect
Require dietary iodide for their synthesis
Peripheral tissues convert T4 to T3, providing additional regulatory step of thyroid hormone levels

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3
Q

Role of thyroid hormones in bone

A

Essential for bone growth and development
Activates osteoclast and osteoblast activities
Deficiency during childhood affects growth
In adult excess thyroid hormone levels associated with increased risk of osteoporosis

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4
Q

Role of TH in cardiovascular system

A

Has cardiac ino tropic and chronotropic effects
Increases cardiac output and blood volume
Decreases systemic vascular resistance

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5
Q

Role of TH on adipose tissue

A

Induces white adipose tissue differentiation, lipogenic enzymes, and intracellular accumulation
Stimulates adipocyte cell proliferation
Stimulates uncoupling proteins
Uncoupled oxidative phosphorylation

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6
Q

Role of TH in liver

A

The regulates triglyceride and cholesterol metabolism, as well as lipoprotein homeostasis. Also modulates cell proliferation and mito respiration.

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7
Q

Role of TH in pituitary

A

Regulates synthesis of pit. Hormones
Stimulates GH production
Inhibits TSH

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8
Q

TH role in brain

A

Controls expression of genes involved in myelination, cell differentiation, migration and signaling. Thyroid hormone is necessary for axonal growth and development.

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9
Q

Describe TH mechanism

A

TH goes to intracellular receptor, transcription of specific gene
Increases protein synthesis, which leads to both cell growth and maturation and and cellular respiration increase.
Cellular respiration leads to increased oxygen consumption and metabolism rate. Cell growth and maturation lead to increased food intake and increased oxygen consumption and metabolism rate. The latter leads to both increased cardiac output and ventilation and increased thermogenesis.

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10
Q

How does thyroxin influence fatty acid release from adipose tissue

A

If thyroxin binds with epinephrine, it will lead to enhanced release of fatty acids.

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11
Q

Inter follicular connective tissue

A

Tissue between follicles

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12
Q

What is inside follicles

A

Colloid

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13
Q

What is inside colloid

A

Gelatinous thyroglobulin

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14
Q

Difference between over active and under active thyroid epi cell

A

Under active
Decreased, flattened epi. cells and large colloid reserve
Over active
Tall, columnar epi cells and little colloid (shrunken)

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15
Q

How does TDH stimulate thyroid cells

A

It stimulates colloid to be endocytosed into cells

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16
Q

How does hormone in thyroglobulin get into bloodstream.

A

Thyroglobulin is Exocytosis into colloid, where it is iodinated. Then it is endocytosed in colloid droplets that are taken up by lysosomes that digest the thyroglobulin and release the T4 and T3 into the bloodstream

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17
Q

Capillaries into which TH flows are

A

Fenestrated

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18
Q

What in lysosomes digests thyroglobulin

A

Acid hydrolases

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19
Q

What receptor does TSH activate

A

7TM G protein linked receptor

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20
Q

What effects does TSH have on follicular cell

A

Early effects
Adenylate Cyclase
Endocytosis of colloid
Mito respiration and cell metabolism

Late effects
Iodide uptake
Protein synthesis
DNA replication and mitotic activity

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21
Q

What teo things does TSH receptor activate

A

Adenylate Cyclase

Phospho lipase C

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22
Q

What does TDH activation of adenylate Cyclase cause

A 
Camp synthesis
Transmembrane ion fluxes (sodium, iodine, calcium binds calmodulin)
Protein kinase activation
Phosphorylation
Iodination of thyroglobulin
Colloid droplets in cell
Cellular metabolism
Protein synthesis and rna turnover
Iodine in
DNA synthesis
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23
Q

Two precursors of thyroid hormones

A

Monoiodothyrosine

Diiodothyrosine

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24
Which thyroid hormones are biologically acitve? Inactive?
T4 andT3 active | T2 and reverse T3 inactive
25
Where is T3 synthesized
It is secreted by thyroid, but mostly formed peripherally by T4 deiodination
26
Iodine pathways
``` ECF to thyroid and urine Thyroid to ECF and hormone pool Hormone pool to tissues Tissues to Gi tract and iodine pool GI tract to iodine pool and stool ```
27
Synthesis and Iodination of thyroglobulin
Amino acids enter for protein synthesis Incorporate mannose Incorporate galactose Through Golgi, send vesicle to Exocytosis to colloid Iodide enters cell through iodide transporter Iodide oxidized in cell Iodide sent to colloid, where it binds with thyroglobulin
28
Reabsorption and digestion of thyroglobulin
Thyroglobulin endocytosed into cell in colloid droplets that are taken up by lysosome. Acid hydrolase a in lysosome digest droplet and release t4 and T3, which exit into bloodstream through fenestrated capillaries
29
Size of thyroglobulin
MW660000
30
How many subunits does thyroglobulin have
Two
31
How many tyrosine residues does thyroglobulin have
125
32
How much of thyroglobulin is iodine
One percent
33
Thyroid peroxidase
TPO | Large MW membrane protein located on apical domain of follicular cells
34
What two anions block active transport of I ion into epi cell
CLO4- | SCN-
35
Two transporters on epi basolateral membrane
Na+I- symport | NaKpump
36
Apical microvilli
Found on apical membrane of follicular cell
37
What transporter is on apical membrane
Pendrin I-, Cl- transporter (sodium ion independent)
38
How does TPo iodinate thyroglobulin
Enzyme takes I ion and tyr-protein, binds itself to iodide, binds iodide to protein and recycles itself
39
What decreases efficiency of TPO
If iodide already bound
40
How to make T4 or T3
Take two thyroglobulin molecules and TPO DiIodinate both molecules Bind them If only mono iodinate second molecule, becomes T3
41
Intermediate in t4 synthesis
Quinolone ether intermediate
42
How does iodine level regulate proportion of T4 and t3
If low levels of iodide, more t3. If not, t4
43
How does diet regulate levels of t3
T3 decreases with fasting or starvation This leads to decreased metabolic rate Calorie conservation
44
Where is a lot to t4 converted to t3
Liver and kidneys
45
What do iodothyronine deiodinases contain in their active sites
Selenocysteine
46
Deiodination site of three deiodinases
1-5' and 5 2-5' 3-5
47
Physiological roles of three deiodinases
1. Circulate t3' inactivate t4 and t3, degrade rt3 2. Intracellular t3 in pit, brain, brown adipose tissue 3. Inactivate t3 and t4
48
Tissue location of three deiodinases
1. Liver, kidney, thyroid, and brain 2. Pit, brain, brown adipose tissue, skeletal and cardiac muscle 3. Brain, placenta, skin
49
Substrate preference for three deiodinases
1. Rt3>t4>t3 2. T4=>t3 3. T3>t4
50
Inhibition by propylthyouracil in the deiodinases
1. Sensitive 2. Resistant 3. Resistant
51
Response to TH excess by three deiodinases
1. Increase 2. Decrease 3. Increase
52
Which three proteins bind to TH in circulation
Thyroxin binding globulin Transthyretin Albumin (largest, greatest binding capacity)
53
Thyroxin secretion and feedback mechanism
At hypothalamus Down, somatostatin and dopamine downregulated TSH release TRH upregulates it At pituitary Glucocorticoids decrease TSH release Estrogens increase it At thyroid TDH upregulates TH release, both, and both bound and free Bound and free TH downregulate TSH from pituitary Also downregulate TRH in hypothalamus
54
Two types of cells in parathyroid
Chief cell | Oxyphil cell
55
What is in and around follicles of thyroid
Cavity, where colloid is Follicular cell around colloid Para follicular cell
56
Five functions of thyroid hormones
Normal growth and development Maintain adult metabolic stability Have general rather than tissue specific effect Require dietary iodide for synthesis Peripheral tissues concert T4 to T3, providing addl regulatory steps of thyroid hormone levels
57
How does TH affect bone 4
1. Essential for bone growth and devt 2. Activates osteoclast and osteoblast activity 3. Deficiency during childhood affects growth 4. In adults, excess thyroid hormone levels associated with increased risk of osteoporosis
58
TH and cardiovascular system 3
1. Has cardiac ino tropic and chronotropic effects 2. Increases cardiac output and blood volume 3. Decreases systemic vascular resistance
59
TH and adipose tissue 4
1. Induces white adipose tissue differentiation, lipogenic enzymes, and intracellular lipid accumulation 2. Stimulates adipocyte cell proliferation 3. Stimulates uncoupling proteins 4. Uncoupled oxidative phosphorylation
60
TH and liver
TH regulates triglyceride and cholesterol metabolism Lipoprotein homeostasis Modulates cell proliferation and mitochondrial respiration
61
TH and pituitary
Regulates synthesis of pituitary hormones Stimulates GH production Inhibits TSH
62
TH and brain
Controls expression of genes involved in myelination, cell differentiation, migration, and signaling. Thyroid hormone is necessary for axonal growth and development.
63
Steps for synthesis of thyroid hormone
1. Iodide uptake and per oxidation 2. Thyroglobulin biosynthesis and secretion into lumen 3. Intra colloidal modification of thyroglobulin - Iodination of tyrosine residues - formation of iodothyronines by coupling of specific iodothyrosyl residues
64
Secretion and metabolism steps of TH
1. Storage of iodinated thyroglobulin as a colloid 2. Endocytosis of iodinated thyroglobulin and fusion with lysosomes 3. Cleavage of iodinated thyroglobulin to TH in lysosome 4. TH release and metabolism (deiodination)
65
Of which is there more production? T4 or T3
Twice as much t4 as t3
66
How much of T3 is made in thyroid? t4
20%, 100%
67
Distribution of T3 and T4 in liters
T3 40 liters | t4 10 liters
68
Half life of T3 and T4
t3- 0.75 days | T4- 7.0 days
69
How does TH affect transcription and protein synthesis
Low dose of T3 given to rat without thyroid Increase in nuclear RNA -increase in rRNA and polysome formation - increase in protein synthesis
70
How do TH receptors work
Hormone activated transcription factors
71
What binding domains do TH receptors have
DNA binding | TH binding
72
Six TH receptors
``` TRbeta1 TRbeta2 TRbeta3 TRalpha1 TRalpha2 TRalpha3 ```
73
TRbeta 1 location
Liver, kidney, thyroid
74
TRbeta2 location
Pituitary, hypothalamus, retina and inner ear
75
TRbeta3 location
Heart and kidney
76
TRalpha1 location
Heart, bone and brain
77
Do TRalpha2 and 3 bind hormone!
No

Endocrinology (21 decks)

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