L12 (Thyroid Hormones)

Question 1

Thyroid gland is composed of follicles. Follicles are comprised of ___ and ___ cells.

Answer 1

Colloid and follicular cells

Question 2

True or False: Thyroid hormone synthesis requires adequate iodine intake

Answer 2

True

Question 3

Where does iodide trapping occur (via: NIS)?

Answer 3

Follicular cell

Question 4

Where is thyroglobulin synthesized?

Answer 4

Follicular cells

Question 5

Once made, where is TG sent to?

Answer 5

Colloid cell

Question 6

True or False: Thyroglobulin contains a large number of amino acid serines

Answer 6

False - Thyroglobulin contains a large number of amino acid tyrosines

Question 7

___ is the backbone for thyroid hormone synthesis

Answer 7

Thyroglobulin

Question 8

True or False: Thyroid hormones are made while tyrosine is not a part of the TG

Answer 8

False - Thyroid hormones are made while tyrosine IS part of the TG!!

Question 9

What protein/transporter allows iodide to leave the follicular cell and enter into the colloid?

Answer 9

Pendrin

Question 10

Where it T3/T4 stored?

Answer 10

Colloid cell

Question 11

Three roles of Thyroperoxidase (TP)?

Answer 11

1) Oxidation of Iodide
2) Iodination of Tyrosine
3) Coupling of Iodotyrosines

Question 12

True or False: Storing large amount of thyroid hormones in the colloid enhances the ability of one to survive acute I- deficiency

Answer 12

True

Question 13

Which trophic hormone stimulates synthesis and secretion of thyroid hormone?

Answer 13

TSH

Question 14

True or False: Once thyroid hormone is secreted, iodide from any MIT/DIT is recycled and T3 and T4 enter the circulation

Answer 14

True

Question 15

True or False: Stress inhibits TRH-TSH-Thyroid Gland-T3/T4 pathway

Answer 15

True

Question 16

What activates the TRH-TSH-Thyroid Gland-T3/T4 pathway?

Answer 16

Temperature and diurnal rhythm

Question 17

True or False: Thyroid hormone is an amino-acid derivative hormone with steroid-like characteristics

Answer 17

True

Question 18

Which has a longer 1/2 life: T3 or T4?

Answer 18

T4

Question 19

Where are Type 1 and 2 Deiodinase enzymes found?

Answer 19

Type 1: Liver and kidney
Type 2: Brain and muscle

Question 20

Function of Type I and II Deiodinase enzymes?

Answer 20

Converts T4 to T3

Question 21

Role of Type III Deiodinase?

Answer 21

Converts T4 to rT3 (inactive)

Question 22

Most T3 is produced at the tissue level by ___ of T4 by Type _ and _ Deiodinase

Answer 22

de-iodination; Type I and II

Question 23

Which deiodinases work by removing the outer iodide?

Which deiodinase works by removing the inner iodide?

Answer 23

Type I and II

Type III

Question 24

If T4 is deiodinated by Type III Deiodinase, what is produced?

Answer 24

rT3 (inactive)

Question 25

Equal amounts of __ and ___ are made in peripheral tissues How could this be advantageous?

Answer 25

T3/rT3 - Allows for max increase and decrease in T3/rT3

Question 26

The activity of which deiodinase can be altered at the tissue level?

Answer 26

Type I

Question 27

What inhibits Type I deiodinase?

Answer 27

Burns, High GC, starvation, DM

Question 28

Which is more potent: T3 or T4?

Answer 28

T3

Question 29

True or False: prolonged stressors can increase secretion of epinephrine, which increases adipose tissue lipolysis

Answer 29

True

Question 30

Which hormone is required for proper brain development?

Answer 30

Thyroid

Question 31

Thyroid hormone is permissive for what three molecules:

Answer 31

1) Epi 2) Insulin 3) GH

Question 32

Weight loss, constipation, and cold intolerance are features of:

Answer 32

Hypothyroidism

Question 33

Weight gain, tachy, and sweating are features of:

Answer 33

Hyperthyroidism

Question 34

Causes of hyperthyroidism?

Answer 34

1) Graves Disease - TSH receptor antibodies activate TSH receptor 2) Tumor of follicular cells 3) Abnormal TRH/TSH secretion

Question 35

True or False: NIS inhibitor or TP inhibitor can treat hypothyroidism

Answer 35

False - NIS inhibitor or TP inhibitor can treat hyperthyroidism

Question 36

Auto-immune destruction of thyroid gland is present in what condition?

Answer 36

Hashimoto's

Question 37

How is hypothyroidism treated?

Answer 37

Synthetic T4