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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
Q

Which thyroid hormones are biologically acitve? Inactive?

A

T4 andT3 active

T2 and reverse T3 inactive

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25
Q

Where is T3 synthesized

A

It is secreted by thyroid, but mostly formed peripherally by T4 deiodination

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26
Q

Iodine pathways

A 
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
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27
Q

Synthesis and Iodination of thyroglobulin

A

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

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28
Q

Reabsorption and digestion of thyroglobulin

A

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

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29
Q

Size of thyroglobulin

A

MW660000

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30
Q

How many subunits does thyroglobulin have

A

Two

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31
Q

How many tyrosine residues does thyroglobulin have

A

125

32
Q

How much of thyroglobulin is iodine

A

One percent

33
Q

Thyroid peroxidase

A

TPO

Large MW membrane protein located on apical domain of follicular cells

34
Q

What two anions block active transport of I ion into epi cell

A

CLO4-

SCN-

35
Q

Two transporters on epi basolateral membrane

A

Na+I- symport

NaKpump

36
Q

Apical microvilli

A

Found on apical membrane of follicular cell

37
Q

What transporter is on apical membrane

A

Pendrin I-, Cl- transporter (sodium ion independent)

38
Q

How does TPo iodinate thyroglobulin

A

Enzyme takes I ion and tyr-protein, binds itself to iodide, binds iodide to protein and recycles itself

39
Q

What decreases efficiency of TPO

A

If iodide already bound

40
Q

How to make T4 or T3

A

Take two thyroglobulin molecules and TPO
DiIodinate both molecules
Bind them
If only mono iodinate second molecule, becomes T3

41
Q

Intermediate in t4 synthesis

A

Quinolone ether intermediate

42
Q

How does iodine level regulate proportion of T4 and t3

A

If low levels of iodide, more t3. If not, t4

43
Q

How does diet regulate levels of t3

A

T3 decreases with fasting or starvation
This leads to decreased metabolic rate
Calorie conservation

44
Q

Where is a lot to t4 converted to t3

A

Liver and kidneys

45
Q

What do iodothyronine deiodinases contain in their active sites

A

Selenocysteine

46
Q

Deiodination site of three deiodinases

A

1-5’ and 5
2-5’
3-5

47
Q

Physiological roles of three deiodinases

A
  1. Circulate t3’ inactivate t4 and t3, degrade rt3
  2. Intracellular t3 in pit, brain, brown adipose tissue
  3. Inactivate t3 and t4
48
Q

Tissue location of three deiodinases

A
  1. Liver, kidney, thyroid, and brain
  2. Pit, brain, brown adipose tissue, skeletal and cardiac muscle
  3. Brain, placenta, skin
49
Q

Substrate preference for three deiodinases

A
  1. Rt3>t4>t3
  2. T4=>t3
  3. T3>t4
50
Q

Inhibition by propylthyouracil in the deiodinases

A
  1. Sensitive
  2. Resistant
  3. Resistant
51
Q

Response to TH excess by three deiodinases

A
  1. Increase
  2. Decrease
  3. Increase
52
Q

Which three proteins bind to TH in circulation

A

Thyroxin binding globulin
Transthyretin
Albumin (largest, greatest binding capacity)

53
Q

Thyroxin secretion and feedback mechanism

A

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
Q

Two types of cells in parathyroid

A

Chief cell

Oxyphil cell

55
Q

What is in and around follicles of thyroid

A

Cavity, where colloid is
Follicular cell around colloid
Para follicular cell

56
Q

Five functions of thyroid hormones

A

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
Q

How does TH affect bone 4

A
  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
Q

TH and cardiovascular system 3

A
  1. Has cardiac ino tropic and chronotropic effects
  2. Increases cardiac output and blood volume
  3. Decreases systemic vascular resistance
59
Q

TH and adipose tissue 4

A
  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
Q

TH and liver

A

TH regulates triglyceride and cholesterol metabolism
Lipoprotein homeostasis
Modulates cell proliferation and mitochondrial respiration

61
Q

TH and pituitary

A

Regulates synthesis of pituitary hormones
Stimulates GH production
Inhibits TSH

62
Q

TH and brain

A

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

63
Q

Steps for synthesis of thyroid hormone

A
  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
Q

Secretion and metabolism steps of TH

A
  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
Q

Of which is there more production? T4 or T3

A

Twice as much t4 as t3

66
Q

How much of T3 is made in thyroid? t4

A

20%, 100%

67
Q

Distribution of T3 and T4 in liters

A

T3 40 liters

t4 10 liters

68
Q

Half life of T3 and T4

A

t3- 0.75 days

T4- 7.0 days

69
Q

How does TH affect transcription and protein synthesis

A

Low dose of T3 given to rat without thyroid
Increase in nuclear RNA
-increase in rRNA and polysome formation
- increase in protein synthesis

70
Q

How do TH receptors work

A

Hormone activated transcription factors

71
Q

What binding domains do TH receptors have

A

DNA binding

TH binding

72
Q

Six TH receptors

A 
TRbeta1 
TRbeta2
TRbeta3
TRalpha1
TRalpha2
TRalpha3
73
Q

TRbeta 1 location

A

Liver, kidney, thyroid

74
Q

TRbeta2 location

A

Pituitary, hypothalamus, retina and inner ear

75
Q

TRbeta3 location

A

Heart and kidney

76
Q

TRalpha1 location

A

Heart, bone and brain

77
Q

Do TRalpha2 and 3 bind hormone!

A

No

Endocrinology (21 decks)

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