Growth hormone

Question 1

What factors control growth?

Answer 1

Genetics
Environment
Nutrition
Hormones

Question 2

What is the most important hormone in the control of growth?

Answer 2

Growth hormone duh

Question 3

What produces growth hormone?

Answer 3

The anterior pituitary gland

Question 4

What stimulates the anterior pituitary gland to produce growth hormone?

Answer 4

GHRH from hypothalamus

Question 5

What inhibits the anterior pituitary gland from producing growth hormone?

Answer 5

GHIH/somatostatin from hypothalamus

Question 6

What type of hormone is growth hormone?

Answer 6

Protein hormone

Question 7

What happens to growth hormone protein immediately after it is formed by translation?

Answer 7

Signal peptide is cleaved off

Question 8

Why is it important for the signal peptide to be cleaved off?

Answer 8

So the growth hormone protein can fold up properly

Question 9

How is the CNS involved in the control of growth hormone secretion?

Answer 9

Gives inputs to hypothalamus
Regulating GHRH and somatostatin secretion

which in turn affects GH secretion from anterior pituitary gland

Question 10

How is GH secreted throughout the day?

Answer 10

Pulsatile manner

Question 11

When is the largest amount of GH secreted?

Answer 11

Short while after deep sleep

Question 12

Give four factors that increase GH secretion

Answer 12

Stress - trauma, fever
Exercise
Fasting
Decrease in glucose and fatty acids

Question 13

Give three factors that decrease GH secretion

Answer 13

Rapid eye movement (REM) sleep
Obesity
Increase in glucose and fatty acids

Question 14

What does GH bind to?

Answer 14

GH receptor on cells

Question 15

What is attached to GH receptors?

Where are they located?

Answer 15

Janus kinase enzymes (JAKs)

Intracellularly

Question 16

What hapens when GH binds to GH receptor?

Answer 16

JAKs phosphorylate each other - cross phosphorylation

JAKs phosphorylate GH receptor

Question 17

What does phosphorylation of the GH receptor lead to?

Answer 17

Activation of signalling pathways

Question 18

What do the signalling pathways lead to?

Answer 18

Some lead to activation of transcription factors
IGF genes are transcribed, translated
IGFs proteins produced

Question 19

Where are the IGF proteins produced?

Answer 19

Liver

Skeletal muscle

Question 20

What do the liver and skeletal muscle do with the IGF proteins?

Answer 20

Release them into the blood

Question 21

What tissues do IGFs affect?

Answer 21

All tissues

Question 22

What does IGF stand for?

Answer 22

Insulin-like growth factor

Question 23

What is another name for IGF?

Answer 23

Somatomedins

Question 24

What are the types of IGFs?

Answer 24

IGF1

IGF2

Question 25

IGF1 is the major growth factor in...?

Answer 25

Adults

Question 26

IGF2 is the major growth factor in...?

Answer 26

The foetus

Question 27

What do IGFs do?

Answer 27

Bind to IGF receptors on cells

Question 28

What type of receptor is the IGF receptor?

Answer 28

Tyrosine kinase receptor

Question 29

IGF actions are via...

Answer 29

Endocrine activity But also have autocrine and paracrine effects

Question 30

What does insulin bind to?

Answer 30

Insulin receptor Hybrid receptor Partly to IGF1 receptor

Question 31

What does IGF1 bind to?

Answer 31

IGF1 receptor Hybrid receptor Partly to insulin receptor Partly to IGF2 receptor

Question 32

What does IGF2 bind to?

Answer 32

IGF2 receptor Partly to IGF1 receptor

Question 33

What are the effects of the insulin receptor?

Answer 33

Metabolic effects Some mitogenic effects

Question 34

What are the effects of the IGF1 receptor?

Answer 34

Mitogenic effects Some metabolic effects

Question 35

What are the effects of the hybrid receptor?

Answer 35

Mitogenic effects Some metabolic effects

Question 36

What are the effects of the IGF2 receptor? Why?

Answer 36

None No tyrosine kinase activity tyrosine kinase targets IGF2 receptor for lysosomal destruction

Question 37

What is the hybrid receptor made up of?

Answer 37

Half of the insulin receptor | Half of the IGF1 receptor

Question 38

What are the physiological effects of growth hormone in children?

Answer 38

Stimulates long bone growth length and width before epiphyseal plate closure only width after epiphyseal plate closure

Question 39

What are the physiological effects of IGFs in children?

Answer 39

Stimulate bone growth | cartilage growth

Question 40

What are the physiological effects of GH and IGFs in adults?

Answer 40

Maintain bone mass Maintian muscle mass Promote tissue healing Modulate metabolism

Question 41

What are the effects of IGFs on cells?

Answer 41

Hypertrophy - increase in cell size Hyperplasia - increase in cell number Increased rate of protein synthesis Increased rate of lipolysis in adipose tissue

Question 42

How is GH secretion controlled?

Answer 42

Negative feedback loops

Question 43

What types of negative feedback loops are involved in control of GH secretion?

Answer 43

Long loop Short loop

Question 44

How does the long loop control GH secretion?

Answer 44

IGFs stimulate release of somatostatin inhibit release of GHRH from hypothalamus Also inhibit release of GH from anterior pituitary gland directly

Question 45

How does the short loop control GH secretion?

Answer 45

GH stimulates release of somatostatin inhibits release of GHRH from hypothalamus

Question 46

How are IGFs regulated?

Answer 46

Binding proteins in the blood bind to IGF | modulate its activity - increasing or decreasing it