The Thyroid Gland And Thyroid Disease

Question 1

What shape is the thyroid gland?

Answer 1

Butterfly shaped.

Question 2

How many lobes does the thyroid gland have?

Answer 2

Two.

Question 3

Where is the thyroid gland found?

Answer 3

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

Question 4

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

Answer 4

The isthmus.

Question 5

How much does the thyroid gland weigh?

Answer 5

Around 30 grams.

Question 6

How much blood does the thyroid gland receive per minute?

Answer 6

80ml to 120ml.

Question 7

Where are thyroid hormones synthesized?

Answer 7

Thyrocytes.

Question 8

Where are thyroid hormones exported to?

Answer 8

The colloid.

Question 9

Thyroglobulin and glycoprotein contain what kind of residue?

Answer 9

Tyrosine residue.

Question 10

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

Answer 10

Iodide.

Question 11

Iodide is exported to the colloid by what transporter?

Answer 11

Pendrin.

Question 12

Iodide is incoporated in thyroglobulin by what enzyme?

Answer 12

Thyroid peroxidase.

Question 13

What four things does thyroglobulin produce?

Answer 13

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

Question 14

What is T3 also known as?

Answer 14

Triiodothyronine.

Question 15

What is T4 also known as?

Answer 15

Thyroxine.

Question 16

What is the kDa value of thyroglobulin and glycoprotein?

Answer 16

600 kDa.

Question 17

What does TRH stand for?

Answer 17

Thyrotropin release hormone.

Question 18

What does TSH stand for?

Answer 18

Thyroid stimulating hormone.

Question 19

Where is TRH produced?

Answer 19

In the hypothalamus.

Question 20

What part of the brain does TRH act upon?

Answer 20

The anterior pituitary.

Question 21

What stimulates the release of TSH?

Answer 21

TRH.

Question 22

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

Answer 22

T3 and T4.

Question 23

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

Answer 23

TRH and TSH.

Question 24

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

Answer 24

The inhibition of TRH and TSH.

Question 25

What type of tissues deiodinate T4 to T3?

Answer 25

Peripheral tissues (such as the kidney and liver).

Question 26

Is T3 or T4 the active hormone?

Answer 26

T3.

Question 27

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

Answer 27

Reverse T3 (rT3).

Question 28

What are the purpose of thyroid hormones?

Answer 28

They are essential for normal growth and development.

Question 29

How do thyroid hormones enter cells?

Answer 29

Through different aminoacid transporters.

Question 30

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

Answer 30

Retinoid X receptors (RXRs).

Question 31

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

Answer 31

Mitochondrial respiration proteins.

Question 32

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

Answer 32

Basal Metabolic Rate (BMR).

Question 33

Are thyroid hormones mainly protein bound or protein unbound?

Answer 33

Protein bound.

Question 34

What type of globulin carries most of T3 and T4?

Answer 34

Thyroxin binding globulin.

Question 35

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

Answer 35

Albumin and pre-albumin.

Question 36

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

Answer 36

0.02%.

Question 37

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

Answer 37

0.2%.

Question 38

What is the half-life of a T4 hormone?

Answer 38

5 to 7 days.

Question 39

What is the half-life of a T3 hormone?

Answer 39

1 to 2 days.

Question 40

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

Answer 40

Unbound.

Question 41

What is the total plasma concentration of the T3 hormone?

Answer 41

1 to 2.9 nmol/L.

Question 42

What is the total plasma concentration of the T4 hormone?

Answer 42

60 to 150 nmol/L.

Question 43

What is the free plasma concentration of the T3 hormone?

Answer 43

3 to 9 pmol/L.

Question 44

What is the free plasma concentration of the T4 hormone?

Answer 44

9 to 26 pmol/L.

Question 45

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

Answer 45

99.98%.

Question 46

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

Answer 46

99.66%.

Question 47

What are the major pathways of degradation of thyroid hormones?

Answer 47

1. Deiodination and metabolism in tissues. | 2. They are conjugated in the liver and excreted in bile.