thyroid hormones

Question 1

what are 2 main thryroid hormones

Answer 1

T3 and T4

Question 2

what are substrates and enzymes to make T3 and T4

Answer 2

thyroglobulin > peroxidase

Question 3

how to tell if thyroid is active

Answer 3

active- small follicles - cuboidal cells

inactive - large follicles - abundant colloid

Question 4

what are steps to make T3/4

Answer 4

1. transport I into colloid
2. attach I to thyroglobulin
3. phagocytose T3/4
4. back into blood

Question 5

what is iodine requirment

Answer 5

150ug/day

Question 6

how does T3/4 circulate

Answer 6

protein bound (TBG, albumin, transthyretin)

Question 7

what up-regs thyroid binding proteins

Answer 7

1. estrogen and preg.
2. methadone/heroin
3. tranquiizers

Question 8

what down regs. thyroid binding proteins

Answer 8

1. glucocorticoids
2. androgens
3. anti-cancer drugs

Question 9

which thyroid hormone is more active and which is more common

Answer 9

T3 more potent, but T4 more volume

Question 10

where does T3 come from

Answer 10

13% thyoid

87% is deiodinated T4

Question 11

what removes iodine

Answer 11

deiodinase enzyme

Question 12

how does T3/4 work

Answer 12

hydrophobic and passes through cell membrane to bind to receptor, which then bind to DNA

Question 13

what are thyroid hormone receptors

Answer 13

a and B genes: TRa1, TRa2, TRB1 (everywhere)

TRB2 (brain)

Question 14

effects of THs

Answer 14

1. Na/K ATP ase - Na out/ K in
2. increased O2
3. heat gen, sweating
4. weight loss
5. incr. resp
6. increased CV
7. increased metabolism

Question 15

TH CNS effects

Answer 15

1. increased dev.
2. increased B-andrenergic receptors
3. faster reflexes

Question 16

TH growth effects

Answer 16

1. pubertal growth spurt

2. allows GH function

Question 17

what is TH feedback

Answer 17

-ve to pit and and hypo - TRH and TSH

Question 18

what inhibs TRH

Answer 18

1. stress

2. TH

Question 19

what inhibs TSH

Answer 19

1. dopamine,
2. somatostatin
3. glucocorticoids
4. TH

Question 20

what happens in low iodine

Answer 20

can’t make T3/4 so get high TRH and TSH and goiter

Question 21

what are Sx of hypothyroidism

Answer 21

1. lethargy
2. fatigue
3. cold-intolerance
4. weakness
5. hairloss

Question 22

what happens in graves disease

Answer 22

antibody produced that binds to TSH receptor and massive TH results