Thyroid Flashcards

1
Q

What connects the two lobes of the thyroid?

A

Isthmus

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2
Q

What are the two endocrine cell types in the thyroid?

A

Follicular and parafollicular cells

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3
Q

What are the three hormones secreted by the thyroid?

A

Thyroxine, triiodothyronine, calcitonin

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4
Q

What does the thyroid gland regulate? (8)

A

Breathing, heart rate, central and peripheral nervous system, body weight, muscle strength, menstrual cycles, body temp, cholesterol levels

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5
Q

What element is essential for thyroid hormone synthesis?

A

Iodine

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6
Q

What thyroid component takes up iodide?

A

Sodium-iodide symporters in the thyrocytes

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7
Q

What oxidises iodide?

A

Thyroperoxidase (TPO)

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8
Q

What is iodide incorperated into after it is oxidised and what does this form?

A

Selected tyrosyl residues of thyroglobulin (TG), forming mono and diiodotyrosines

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9
Q

What are mono and diodotyrosines formed from?

A

Oxidised iodide and selected tyrosyl residues of thyroglobulin

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10
Q

What happens to mono- and diodotyrosines?

A

They are couples by TPO to form thyroxine (T4) and triiodothyronine

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11
Q

What is thyroxine formed from?

A

Two diiodotyrosines

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12
Q

What is triiodothyronine formed from?

A

One monodotyrosine and one diiodotyrosine

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13
Q

What does T3 and T4 bind to in the bloodstream?

A

Thyroxine-binding globulin (TBG)

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14
Q

What is the most active form of thyroid hormone?

A

Free T3 (disassociated from TBG)

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15
Q

Is T3 or T4 more active?

A

T3- ten times more active than T4

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16
Q

How is T4 converted to T3?

A

5’-deiodinase in peripheral tissues

17
Q

What are the roles of TPO in thyroid hormone synthesis?

A

Oxidises iodide, and couples the iodotyrosines

18
Q

What is the role of NIS in thyroid hormone synthesis?

A

Uptake of iodide in the thyrocytes