Thyroid Gland Flashcards
1
Q
Thyroid function
A
Synthesises triiodothyronine and thyroxine
2
Q
Thyroid structure (cellular)
A
Follicle
- Follicular cells surround colloid
C cells
3
Q
Follicular cells function
A
Vesicles (enzymes and thyroglobulin) and iodine -> colloid
- Produce enzymes that produce TH
- Produce thyroglobulin (tyrosine residues)
- Transports iodine from plasma to colloid
4
Q
TSH hormone effect on colloid
A
- Endocytoses into follicular cell vesicle (along with proteolytic enzymes)
5
Q
Thyroxine
A
2 tyrosine + 4 iodine
6
Q
Triiodothyronine
A
2 tyrosine + 3 iodine
7
Q
T4:T3 plasma ratio
A
50:1
8
Q
More physiologically active TH
A
T3 (3-5x)
- T4 is deiodinated (50% in plasma, 50% in target cells)
9
Q
Regulation of TH release
A
- Continuous/stable secretion of TRH from hypothalamus.
- AP secretes TSH
- Thyroid secretes TH
10
Q
Increased TRH
A
- Cold
- Exercise
- Pregnancy
11
Q
TSH inhibition
A
- Somatostatin
- Glucocorticoids
12
Q
T4 to T3 conversion inhibition
A
- Glucocorticoids
13
Q
TH functions
A
- Raises metabolic rate (promotes thermogenesis)
- Increases gluconeogenesis
- Increases proteolysis
- Increases lipolysis
- Increases GH receptor expression
- Brain development (in utero)
