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Tp2. Metabolism, Endocrinology and Haemology > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

Where is the thyroid gland

A

Under the thyroid cartilage In the throat

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2
Q

What artery’s go to the thyroid gland

A

Superior thyroid artery
Inferior thyroid artery

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3
Q

Where does the superior thyroid artery come from

A

Internal carotid artery

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4
Q

Where does the inferior thyroid artery come from

A

Subclavian artery

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5
Q

What is the isthmus

A

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

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6
Q

Where are the thyroid hormones made

A

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

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7
Q

How much iodine is needed daily by an adult

A

150 ug

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8
Q

What is the Wolff-chain off effect

A

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

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9
Q

What is thyroid binding globulin

A

What most of the circulating T4 hormone would bind to

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10
Q

What is transthyerin protein

A

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

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11
Q

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

A

The PLC
IP3
releases more ca2+
Exocytosis of the TSH

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12
Q

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

A

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

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13
Q

What happens in thyroid hormone receptor binding

A

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

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14
Q

What are the effects of the thyroid hormone

A

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

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15
Q

What is the difference between the T4 and T3

A

T4 is most abundant
T3 is most active

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16
Q

Where is the dietary iodine absorbed

A

The GI tract

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17
Q

Where would the iodine be extracted

A

The thyroid gland and the KIDNEY

18
Q

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

A

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

19
Q

What is thyroglobulin

A

Main backbone in the hormones

20
Q

Where is thyroglobulin made

A

The ER

21
Q

What happens to the thyroglobulin

A

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

22
Q

How does I- get into the cell

A

By iodine trapping
Na+/I- Symporter

23
Q

What fixes the I- and the thyroglobulin

A

Thyroid perixidase enzyme
Makes the hormone
(Uncoupling)

24
Q

How is the hormone broken down

A

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

25
Q

What are the thyroid specific deiodinases

A

D1 D2 and D3

26
Q

What does D1 deiodinase do

A

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

27
Q

Where does D1 act

A

Liver
Kidney
Thyroid

28
Q

What does D2 do

A

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

29
Q

Where does D2act

A

CNS
Pituitary gland
Placenta

30
Q

Where does D3 do

A

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

31
Q

Where does D3 act

A

CNS
Placenta

32
Q

What happens in organification of the hormones

A

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

33
Q

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

A

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

34
Q

How would T4 and T3 be made

A

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

35
Q

Where is T4 converted to T3

A

In the peripheral tissues

36
Q

Where would the thyroid hormones be stored

A

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

37
Q

Where would TRH bind to

A

The thyrotrophs of the APG

38
Q

What are the metabolic effects of the thyroid hormones

A

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)

39
Q

What do thyroid hormones do to the B1 receptor

A

Upregulation
Increased sensitivity to the catecholamines

40
Q

What are the effects of TSH on the thyroid gland

A

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

41
Q

When would the thyroid cells be active

A

When there epithelium goes from cuboidal to columnar

42
Q

What enzyme would oxidise the iodide to iodine

A

Thyroid peroxidase

Tp2. Metabolism, Endocrinology and Haemology (16 decks)

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