Endocrine System: Thyroid Gland

Question 1

Where is the thyroid gland located? What is the name of the structure connecting the two lobes? How much should it weigh?

Answer 1

located below larynx on each side of and anterior to trachea
isthmus connects the lobes
15-20 g

Question 2

Where is the parathyroid located?

Answer 2

4 rice grains behind thyroid

Question 3

Thyroid gland produces two iodine-containing hormones derived from what amino acid? What are the two hormones?

Answer 3

Tyrosine
T3 (2 tyrosine + 3 iodine)
T4 (2 tyrosine + 4 iodine, more biochemically active but shorter half-life)

Question 4

What is the functional unit of the thyroid gland?

Answer 4

thyroid follicle

Question 5

What is the structure of a thyroid follicle?

Answer 5

follicular cells surrounding a lumen called the colloid

C cells surround follicle and secrete calcitonin

Question 6

What are the 7 steps involved in thyroid hormone synthesis?

Answer 6

1. thyroglobin synthesized in follicular cell and exocytosed into lumen
2. iodide pump actively pumps iodine into follicular cell
3. iodine attached to tyrosine residues on thyroglobin molecules
4. iodinated residues couple to form T3 and T4
5. Thyroglobin is endocytosed and vesicles fuse with lysosomes
6. lysosomal enzymes cleave T3 and T4 which then diffuses into bloodstream
7. iodine (from MIT and DIT) is recycled back into lumen

Question 7

What kind of system is thyroid hormone regulated by?

Answer 7

negative feedback

Question 8

What two endocrine dysfunctions can occur and what are they due to?

Answer 8

hyposecretion (destruction or injury to gland)

hypersecretion (gland tumor, antibody stimulation of glandular tissue)

Question 9

What is a primary dysfunction?

Answer 9

abnormality within gland

Question 10

What is a secondary dysfunction?

Answer 10

gland is normal but is too much/little stimulation

Question 11

How are endocrine dysfunctions commonly treated?

Answer 11

medication to replace hormones or cause atrophy of gland

Question 12

What two structures are considered neuroendocrine?

Answer 12

posterior pituitary and hypothalamus

Question 13

Which pituitary gland secretes a hormone that promotes the growth of soft tissue?

Answer 13

anterior

Question 14

What endocrine gland produces calciferol?

Answer 14

skin

Question 15

What do the substances insulin and glucagon regulate?

Answer 15

rate of glucose uptake and utilization by body