Regulation of Thyroid Hormone Synthesis Flashcards

1
Q

Thyroid hormone is a _________-derived hormone.

A

tyrosine

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2
Q

The skeleton of thyroid hormone is ___________.

A

thyronine

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3
Q

The thyroid hormone is made hydrophobic by ___________.

A

its ether linkage

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4
Q

The full name of T4 is ________________.

A

3,5,3’,5’–tetraiodothyronine (also called thyroxine)

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5
Q

The full name of T3 is _________________.

A

3,5,3’–triiodothyronine

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6
Q

The thyroid has a copious blood supply. One of the reasons this is thought to be so is _____________.

A

that iodide is a trace element in water, and in the natural world we would need to absorb as much iodide from the water as possible

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7
Q

How is iodide absorbed by thyroid follicular cells?

A

By a sodium/iodide symporter (the intracellular sodium is then pumped back out through a Na/K antiporter)

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8
Q

The thyroid follicular cells secretes ____________ into the lumen of the thyroid.

A

thyroglobulin

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9
Q

Thyroglobulin is used entirely within _____________.

A

the thyroid gland

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10
Q

Each thyroglobulin protein contains approximately ____________ tyrosine residues that can be used to make T4.

A

20 (although there are many more tyrosine residues)

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11
Q

Thyroglobulin is made in a non-iodinated form that then gets _________________.

A

secreted by the thyroid follicular epithelium into the follicular colloid

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12
Q

Thyroglobulin gets iodinated in the ______________.

A

colloid and then taken up by endocytosis back into the thyroid follicular epithelium

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13
Q

T3 and T4 bind _______________.

A

nuclear receptors

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14
Q

Low levels of T3 induce a metabolic shift to ____________.

A

anabolism

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15
Q

High levels of T3 induce a metabolic shift to ______________.

A

catabolism

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16
Q

High levels of thyroid hormone stimulate which adrenergic receptor?

A

Beta-1

17
Q

TSH regulates which points of thyroid production and release?

A
  • Growth of follicular cells
  • Transporters
  • Thyroperoxidase
  • Thyroglobulin
  • Organification of iodide (putting free iodide onto protein)
  • Endocytosis of thyroglobulin from the colloid
18
Q

The primary constituent of the colloid is _______________.

A

thyroglobulin

19
Q

Where is thyroperoxidase?

A

In the colloid, bound to the membrane

20
Q

What are DIT and MIT?

A

Diiodotyrosine and monoiodotyrosine –these couple to form triiodothyronine

21
Q

Where are T4 and T3 cleaved from thyroglobulin?

A

In follicular lysosomes

22
Q

_____________ has a longer half-life.

A

T4 (another reason thyroxine is given pharmaceutically)

23
Q

Why does thyrotoxicity mimic catecholamine overdose?

A

Because thyroid hormone potentiates the effects of catecholamines

24
Q

List five effects of thyroid hormone.

A
  • Increased basal metabolic rate
  • Potentiation of catecholamine effects
  • Promotes linear growth throughout childhood
  • Promotes brain development throughout childhood
  • Promotes anabolic effect at low doses and catabolic effect at high doses