Thyroid Gland

Question 1

Where is the thyroid gland

Answer 1

Under the thyroid cartilage In the throat

Question 2

What artery’s go to the thyroid gland

Answer 2

Superior thyroid artery
Inferior thyroid artery

Question 3

Where does the superior thyroid artery come from

Answer 3

Internal carotid artery

Question 4

Where does the inferior thyroid artery come from

Answer 4

Subclavian artery

Question 5

What is the isthmus

Answer 5

The layer of connective tissue that would join the two lobes of the thyroid gland together

Question 6

Where are the thyroid hormones made

Answer 6

The follicular cells
Some also happens in the lumen
Intracellular and extracellular

Question 7

How much iodine is needed daily by an adult

Answer 7

150 ug

Question 8

What is the Wolff-chain off effect

Answer 8

Auto regulation of iodine without the TSH
When too little, decreased amount of thyroid synthesis
When too much, decreased activity of the thyroid peroxidase enzyme

Question 9

What is thyroid binding globulin

Answer 9

What most of the circulating T4 hormone would bind to

Question 10

What is transthyerin protein

Answer 10

Protein that would bind to T4 and would transport it to the cerebrospinal fluid

Question 11

What pathway does TRH induce when it’s binds to the receptor on the thyrotroph (APG)

Answer 11

The PLC
IP3
releases more ca2+
Exocytosis of the TSH

Question 12

What pathway does the TSH induce when it binds to the follicular cell wall

Answer 12

Adenyl cyclase
ATP to CAMP
Energy for the hormones to be made

Question 13

What happens in thyroid hormone receptor binding

Answer 13

T4 TO T3
Corepressor would originally block transcription (binds to the RXR and TR)
The T3 binds to the TR and would be accompanied by a co-activator
Corepressor released
Transcription no longer blocked

Question 14

What are the effects of the thyroid hormone

Answer 14

Increased O2 consumption
Increased growth and development
Increased metabolism (and the degen of substances)

Question 15

What is the difference between the T4 and T3

Answer 15

T4 is most abundant
T3 is most active

Question 16

Where is the dietary iodine absorbed

Answer 16

The GI tract

Question 17

Where would the iodine be extracted

Answer 17

The thyroid gland and the KIDNEY

Question 18

What are the main stages in the generation of the thyroid hormones

Answer 18

Oxidation (I- to I2 by TPO and h2o2)
Organification
Coupling reaction

Question 19

What is thyroglobulin

Answer 19

Main backbone in the hormones

Question 20

Where is thyroglobulin made

Answer 20

The ER

Question 21

What happens to the thyroglobulin

Answer 21

Made in ER
To the Golgi
Packed ina vesicles
Goes for the Lumen of the thyroid follicle (extracellular)

Question 22

How does I- get into the cell

Answer 22

By iodine trapping
Na+/I- Symporter

Question 23

What fixes the I- and the thyroglobulin

Answer 23

Thyroid perixidase enzyme
Makes the hormone
(Uncoupling)

Question 24

How is the hormone broken down

Answer 24

Endocytosis back to the cell
In colloid droplets
Lysosomes allow proteolysis (making the T4 and T3)
and the deionisation (released iodide)

Question 25

What are the thyroid specific deiodinases

Answer 25

D1 D2 and D3

Question 26

What does D1 deiodinase do

Answer 26

Removes the iodine from the inner and outer ring T4 to T3

Question 27

Where does D1 act

Answer 27

Liver Kidney Thyroid

Question 28

What does D2 do

Answer 28

Removes iodine from the outside of the benzene T4 to T3 Thyroid sensor so allows the negative feedback

Question 29

Where does D2act

Answer 29

CNS Pituitary gland Placenta

Question 30

Where does D3 do

Answer 30

Removes iodine from the inner of the benzene T4 to rT3 (so to an inactive form)

Question 31

Where does D3 act

Answer 31

CNS Placenta

Question 32

What happens in organification of the hormones

Answer 32

The I2 would react with the tyrosine Monoidotyrosine or diidotyrosine (MIT OR DIT)

Question 33

What meds to happen to the iodine for it to get absorbed

Answer 33

Iodine needs to be changed to iodide for it to be absorbed But in oxidation would be changed back to the iodine during OXIDATION

Question 34

How would T4 and T3 be made

Answer 34

In uncoupling T4 - DIT + DIT (2 diidotyrosines) T3 - DIT + MIT (monoidotyrosine and diidotyrosine)

Question 35

Where is T4 converted to T3

Answer 35

In the peripheral tissues

Question 36

Where would the thyroid hormones be stored

Answer 36

In the colloid vesicles Would hold a reserve of T4 and T3 Would then be released in to the blood stream when needed

Question 37

Where would TRH bind to

Answer 37

The thyrotrophs of the APG

Question 38

What are the metabolic effects of the thyroid hormones

Answer 38

Increased activity of the Na+/k+ ATPase (increase body temp and the increased BMR) Increased protein, carbohydrates and lipid metabolism (make up, break down, muscle wasting for protein, decreased serum cholesterol for lipids)

Question 39

What do thyroid hormones do to the B1 receptor

Answer 39

Upregulation Increased sensitivity to the catecholamines

Question 40

What are the effects of TSH on the thyroid gland

Answer 40

Increased proteolysis of thyroglobulin Increased rate of iodine trapping Increased iodination of tyrosine to form the thyroid hormones Increased size and secretory activity of the thyroid gland Increased number of thyroid cells plus the change from CUBOIDAL TO COLUMNAR

Question 41

When would the thyroid cells be active

Answer 41

When there epithelium goes from cuboidal to columnar

Question 42

What enzyme would oxidise the iodide to iodine

Answer 42

Thyroid peroxidase