Lect 22 - Thyroid

Question 1

The colloid is made up of what type of macromolecule?

Answer 1

glycoprotein

Question 2

Parafollicular cells are also called what?

Answer 2

C cells

Question 3

TRH acts on which cells? Where are they located?

Answer 3

Thyrotrophs in the anterior pituitary

Question 4

How many amino acids make up thyrotropin releasing hormone?

Answer 4

three

Question 5

Thyrotropin releasing hormone is secreted ________.

Answer 5

constant

Question 6

Which second messengers does TRH work through?

Answer 6

IP3/DAG/Ca

Question 7

Which second messengers does TSH work through?

Answer 7

cAMP and PLC

Question 8

What is the breakdown of T3, T4, and rT3 in the blood?

Answer 8

90% T4, 9% T3, and 1% rT3

Question 9

How is iodine taken in through the diet?

Answer 9

by iodide or iodate

Question 10

What is the daily requirement of iodine?

Answer 10

150 micrograms

Question 11

If you have an iodine deficiency how does the body compensate?

Answer 11

Increasing TSH levels leading to goiter

Question 12

About how many tyrosine molecules does thyroglobulin have?

Answer 12

~70

Question 13

What protein works with iodine on the basolateral membrane of follicular lumen cells in the thyroid?

Answer 13

sodium-iodide symporter

Question 14

Thyroglobulin is present on the follicular membrane bound to which enzyme?

Answer 14

thyroperoxidase

Question 15

Iodine is oxidized by TPO in a process known as what?

Answer 15

Organification

Question 16

Molecules of MIT and DIT are joined in a process known as what?

Answer 16

Conjugation

Question 17

What is bad about cabbage?

Answer 17

It inhibits iodine trapping in the thyroid

Question 18

What does TSH stimulation do in terms of thyroglobulin?

Answer 18

Taken up by lysoendosomes from the follicular lumen

Question 19

What are three inhibitors of steps in the thyroid hormone synthesis pathway?

Answer 19

1) PTU
2) high iodine concentration (competitive inhibitor)
3) perchlorate/thiocyanate

Question 20

The TSH-receptor complex is clinically significant in what way?

Answer 20

Antibodies in the body can attack it, either stimulating or inhibiting it

Question 21

When autoantibodies inhibit the TSH-receptor complex, what is the disease called?

Answer 21

Hashimoto’s

Question 22

When autoantibodies stimulate the TSH-receptor complex, what is the disease called?

Answer 22

Grave’s

Question 23

A high iodine concentration is clinically helpful in inhibiting uptake of what?

Answer 23

radioactive iodine

Question 24

How is T4 converted to T3?

Answer 24

5’-deiodinase

Question 25

Thyroid hormone works synergistically with which hormones to promote bone formation?

Answer 25

growth hormone and somatomedin

Question 26

What is another name for somatomedin C?

Answer 26

IGF-1 (insulin-like growth factor 1)

Question 27

Thyroid hormone has tons of effects on target tissues. What are some of these effects?

Answer 27

1) increased insulin synthesis and increased blood glucose
2) decreased body weight
3) increased CO
4) increased BMR
5) increased oxygen consumption and blood flow to tissues
6) muscle protein breakdown

Question 28

What are the effects of TH on the heart?

Answer 28

1) stimulation of beta-1 adrenoreceptors
2) increased activity of sodium-potassium ATPase
3) increased activity of SR calcium ATPase
4) increased CO thru increased SV and HR

Question 29

The main effects of TH on muscle, fat, and liver are?

Answer 29

1) liver: increased glucose production
2) muscles: increased protein breakdown
3) fat: increased lipolysis

Question 30

About what percentage of T3 and T4 is bound to thyroxine-binding globulin? What is the rest bound to?

Answer 30

70% bound to thyroxine-binding globulin; rest to albumin, transthyretin, and other binding proteins

Question 31

What are the two main causes of hyperthyroidism?

Answer 31

1) Grave’s disease

2) Plummer’s disease aka toxic nodular goiter

Question 32

What are three consequences of Grave’s disease?

Answer 32

1) exophthalmos
2) pretibial myxedema
3) thyroid storm

Question 33

What is one treatment for Grave’s disease and how does it work?

Answer 33

iodide; works as a competitive inhibitor

Question 34

What are three causes of hypothyroidism?

Answer 34

1) Hashimoto’s thyroiditis
2) thyroidectomy
3) iodide deficiency

Question 35

What are two causes of hypothyroidism in newborns?

Answer 35

1) iodine deficiency in diet

2) placental transfer of TSH Abs

Question 36

What is the cause of myxedema?

Answer 36

accumulation of GAGs (such as hyularonic acid)

Question 37

An increase in TRH causes an increase in TSH as well as?

Answer 37

Prolactin