Endocrinology 12

Question 1

What are the basic functional units of the thyroid?

Answer 1

Thyroid follicles

Question 2

What do the follicles contain in their center?

Answer 2

Colloid

Question 3

What does colloid contain?

Answer 3

The storage form of the steroid hormone

Question 4

What is the colloid surrounded by?

Answer 4

A single layer of epithelial cells/follicular cells

Question 5

What is the colloid and follicular cells like in a resting state?

Answer 5

In a resting state the follicular cells are small and the colloid is large because its storing the hormone

Question 6

What is the colloid and follicular cells like in a acting state?

Answer 6

The colloid in the center is smaller because hormones are being secreted and the follicular cells are large

Question 7

Where are parafollicular cells found?

Answer 7

In between the thyroid follicles

Question 8

What are parafollicular cells/c-cells the source of?

Answer 8

Calcitonin

Question 9

What amino acid are thyroid hormones derived from?

Answer 9

Tyrosine

Question 10

What does Tyrosine bind to in the thyroid?

Answer 10

Iodine

Question 11

What is Monoiodotyrosine (MIT) or diiodotyrosine?

Answer 11

An intermediate molecule that forms when tyrosine binds to one or two iodine

Question 12

What are the active Thyroid hormones?

Answer 12

• Triiodothyronine (T3)

* Tetraiodothyronine (thyroxine, T4)

Question 13

How Does Iodide get from the blood to the thyroid?

Answer 13

By active transport

Question 14

What is Thyroglobulin?

Answer 14

A large glycoprotein that contains tyrosine units

Question 15

What are MIT and DIT formed on?

Answer 15

The backbone of the thyroglobulin molecule

Question 16

What can give T3?

Answer 16

Coupling of MIT and DIT

Question 17

What can give T4?

Answer 17

Coupling of DIT and DIT

Question 18

Where are T3 and T4 stored?

Answer 18

In the colloid

Question 19

Which thyroid hormone is there a greater amount of in the colloid?

Answer 19

T4

Question 20

What is the basolateral side of the follicular cell facing?

Answer 20

Blood vessels

Question 21

What is the apical membrane of the follicular cell facing?

Answer 21

The colloid

Question 22

What pump brings iodine from the blood into the follicular cells?

Answer 22

The sodium iodide pump couples the movement of sodium out of the blood with the movement of iodine

Question 23

What happens once iodide is in the follicular cell?

Answer 23

It leaves the cell through the apical membrane and moves into the colloid

Question 24

What is thyroglobulin secreted from and where does it go?

Answer 24

It is secreted from follicular cells into the colloid

Question 25

What is Thyroglobulin?

Answer 25

A long chain of amino acids (a protein) with tyrosine residues

Question 26

What does the oxidized iodide in the colloid do?

Answer 26

Combines with tyrosine residues in the thyroglobulin molecule

Question 27

What is the catalyst for thyroglobulin tyrosine and iodine combining?

Answer 27

Peroxidase

Question 28

what makes up the bulk of the colloid?

Answer 28

Thyroglobulin with MITs and DITs

Question 29

What movement is required for hormones to be secreted from the thyroid?

Answer 29

They have to move from the colloid through the cell and into the blood through endo and exocytosis

Question 30

What removes the MIT and DIT from thyroglobulin to be T3 and T4?

Answer 30

Lysosomes

Question 31

In what form are T3 and T4 mainly found in the blood?

Answer 31

A bound form to a plasma protein (they are rarely in a free form)

Question 32

What are the characteristics of a hormone in the bound form?

Answer 32

They are not active

Question 33

What does T4 act largely as?

Answer 33

A precursor for T3

Question 34

Where are thyroid hormone receptors found?

Answer 34

In the cell nucleus bound to genetic material

Question 35

Which thyroid hormone binds more strongly to the receptor?

Answer 35

T3

Question 36

What is the half life of thyroid hormones?

Answer 36

1-7 days