Lecture 6 - Thyroid

Question 1

T3/4 synth:

1. Iodine gets ____ in the follicular epithelial cell as it exits into the lumen.
2. In the lumen, I2 binds with ____ and undergoes ______ to make MIT and DIT

Answer 1

oxidized;
Thyrogobulin (TG);
organification

Question 2

T3/T4 synth:
3. in a coupling reaction, DIT + MIT makes ____
DIT + DIT makes ____
4. these are endocytosed into the epithelial cell and undergo _____, releasing T4 and T3

Answer 2

T3, T4;

proteolysis

Question 3

In peripheral tissue, T4 is converted to T3 by _____. which is the more active form?

Answer 3

5’-deiodinase;

T3

Question 4

perchlorate and thiocyanate both inhibit _____

Answer 4

sodium-iodide symporter = decreased uptake

Question 5

_____ is responsible for oxidation, iodination, and coupling of DIT and MIT

Answer 5

thyroid peroxidase

Question 6

type 3 deiodinase metabolizes T4 to ____. what does this do>?

Answer 6

rT3;

nothing (ie rT3 is inactive)

Question 7

_____ inhibits both thyroid peroxidase and 5’-deiodinase. ____ only inhibits thyroid peroxidase

Answer 7

Propylthiouracil (PTU);

methimazole

Question 8

____ is the major carrier of T3/T4 in the blood. T3/T4 carried in this form is _____

Answer 8

Thyroxine-binding globulin (TBG);

inactive

Question 9

high levels of binding protein _____ the rate of degradation. T3 and T4 are conjugated with _____ and sulfuric acids in the liver and excreted into BILE

Answer 9

decrease;

glucuronic

Question 10

T3/T4 binds to what kind of receptor?

Answer 10

intracellular–>regulates gene transcription

Question 11

hypo vs hyperthyroid: which has?

cold intolerance?
hyperactivity + anxiety?
decreased reflexes?
weight loss?
facial myxedema?

Answer 11

hypo;
hyper;
hypo;
hyper;
hypo

Question 12

note: I skipped most of the thyroid disorder pages. look at FA/ICM flash cards for that

Answer 12

you got it dude

Question 13

name 2 thyroid hormone replacement drugs

Answer 13

levothyroxine, triiodothyronine

Question 14

T3 and levothryoxine are used for _____. ____ levels should be monitored

Answer 14

hypothyroidism;

TSH

Question 15

side effects of thyroid hormone replacement:

___Cardia, ____ intolerance, tremors, _____ (heart thing)

Answer 15

tachy, heat;

arrythmias

Question 16

myxedema is usually caused by ____ of the thryoid. it is associated with _____ disease in the heart

Answer 16

destruction/atrophy;

coronary artery

Question 17

PTU and methimazole accumulate in the ____. they are excreted in the urine as _____ conjugates

Answer 17

thyroid;

glucuronide

Question 18

side effects of PTU and methimazole:

skin ___, ____ anemia, ____ toxicity

Answer 18

rash, aplastic;

liver

Question 19

thyroid storm is treated with the 4 P’s:

Answer 19

PTU, propanolol (beta blocker), Prednisolone (corticoids), and Potassium iodide (lugol’s solution)

Question 20

what is the wolf-chaikoff effect?

Answer 20

excess iodine temporarily inhibits thyroid peroxidase = decreased organification = T3/T4 production

Question 21

the Jodbasedow effect is when exogenous iodine causes ____

Answer 21

hyperthyroidism (rare)

Question 22

diatrizoate and iohexol are used in ____ _____ and are potent inhibitors of deiodination, thyroid hormone synthesis

Answer 22

contrast media

Question 23

radioative iodine:
emit beta particles, which _____ the parenchymal cells;
emit gamma-rays, which are helpful for what?

Answer 23

destroy (treat hyperthyroidism;
thryoid scans (diagnostic purposes)

Question 24

radioiodine is contraindicated in ____ due to _____

Answer 24

pregnancy; can destroy fetal thyroid