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Endocrinology > Thyroid Physiology > Flashcards

Flashcards in Thyroid Physiology Deck (36):
1

Are T3/T4 hytrophobic or philic?

hydrophobic, so bind to plasma proteins

2

What is the biologically active form in plasma protein binding?

unbound

3

Which, T3 or T4 is more avidly bound by Thyroid binding globulins?

T4

4

What is measured at Ninewells, bound or free T4/T3?

free

5

Increased Thyroid binding globulins leads to what happenening to T4?

increases total T4 but not free T4

6

Decreased Thyroid binding globulins leads to what happenening to T4??

decreases total T4 but not free T4

7

Name some conditions where there is increased TBG?

pregnancy
newborn state
Hep A
Chronic active hepatitis
Biliary cirrhosis
Acute intermittent porphyria

8

Name some conditions where there is decreased TBG?

androgens
large doses of glucocorticoids, Cushings
Chronic liver disease
Nephrotic syndrome

9

List 5 thyroid hormone effects related to metabolism.

BMR
Thermogenesis
Carbohydrate metabolism
lipid metabolism
protein metabolism

10

What effect do thyroid hormones have on growth and development?

Growth hormones requires thyroid hormones
Development of foetal and neonatal brain - myelinogenesis and axonal growth
Maintains normal CNS

11

What is permissive sympathomimetic action?

Thyroid hormones increase responsiveness to adrenaline and sympathetic NS neurotransmitter, noradrenaline, by increasing numbers of receptors
also causes cardiovascular responsiveness

12

What is used to treat symptoms in initial stages on therapy for hyperthyroidism due to increased cardiovascular responsiveness?

propranolol

13

What causes TSH to be released from the anterior pituitary?

TRH

14

What causes T3 and T4 to be released from the thyroid gland?

TSH

15

What exert negative feedback control of release of TRH and TSH?

T3 and t4

16

In babies and young children, exposure to cold environments stimulates what?

TRH release, so TSH and then T3 and T4

17

What does stress do to TRH and TSH release?

inhibits

18

What is circadian rhythm?

thyroid hormones highest late at night, lowest in morning

19

Which type of gland failure, primary or secondary, may be associated with an enlarged goiter?

primary

20

If hypothyroidism is secondary to TRH or TSH, is there a goiter?

no

21

May hypothyroidism caused by iodine deficiency be associated with a goiter?

Yes

22

Give 5 symptoms of hypothyroidism.

reduced BMR, slow pulse rate, fatigue, cold intolerance, tendency to put on weight easily

23

What sign is seen in adults with hypothyroidism?

myxoedema (puffy face, hands and feet)

24

What sign may be seen in babies with hypothyroidism?

cretinism (dwarfism and limited mental function)

25

Is hyperthyroidism autoimmune?

yes

26

What happens in Hyperthryoidism?

TSI acts like TSH but unchecked by T3 and T4

27

What sign is seen on eyes and why in hyperthyroidism?

exophthalmos - bulging eyes due to water retaining carbohydrate build up behind eyes

28

List the symptoms of hyperthyroidism.

increased BMR
very fast pulse rate
increased nervousness/emotional
insomnia
sweating and heat intolerance
tendency to lose weight easily

29

What is T4?

thyroxine

30

What is tri-iosinothyronine?

T3

31

Where is TRH released from?

hypothalamus

32

Where is TSH released from?

anterior pituitary

33

What is iodine taken up by?

follicle cells

34

Which is more potent, T4 or T3?

T3

35

Where is T4 converted into T3?

liver and kidney

36

What is the major biologically active thyroid hormone?

T3