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Clinical Biochemistry > The Thyroid Gland And Thyroid Disease > Flashcards

The Thyroid Gland And Thyroid Disease Flashcards

1
Q

What shape is the thyroid gland?

A

Butterfly shaped.

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2
Q

How many lobes does the thyroid gland have?

A

Two.

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3
Q

Where is the thyroid gland found?

A

At the front of the base of the neck and either side of the trachea.

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4
Q

What piece of thin tissue joins the lobes of the thyroid gland together?

A

The isthmus.

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5
Q

How much does the thyroid gland weigh?

A

Around 30 grams.

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6
Q

How much blood does the thyroid gland receive per minute?

A

80ml to 120ml.

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7
Q

Where are thyroid hormones synthesized?

A

Thyrocytes.

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8
Q

Where are thyroid hormones exported to?

A

The colloid.

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9
Q

Thyroglobulin and glycoprotein contain what kind of residue?

A

Tyrosine residue.

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10
Q

What ion is actively uptaken in the plasma membrane of thyrocytes?

A

Iodide.

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11
Q

Iodide is exported to the colloid by what transporter?

A

Pendrin.

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12
Q

Iodide is incoporated in thyroglobulin by what enzyme?

A

Thyroid peroxidase.

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13
Q

What four things does thyroglobulin produce?

A
  1. T3.
  2. T4.
  3. Mono-iodotyrosine (MIT).
  4. Di-iodotyrosine (DIT).
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14
Q

What is T3 also known as?

A

Triiodothyronine.

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15
Q

What is T4 also known as?

A

Thyroxine.

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16
Q

What is the kDa value of thyroglobulin and glycoprotein?

A

600 kDa.

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17
Q

What does TRH stand for?

A

Thyrotropin release hormone.

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18
Q

What does TSH stand for?

A

Thyroid stimulating hormone.

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19
Q

Where is TRH produced?

A

In the hypothalamus.

20
Q

What part of the brain does TRH act upon?

A

The anterior pituitary.

21
Q

What stimulates the release of TSH?

A

TRH.

22
Q

TSH stimulates the thyroid gland to produce what type of hormones?

A

T3 and T4.

23
Q

A low blood concentration of T3 and T4 stimulates the release of what?

A

TRH and TSH.

24
Q

What does a rise in concentration of unbound T3 and T4 in the blood cause?

A

The inhibition of TRH and TSH.

25
Q

What type of tissues deiodinate T4 to T3?

A

Peripheral tissues (such as the kidney and liver).

26
Q

Is T3 or T4 the active hormone?

A

T3.

27
Q

T4 can be metabolised to a biologically inactive hormone. What is this hormone?

A

Reverse T3 (rT3).

28
Q

What are the purpose of thyroid hormones?

A

They are essential for normal growth and development.

29
Q

How do thyroid hormones enter cells?

A

Through different aminoacid transporters.

30
Q

Thyroid hormones bind specific nuclear receptors dimerizing with what type of receptors?

A

Retinoid X receptors (RXRs).

31
Q

Thyroid hormones stimulate gene expression and synthesis of polypeptides, hormones and enzymes. Give an example of a protein produced by thyroid hormones.

A

Mitochondrial respiration proteins.

32
Q

Thyroid hormones affect metabolism. What specifically within metabolism is affected?

A

Basal Metabolic Rate (BMR).

33
Q

Are thyroid hormones mainly protein bound or protein unbound?

A

Protein bound.

34
Q

What type of globulin carries most of T3 and T4?

A

Thyroxin binding globulin.

35
Q

Name two proteins that thyroid hormones are bound to within the blood.

A

Albumin and pre-albumin.

36
Q

What is the percentage of unbound (free) T4 hormones?

A

0.02%.

37
Q

What is the percentage of unbound (free) T3 hormones?

A

0.2%.

38
Q

What is the half-life of a T4 hormone?

A

5 to 7 days.

39
Q

What is the half-life of a T3 hormone?

A

1 to 2 days.

40
Q

Which is more important for the biological effects of hormones - Bound T3 and T4 concentrations or unbound T3 and T4 concentrations?

A

Unbound.

41
Q

What is the total plasma concentration of the T3 hormone?

A

1 to 2.9 nmol/L.

42
Q

What is the total plasma concentration of the T4 hormone?

A

60 to 150 nmol/L.

43
Q

What is the free plasma concentration of the T3 hormone?

A

3 to 9 pmol/L.

44
Q

What is the free plasma concentration of the T4 hormone?

A

9 to 26 pmol/L.

45
Q

What is the extent of protein binding of T4 in percentage?

A

99.98%.

46
Q

What is the extent of protein binding of T3 in percentage?

A

99.66%.

47
Q

What are the major pathways of degradation of thyroid hormones?

A
  1. Deiodination and metabolism in tissues.

2. They are conjugated in the liver and excreted in bile.

Clinical Biochemistry (1 decks)

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