Physiology of thyroid gland

Question 1

3 parts of thyroid gland

Answer 1

left, right branch, isthmus

Question 2

Things released by thyroid gland

Answer 2

thyroxin, triiodothyronine, calcitonin

Question 3

____ cells surround colloid

Answer 3

follicular

Question 4

____ bring iodide to follicular cells

Answer 4

blood vessels

Question 5

______ release calcitonin

Answer 5

parafollicular cells

Question 6

____ contains thyroglobulin.

Answer 6

Colloid

Question 7

Iodide uptake occurs on the _____ side of the ______ cell via what mechanims?

Answer 7

Basolateral, follicular, Na/I symporter

Question 8

What transport brings iodide into the basolateral side of the follicular cell and what transport brings it out the apical side?

Answer 8

Basolateral: Na/I Symporter
Apical: Pendrin

Question 9

What is iodide trapping?

Answer 9

The process of intracellular accumulation

Question 10

What does iodide do in the colloidal lumen?

Answer 10

It binds tyrosine residues on thryoglobulin

Question 11

____ is a large protein with few tyrosine residues

Answer 11

Thryoglobulin

Question 12

Where is thyroglobulin synthesized?

Answer 12

follicular cells

Question 13

What is thyroid peroxidase and what does it do?

Answer 13

It is on the luminal side of of secretory vescicles (secreteing thyroglobulin). It oxidizes iodide to Io, which is unstable, so that it reacts with thyroglobulin

Question 14

Only ____ tyrosine residues on thyroglobulin are iodinated.

Answer 14

20%

Question 15

What happens after endocytosis of iodinated thyroglobulin?

Answer 15

Hydrolysis forms T3 and T4 in lyso-endosome, iodide is recycled

Question 16

What is the ration of T4 to T3 produced in lyso-endosome?

Answer 16

10:1

Question 17

What percent of T4 is bound? T3?

Answer 17

99.98%; 99.5%

Question 18

Formed T3 and T4 are released into the blood where they immediately ____.

Answer 18

Bind to binding protein, mostly TBG

Question 19

What conditions increase TBG? What does this to do total and free T3 and T4?

Answer 19

Pregnancy, hepatitis, heroin abuse - increases total T3 and T4, but NOT free hormone

Question 20

What conditions decrease TBG? What does this do to total T3 and T4?

Answer 20

Steroids- decreases total but NOT free hormone

Question 21

Compare the half lives of T3 and T4

Answer 21

bound T4- 8 days

bound T3- 24 hrs

Question 22

What is structurally required for active hormone?

Answer 22

2 iodide needed on inner ring and at least 1 on the outside

Question 23

What enzyme catalyzes T4–> T3?

Answer 23

5’/3’mondeoiodinase

Question 24

What enzyme catalyzes T4 to rT3?

Answer 24

5/3 monodeiodinase

Question 25

Metabolism of T3 and rT3?

Answer 25

T2--> T1--> Thyronine

Question 26

What is type 1 deiodinase?

Answer 26

5'/3': T4--> T3--> Liver, Kidney, Thyroid, Primarily responsible for free hormone in the blood

Question 27

What is type 2 deiodinase?

Answer 27

5'/3': T4--> T3--> pituitary (presents T3 to pituitary, a TH regulator, no regulation here during starvation, CNS, placenta

Question 28

What does 5/3 Deiodinase do?

Answer 28

T4--> rT3--> All tissues

Question 29

Where is the thyroid receptor?

Answer 29

nucleus

Question 30

Describe the action of thyroid hormone on target cells

Answer 30

T3 or T4 enter cell--> nuclear target--> THR which dimerizes with RXR and acts direly on DNA to both increase and decrease production

Question 31

____ is the major hormone secreted by the thyroid and carried in the circulation. ____ is the physiologically active form of hormone.

Answer 31

T4; T3

Question 32

Effect of hyperthyroid on basal metabolic rate

Answer 32

Increase (increase O2 consumption and thermogenesis)

Question 33

Effect of hyperthyroid on carb metabolism

Answer 33

increase with no change in glucose in someone with a NORMAL pancreas

Question 34

Effect of hyperthyroid on lipid metabolism

Answer 34

increase

Question 35

Effect of hyperthyroid on serum cholerterol

Answer 35

decrease

Question 36

Effect of hyperthyroid on thermogenesis

Answer 36

increase

Question 37

Effect of hypothyroid on basal metabolic rate

Answer 37

decrease

Question 38

Effect of hypothyroid on carb metabolism

Answer 38

decrease; no change in blood glucose

Question 39

Effect of hypothyroid on protein metabolism

Answer 39

decrease

Question 40

Effect of hypothyroid on lipid metabolism

Answer 40

decrease

Question 41

Effect of hypothyroid on serum cholesterol

Answer 41

increase

Question 42

Effect of hypothyroid on thermogenesis

Answer 42

decrease

Question 43

Describe what happens to Na/K ATPase pump and actin with T3?

Answer 43

Increase, actin--> tachycardia

Question 44

Increase in TRH stimulates what?

Answer 44

thyrotrophs in ant. pit. to increase release of TSH --> T3, T4

Question 45

What role does somatostatin play in regulation of thyroid?

Answer 45

Negative regulation at level of thyrotrophs in ant. pituitary

Question 46

Role of dopamine in thryoid regulation

Answer 46

Negative regulation at level of thyrotrophs in ant pit

Question 47

Role of T3 and T4 in thyroid regulation

Answer 47

Negative regulation on Thyrotrophs and TRH

Question 48

How does TSH increase thyroid secretion?

Answer 48

Increases activity of NIS (iodide uptake), stimulates iodination of thyroglobulin in follicular lumen, stimulates conjugation of iodinated tyrosines to generate T3 and 4, increase endocytosis of iodinated tyrosines to generate T3 and 4, stimulate proteolysis of iodinated thyroglobuin in lysoendosomes, increase secretion of T4 and T4 into circulation, exerts growth factor effects on the thyroid cells increasing their size and number

Question 49

Is TH important in development?

Answer 49

Yes- no sure why but low levels can be seen in dwarfism

Question 50

LOOK OVER LAST FEW SLIDES IF PATHO NOT COVERED IN FUTURE LECTURES

Answer 50

do it