Thyroid Guyton

Question 1

The thyroid gland secretes what 3 substances?

Answer 1

thyroxine (T4)
Trridothryonine (T3)
Calcitonin

Question 2

Does calcitonin increase or decrease PTH release?

Answer 2

Decrease (anatognisitc)

Question 3

Which is more potent? T3 or T4

Answer 3

T3 (4x more potent)

Question 4

The cuboidal epithelial cells that line the follicles of the thyroid gland secrete _______ into the interior of the follicle. What is the main constituent of that secretion?

Answer 4

Colloid

Thyroglobulin

Question 5

The thyroid hormones are derived from what glycoprotein?

Answer 5

Thyroglobulin

Question 5

What substance comes from the diet and is an integral component to thyroid hormone synthesis?

Answer 5

Iodine

Question 6

How does iodine get transported into the thyroid cell from the blood? (name of transporter)

Answer 6

Na/I symporter

Moves 2Na and 1 I- into cell

Question 7

What is the name of the transporter that moves the iodine from within the thyroid cell to the follicle? What does the pump remove from the follicle in trade?

Answer 7

Pendrin (I/Cl- countertransport)

Chloride

Question 8

What amino acid does iodine bind to when it enter the thyroid follicle?

Answer 8

Tyrosine

Question 9

What percentage of T4/T3 is protein bound once secreted into the blood?

Answer 9

99%

Question 10

How do thyroid hormones increase cellular metabolic activities? (2)

Answer 10

Increase the number and activity of mitochondria

Increase active transport of ions, notably the Na/K ATPase

Question 11

Can thyroid effect bone growth rate?

Answer 11

Yes
Hyperthyroid children can have increased bone growth early in life.

Question 12

Can thyroid effect brain development?

Answer 12

Yes
Hypothyroid children can have severely retarded mental development

Question 13

How does thyroid hormone effect glucose uptake into cells?

Answer 13

Increases

Question 14

How does thyroid hormone effect glycolysis?

Answer 14

increases

Question 15

How does thyroid hormone effect gluconeogenesis?

Answer 15

Enhances

Question 16

How does thyroid hormone effect general absorption from the GI tract?

Answer 16

Increases

Question 17

How does thyroid hormone effect insulin secretion?

Answer 17

Increases

Question 18

How does thyroid hormone effect fat metabolism?

Answer 18

Stimulates it

Question 19

How does thyroid hormone effect the cardiovascular system? (3)

Answer 19

Increases blood flow and cardiac output

Increases heart rate

Increases heart strength

Question 20

Increased TSH/thyrotropin levels leads to increased secretion of T3/T4 by what ways? (5)

Answer 20

1. Increases proteolysis of thyroglobulin
2. Increases activity of iodide pump
3. Increases iodination of tyrosine
4. Increases size and secretory activity of thyroid cells
5. Increases number of thyroid cells

Question 21

What hormone is secreted by the hypothalamus, which leads to the secretion of TSH?

Answer 21

TRH

Question 22

Which part of the pituitary gland secretes TSH?

Answer 22

Anterior

Question 23

Does cold exposure increase or decrease the rate of TRH and TSH release?

Answer 23

Increase (goal is to increase the basal metabolic rate)

Question 24

Inhibition of TSH release (and subsequent T3/T4 release) is mostly mediated by what?

Answer 24

Elevated levels of circulating T3/T4 levels (negative feedback loop)

Question 25

What is an autoimmune disorder that causes hyperthyroidism?

Answer 25

Grave's disease. Thyroid-stimulating antibodies form and target TSH receptor on thyroid cells. Leads too prolonged activation of cell and continual release of T3/T4

Question 26

What kind of tumor could cause hyperthyroidism?

Answer 26

Thyroid adenoma/adenocarcinoma

Question 27

What is a major cause of hypothyroidism?

Answer 27

Autoimmunity against the thyroid gland (hashimoto disease)