21.3 Thyroid hormones

Question 1

What type of pump is the iodide pump?

Answer 1

2: 1 sodium:iodide symporter.

- sodium potassium ATPase pump

Question 2

Where is iodide more highly concentrated?

Answer 2

in the cell (colloid gland). 30-250x that in the plasma

Question 3

What is used to transport the iodide across the apical membrane?

Answer 3

pendrin: choride-iodide counter transporter

Question 4

How does the thyroid hormone form?

Answer 4

1. thyroglobulin from the thyroid binds up 70 Tyr with iodine to form thyroid hormones

Question 5

Which form of iodide is able to bind with tyrosine directly?

Answer 5

nascent form binds directly (oxidized form)

Question 6

What is the major hormonal product of teh thyroid?

Answer 6

thyroxine

Question 7

What combinations will produce thyroxine?

Answer 7

1. 2 diiodotyrosine joining

2. monoiodotyrosine and dioodotyrosine to form triiodothyronine (T3)

Question 8

Explain the process of how thyroid hormones are released.

Answer 8

1. apical surface pinches off to form the pinocytosic vesicles
2. lysosome fuse with vesicels, digest thyroblogulin molecules, releases thyroxine and triiodothyronine
3. thyroid diffuse into blood

Question 9

What is the majority of thyroid hormone that is released?

Answer 9

1. thyroxine, which slowly deiodinated to form triiodothyronine

Question 10

What is the purpose of the deiodinase enzyme?

Answer 10

1. helps to recycle the majority of iodinated tyrosine in the thyroglobulin during a recycling process

Question 11

What plasma component has a high affinity for the thyroid hormones?

Answer 11

plasma proteins which maintains a high level in the blood and slow diffusion into tissues

Question 12

How does thyroid hormone affect the cardiovascular system?

Answer 12

1. increase blood flow and cardiac output
2. increase heart rate
3. normal arterial pressure (no change)
4. increased respiration

Question 13

How does thyroid hormone affect the nervous and muscular systems?

Answer 13

1. increases excitation of CNS leading to muscle tremors

Question 14

Does thyroid hormone affect the GI?

Answer 14

1. yes, it will lead to increased GI motility

Question 15

How will thyroid affect the metabolic system?

Answer 15

1. initiate carbohydrate metabolism
2. initiate fat metabolism
3. requires increased vitamin in take
4. increase BMR and decrease body weight

Question 16

What type of signaling molecule is thyroid hormone?

Answer 16

1. intracellular; lipophilic signaling. Both T3,T4 can cross membrane. T4 requires iodinase to enter into the nucleus

Question 17

What compounds regulate thyroid secretions?

Answer 17

TSH, cAMP, TRH, cold(immune response), Thyroid hormone feedback

Question 18

Causes of hyperthyroidism?

Answer 18

1. Grave’s disease

2. Adenoma (benign glandular tumor)

Question 19

What are common effects of hyperthyroidism?

Answer 19

1. fatigue
2. inability to sleep
3. tremors
4. exopthalmos (anterior bulging of the eye)
5. psychic disorder

Question 20

What are common causes of hypothyroidism?

Answer 20

1. Hasimoto disease (autoimmune)
2. Endemic goiter
3. Cretinism
   Cause: myxedema, atherosclerosis

Question 21

What does thiocyanate ions Rx do?

Answer 21

inhibit iodine uptake by blocking the I, Na cotransporter

Question 22

What is used to block the I, Na cotransporter system?

Answer 22

thiocyanate ion

Question 23

What drug is used to inhibit peroxidase?

Answer 23

propylthiouracil

Question 24

What is the effect of propylthiouracil?

Answer 24

inhibiting peroxidase uptake

Question 25

What can low levels of deiodinase enzyme simulate or mimic?

Answer 25

similar to iodine deficiency

Question 26

What effects will thyroid hormones have on teh cardiovascular system?

Answer 26

1. increase cardiac output 2. increase HR 3. no effect on arterial pressure 4. increase respirations

Question 27

What will growth hormone do to the GI motility?

Answer 27

increase motility

Question 28

What will growth hormone do to muscles and nerves?

Answer 28

1. increase muscle function | 2. increase CNS excitation

Question 29

How will TSH (thyrotropin) affect thyroid hormone secretion?

Answer 29

1. increase thyroid hormone secretion

Question 30

How will cAMP affect thyroid hormone secretion?

Answer 30

1. increase thyroid hormone secretions and prolong growth of thyroid glandular tissue

Question 31

How will TRH affect thyroid hormone secretion?

Answer 31

1.Secreted from the hypothatlamus to stimulate secretion of TSH. which will increase thyroid hormone release

Question 32

What affect do cold and neurogenic stimuli have on thyroid hormone release?

Answer 32

1. cold/parasympathetic stimulation leads to increased TSH. | 2. Sympathetic stimulation leads to decreases the TSH release

Question 33

What does the thyroid hormone feedback system do to regulate the thyroid secretions?

Answer 33

1. causes inhibition when circulating concentrations reach 1.75 times normal. inhibit TSH

Question 34

What can cause hyperthyroidism?

Answer 34

1. grave's disease | 2. adenoma

Question 35

What are common symptoms of hyperthyroidism?

Answer 35

1. highly excitable 2. heat intolerant 3. increased sweating 4. weight loss 5. diarrhea 6. weakness

Question 36

How is yperthyroidism treated?

Answer 36

1. removal of thyroid gland or treat with radioactive iodine

Question 37

What are commons causes of hypothyroidism?

Answer 37

1. autoimmune (hashimoto) disease 2. endemic goiter 3. crteinism

Question 38

Can myxedema and atherosclerosis be symptoms of hypothyroidism?

Answer 38

yes, corrected with supplemental thyroid

Question 39

What is the effect of thiocyanate?

Answer 39

inhibits uptake of iodine, reducing thyroid T3,T4 production

Question 40

What is the effect of propylthiouracil?

Answer 40

inhibition of peroxidases

Question 41

What can iodides do in high concentrations?

Answer 41

decrease thyroid activity