Thyroid Physiology

Question 1

The thyroid is supplied by the

Answer 1

superior and inferior thyroid artery and vein

Question 2

__ is the biologically active thyroid hormone

Answer 2

T3

Question 3

__ doesn’t play a physiologic role but is a tumor marker for ___ thyroid cancer

Answer 3

Calcitonin; medullary

Question 4

Thyroid increases basal ____ rate in all tissues except

Answer 4

metabolic; brain, testes, spleen

Question 5

Thyroid effect on CV system

Answer 5

increases expression of alpha myosin heavy chains, which increases contractility and heart rate

Question 6

Thyroid effect on heme

Answer 6

increases oxygen dissociation

Question 7

Congenital hypothyroidism symptoms (aka cretinism)

Answer 7

severe mental retardation and dwarfism

Question 8

T4 and T3 are made where

Answer 8

T4 exclusively in the thyroid gland, 80% of T3 converted from T4 outside the thyroid

Question 9

_ has the major regulatory feedback on the hypothalamus and pituitary

Answer 9

T3

Question 10

__ is required to synthesize thyroid hormone

Answer 10

iodine

Question 11

This group needs more iodine and this other group need the most iodine

Answer 11

pregnant women, breast feeding women

Question 12

Thyroglobulin is made by what and stored by

Answer 12

thyroid follicular epithelial cells; colloid

Question 13

What is penderin

Answer 13

a iodine/cl transporter which move iodine to the membrane-colloid interface

Question 14

Two reactions TPO catalyzes

Answer 14

Oxidation of Iodide to iodine and iodination of the thyroid hormone (adding iodine to it)

Question 15

TPO gene stimulated by

Answer 15

TSH

Question 16

Why do you have more T4 in the thyroid

Answer 16

it’s made 10x faster than T3

Question 17

T4, T3 and uncoupled DIT/MIT are bound to what in the colloid

Answer 17

Thyroglobulin

Question 18

MIT and DIT combination is catalyzed by

Answer 18

TPO

Question 19

What happens when the thyroid gland is stimulated by TSH

Answer 19

colloid is taken to the follicular cells by pinocytosis and there the thyroglobulin is cleaved off T3/T4 by proteases

Question 20

Iodines are cleaved from unused DIT and MIT

by an enzyme called

Answer 20

thyroid deiodinase

Question 21

Reverse T3 is ____ (activity)and made from ___

Answer 21

inactive; T4 iodine cleaved off the inner ring

Question 22

Over 70% of T4/T3 are abound to

Answer 22

TBG

Question 23

Half lives of T4/T3 and its significance

Answer 23

T4- 8 days, T3- one day, T4 is biologically very available

Question 24

Estrogen and Hepatitis do what to TBG

Answer 24

increase it

Question 25

How does pregnancy affect free T3 levels

Answer 25

doesn’t affect em, achieves steady state

Question 26

__ is the best measurement for thyroid function

Answer 26

TSH

Question 27

Thyroid remains connected to foramen cecum by the __, which regresses at 8 weeks

Answer 27

thyroglossal duct