Thyroid Physiology Flashcards Preview

SM Endocrine > Thyroid Physiology > Flashcards

Flashcards in Thyroid Physiology Deck (35):
1

What all does the thyroid gland tissue secrete?

Thyroxine (T4)
Tri-iodothyronine (T3)
Calcitonin

2

What do the parathyroid glands secrete

Parathyroid hormone (PTH)

3

What cells secrete calcitonin

Parafollicular C cells

4

Describe what can be seen under the microscope for thyroid tissue

Follicular cells
Colloid - tyrosine containing thyroglobulin filled spheres enclosed by follicular cells
Parafollicular C cells

5

What does calcitonin play a minor role in

The regulation of Calcium

6

What is the main substance in the colloid

Thyroglobulin

7

What do tyrosine units do?

Convert T3 to T4

8

How is T3 formed

The coupling of MIT and DIT

9

How is T4 formed

coupling of 2 DITs

10

Where is T3 and T4 found

In the colloid thyroglobulin till required

11

Where is iodine taken up

follicle cells

12

How is MIT and DIT formed

Iodine attaches to tyrosine residues on thyroglobulin

13

What do T3 and T4 bind to and why

plasma proteins as they hydrophobic / lipophilic

14

When are T3 and T4 not biologically active

When they are bound - they need to be released by the carrier as they are required into the tissues

15

Is T3 more active than T4 or other way about

T3 is more active than T4

16

How much of thyroid hormones that are secreted are T4

90%

17

What is the more potent Thyroid hormone

T3 - it is around 4 times more potent

18

What converts T4 to T3

Liver and kidneys

19

What do thyroid hormones do to the basal metabolic rate

Increase it:
increase number and size of mitochondria
Increase oxygen use and rates of ATP hydrolysis
Increase synthesis of respiratory chain enzymes

20

What do thyroid hormones do to thermogenesis

Increase it
around 30 % temperature regulation due to thyroid hormone thermogenesis

21

Why is there an increase in blood glucose because of thyroid hormones

Due to stimulation of glycogenolysis and gluconeogenesis as well as an increase of insulin-dependent glucose uptake into cells

22

What do thyroid hormones do to lipid metabolism

Mobilise fats from adipose tissue and increase fatty acid oxidation in tissues

23

What do thyroid hormones do to protein metabolism

Increase protein synthesis

24

Why is the thyroid hormone important in growth and development

It is important in the production and secretion of growth hormone
Development of foetal and neonatal brain
Normal central nervous activity is controlled by this

25

How do thyroid hormones have a permissive sympathomimetic action

They increase responsiveness to adrenaline and sympathetic NS neurotransmitter, noradrenaline, by increasing numbers of receptors

26

What should be used to treat initial stages of hyperthyroidism

Beta blockers such as propranolol

27

How are the release of TRH and TSH controlled

Through negative feedback of T3 and T4

28

What effect does stress have on the thyroid hormone

It inhibits TRH and TSH release

29

How do low temperatures affect thyroid hormone regulation

Stimulation of TRH release which stimulates TSH release and so increases T3 and T4 release from thyroid

30

Describe the levels of thyroid hormones throughout the day

Circadian rhythm
Highest late at night and lowest first thing in the morning

31

What are some symptoms of a deficient thyroid hormone (hypothyroidism)

Reduced BMR
Slow pulse rate
Fatigue, lethargy, slow response times and mental sluggishness
cold intolerance
tendency to put on weight easily

32

What is another symptom for adults with hypothyroidism

Myxoedema (puffy face, hands and feet(

33

What is another symptom for babies with hypothyroidism

Cretinism (dwarfism and limited mental functioning due to deficiency of thyroid hormones present at birth

34

What causes exophthalmos

Water retaining carbohydrate build up behind the eyes

35

What is the main binding globulin for thyroxine

TBG