Thyroid physiology

Question 1

Which hormones does the thyroid secrete?

Answer 1

Thyroxine
Tri-iodothyronine
Calcitonin

Question 2

What number is given to thyroxine?

Answer 2

T4

Question 3

What number is given to tri-iodothyronine?

Answer 3

T3

Question 4

Which hormones does the parathyroid gland secrete?

Answer 4

Parathyroid hormone

Question 5

Which cells within the thyroid are responsible for producing T4 and T3?

Answer 5

Follicle cells

Question 6

Histologically, how are follicle cells described?

Answer 6

simple cuboidal epithelial

Question 7

What structure are the follicular cells surrounding?

Answer 7

Colloid

Question 8

Which cells are scattered around the follicular cells?

Answer 8

Parafollicular C cells

Question 9

What do parafollicular C cells secrete?

Answer 9

Calcitonin

Question 10

Which receptors respond to TSH?

Answer 10

Thyrotopin

Question 11

Describe iodines pathway to the colloid?

Answer 11

Diffuses across the endothelium from capillaries to the follicular cell and diffuses again to the colloid

Question 12

How many units can DIT link to?

Answer 12

2

Question 13

By what mechanism does thyroglobulin leave the colloid?

Answer 13

Pinocytosis

Question 14

How are T3 and T4 released from thyroglobulin?

Answer 14

Enzymatic degeneration by lysosomes which releases thyroglobulin into T3 and T4

Question 15

Which amino acid does iodine attach to in the follicle?

Answer 15

Tyrosine

Question 16

What is formed when iodine and tyrosine attach?

Answer 16

MIT

DIT

Question 17

What is formed when MIT and DIT couple?

Answer 17

T3

Question 18

What is formed when 2 DITs couple together?

Answer 18

T4

Question 19

Where are T3 and T4 stored?

Answer 19

In colloid thyroglobulin

Question 20

Which hormone is the biologically active one?

Answer 20

T3

Question 21

Where is T4 converted to T3?

Answer 21

Liver and kidney

Question 22

Which of the hormones are most abundant?

Answer 22

T4 (90%)

Question 23

What plasma proteins do T3 and T4 bind to?

Answer 23

TBG
TBPA
Albumin

Question 24

Why do T3/4 bind to plasma proteins?

Answer 24

They are hydrophobic

Question 25

What happens when T3 and T4 are bound to plasma proteins?

Answer 25

They are inactive.

Question 26

Does pregnancy increase or decrease T4?

Answer 26

Increases total. No effect on free

Question 27

Does corticosteroids increase or decrease T4?

Answer 27

Decreases total. No effect on free

Question 28

Does hepatitis A increase or decrease T4?

Answer 28

Increases total. No effect on free

Question 29

What effect do anti-epileptics have on T4?

Answer 29

Decrease total. No effect on free

Question 30

Why does hyperthyroidism cause weight loss?

Answer 30

Increased BMR due to increased number and size of mitochondria therefore increased ATP hydrolysis

Question 31

Which hormone, important in children, relies on the presence of thyroid hormones?

Answer 31

Growth hormone releasing hormone and therefore growth hormone

Question 32

Which hormone, used in regulating thyroid hormones, is produced in the hypothalamus?

Answer 32

Thyrotrophin releasing hormone

Question 33

What does TRH stimulate the release of?

Answer 33

TSH

Question 34

Where does TSH live?

Answer 34

Anterior pituitary

Question 35

What does TSH do?

Answer 35

Stimulates release of T3 and T4

Question 36

How is the negative feedback loop closed?

Answer 36

Presence of T3 and T4

Question 37

When are thyroid hormones at their highest levels?

Answer 37

Late at night

Question 38

What causes exopthlamos?

Answer 38

Water retaining carbohydrate build up behind the eyes

Question 39

Physiologically, why might a hypothyroid be cold?

Answer 39

Thyroid hormones involved in thermogenesis.

Question 40

When is propanolol used in hyperthryoidism?

Answer 40

To reduce sympathetic effects e.g. increased HR

Question 41

During pregnancy, what is the effect of the mother being hypothyroid?

Answer 41

Low IQ of baby

Question 42

Which is of greater significance: | Diurnal rhythm in cortisol or in thyroid hormones?

Answer 42

Cortisol

Question 43

Which part of the thyroid connects the right and left lobe?

Answer 43

Isthmus

Question 44

Apart from T3 and T4 what else does the thyroid secrete?

Answer 44

Calcitonin

Question 45

What is the role of calcitonin?

Answer 45

Regulates calcium

Question 46

True or False | An underactive thyroid causes heat intolerance

Answer 46

False. | Causes cold intolerance

Question 47

Which antibodies can interfere with thyroid measurement?

Answer 47

Heterophile antibodies

Question 48

Why does a raised TSH cause hypothyroidism?

Answer 48

Too much TSH causes negative feedback. No TSH then can't release T3/4

Question 49

When is TSH tests not reliable?

Answer 49

If a primary problem with anterior pituitary or hypothalamus

Question 50

If TSH is suppressed what is the condition present?

Answer 50

Hyperthyroid