Lecture 17: Thyroid Hormones 1

Question 1

Thyroid gland: Single layered circular follicles are comprised of

Answer 1

Cuboidal endocrine cell surrounded by basement membrane

Question 2

Lumen of follicle of Thyroid Gland is made of what material?

Answer 2

Colloid

Question 3

Thyroid gland: Newly synthesized, stored hormones are attached to what in the lumen of follicle?

Answer 3

Thyroglobulin

Question 4

What is absorbed into follicular cells under stimulation

Answer 4

Colloidal thyroid hormone

Question 5

Parafollicular cells (C cells) secrete what

Answer 5

Calcitonin

Question 6

Thyroxine is

Answer 6

T4

Question 7

Triiodythyronine is

Answer 7

T3

Question 8

What is the active thyroid form?

Answer 8

T3

Question 9

Large amounts of what are required for thyroid hormone synthesis?

Answer 9

Iodine

Question 10

Synthesis of thyroid hormones is intracellular or extracellular?

Answer 10

Partially both

Question 11

What is the major hormone secreted, and what is the biologically active thyroid hormone?

Answer 11

T4 = Major hormone
T3 = Biologically active

Question 12

In order to synthesize thyroid hormones, first need to synthesize protein molecule called

Answer 12

Thyroglobulin

Question 13

To synthesize thyroglobulin, you need

Answer 13

Tyrosine

Question 14

Where is thyroglobulin synthesized?

Answer 14

In rough ER + golgi of follicular cells

Question 15

After thyroglobulin synthesis, it is put into

Answer 15

Follicular lumen

Question 16

How are thyroid hormones bound?

Answer 16

Using peptide linkages

Question 17

Iodide is transported from blood into follicular epithelial cells via which transporters?

Answer 17

2Na/I symporter

Question 18

Iodide is transported across apical membrane into colloid of follicle via ____ and oxidized iodine

Answer 18

Pendrin

Question 19

What incorporates iodine into tyrosines at specific sites in thyroglobulin

Answer 19

Thyroid peroxidase

Question 20

The coupling reaction of tyrosine and iodine results in

Answer 20

MIT and DIT

Question 21

Two DIT molecules =

Answer 21

T4

Question 22

One DIT + one MIT =

Answer 22

T3

Question 23

Excessively high levels of dietary iodide will

Answer 23

Suppress activity of 2 Na/1 I pump

Question 24

Thyroglobulin is stored in follicles as ______ until stimulation for release of thyroid hormones

Answer 24

Colloid

Question 25

The stimulus for release of thyroid hormones is

Answer 25

Thyroid stimulating hormone

Question 26

Retrieval of thyroglobulin from follicle lumen into endocrine cell via

Answer 26

Endocytosis

Question 27

Cell membranes form

Answer 27

Pseudopods

Question 28

Lysosomes fuse with colloid droplet and release

Answer 28

T3, T4, free MIT, and free DIT

Question 29

Deiodinase enzyme

Answer 29

Deionizes MIT and DIT to conserve iodide and recycle

Question 30

Thyrotropin releasing hormone is released from

Answer 30

Hypothalamus

Question 31

TRH causes release of

Answer 31

Thyroid stimulating hormone from anterior pituitary

Question 32

TSH causes release of

Answer 32

T4 and T3 from thyroid gland

Question 33

Negative feedback of T4 and T3 to

Answer 33

Anterior pituitary and hypothalamus

Question 34

Large circulating pool of

Answer 34

T4

Question 35

Small pool and short half life

Answer 35

T3

Question 36

What effects of age and dog breed size have on circulating concentrations?

Answer 36

Higher levels in small breed dogs
Decrease with age

Question 37

~10% of T4 and T3 is bound to

Answer 37

Thyroxine-binding globulin

Question 38

Transthryetin

Answer 38

Lower affinity for T4, readily transfers T4 to target cells

Question 39

TRH is a what kind of hormone

Answer 39

Tripeptide

Question 40

TSH is what kind of hormone

Answer 40

Glycoprotein hormone with two subunits