thyroid physiology Flashcards Preview

Endocrine > thyroid physiology > Flashcards

Flashcards in thyroid physiology Deck (24):
1

what do the parafollicular C cells secrete?

calcitonin

2

where is thyroglubulin stored?

colloid

3

explain the steps in the synthesis of the thyroid hormones?

1. iodine taken up by follicular cells
2. iodine attaches to tyrosine residues on thyroglobulin to form MIT and DIT (building blocks)
3. coupling of the building blocks
4. stored in colloid until required

4

MIT+DIT=

T3

5

DIT+DIT=

T4

6

which thyroid hormone is most biologically active?

T3

7

which thyroid hormone is more potent?

T3

8

in what form are the thyroid hormones biologically active?

unbound

9

what to T3 and T4 bind to?

plasma proteins

10

what molecule to most thyroid hormones bind to?

thyroid binding globulin (TBG)

11

when might there be increased thyroid binding globulin?

pregnancy
new born state
Hep A
Biliary Cirrhosis
taken heroin

12

what will happen to the total T4 when there is increased TBG?

increased total T4 but not free T4

13

what will happen to total T4 when there is decreased TBG?

decrease total T4 but not free T4

14

when might there be decreased TBG?

cushings
acromegaly
chronic liver disease
adrogens

15

roles of thyroid hormones?

increase basal metabolic rate
increase thermogenisis
carb metabolism- increase blood glucose
lipid metabolism- increase lipolysis
protein metabolism- increase synthesis

growth
development of foetal and neonatal brain

normal central nervous activity

16

how do thyroid hormones increase responsiveness to adrealine and noradrenaline?

by increasing number of receptors

17

affect of thyroid hormones on heart?

increase heart rate and stroke volume

18

what stimulates the release of thyroid hormones?

TSH from anterior pituitary

19

what stimulates the release of TSH?

TRH- thyrotrophin releasing hormone from hypothalamus

20

what does stress do to the release of TRH and TSH?

inhibits it

21

when are thyroid hormone levels highest?

at night

22

what can cause a goitre?

gland failure
iodine deficiency

23

symptoms of hypothyroidism?

reduced BMR
slow pulse rate
fatigue, lethargy
slow reflexes
cold intolerance
weight gain
reduced appetite

24

symptoms of hyperthyroidism?

increased BMR
very fast pulse
increased nervousness
insomnia
sweating
heat intolerance
weight loss
increased appetitie