Bio L2 Thyroid Hormones Flashcards

1
Q

What molecule inhibits iodide uptake in thyroid?

A

Thiocyanate

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2
Q

What enzyme coverts iodide to iodine?

A

Thyroid peroxidase (TPO)

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3
Q

What is organification reaction?

A

Iodination of tyrosine residues (at position 3 first)

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4
Q

What releases when 2 DIT couple

A

Thyroxine and alanine

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5
Q

TPO is inhibited by?

A

Methimazole & PTU

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6
Q

What are PD and MCT

A

PD: pendrin (transports iodide to colloid cavity)
MCT: mono carboxyl transporter (transports hormones into blood)

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7
Q

T4:T3 ratio? Which is more efficient?

A

30:1 , T3

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8
Q

What are the carriers ?

A

Albumin, thyroxine-binding globulin (alpha), prealbumin (only T4)

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9
Q

Which form affects regulation?

A

Free form, negative feedback inhibits TSH

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10
Q

What effect does T3 have on cells?

A

T3 receptors are in the nucleus, they stimulate metabolic activities (production of proteins)
Increases Na/K ATPase —> more ATP needed

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11
Q

Effects on CHO metabolism

A

Liver glycogenolysis, intestinal glucose absorption, potentiate epinephrine glycogenolysis effect

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12
Q

Effect on fat

A

Stimulates hormone sensitive lipase in fats, stimulates FA oxidation, reduces cholesterol as it promotes its oxidation to bile acids

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13
Q

Regulation of thyroid hormones

A

1) Hypothalamic-hypophyseal-thyroid axis
2) Auto-regulation by iodide content (low=increase sensitivity to TSH & higher T3 than T4)
3) Peripherally by hormone conversion to inactive rT3

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